Ah, that's too much praise. But thank you anyway! You know, I went to uni a long time ago myself, and now I'm just trying (!) to avoid the mistakes my profs made back then ;-)
Incredibly well nerrated and detailed tutorial on opto-triac couples. Although came here to refresh my knowledge on them, I believe this is an excellent source for beginners. I really admire your work on this one. Please keep releasing such high quality contents. Electronics community needs it.
Robert, many thanks for these detailed explanations and calculations, I understand better the values encountered on the application diagrams. Thanks again for your patience and your explanations. They were very useful.
I thank you for the praise! And I'll will try to keep it up. Though my interests are diverse and I go with my videos where life takes me. It's called a smorgasbord for a reason ;-)
Excellent video tutorial. I have a coffee machine, the Breville BES870XL (US supply 120V 60Hz) that has the Main board pcb with component IS02 which is a MOC3063M. I am still working on the circuit details but there are multiple loads controlled by various Triacs for each of the loads. There are two Solenoid coils, vibratory pump and a grinder motor and the heating boiler. This coffee machine must have been purchased online by an unsuspecting customer here in South Africa and with our 220V 50Hz supply it went poof when switched on... Lol.. then it was refurbished, I have found 220 coils, pump and grinder but the original 120V 1600W boiler is still installed. This machine actually worked like this for two years and has had the coils replaced once due to spool piece corrosion. I have many questions for a multi load application such as this application. Cheers Colin
Thanks! Repairing and converting that Breville coffee machine to 220V is quite a project. Regarding the boiler: Electric boilers are quite sturdy when it comes to running them on too high of a voltage, especially when they are temperature regulated. Anyway, have you though of just adding a diode in series with the boiler to limit the power (heating it with just 220V half waves instead of 120V full waves)?
This video cleared a lot of confusions. The most comprehensive video I watched. Thank you for taking the time to explain everything in detail. Subscribed!
Hi Robert, this is a very nice follow up for your Trilogy 'The Dirty Details'. :-) Very well prepared and presented with all relevant info. I liked it and will build a circuit like this soon. I am currently building my isolation transformer with a 500VA toroidal and 2 5R/5W NTCs for inrush current protection. Great to know how to calculate the various parts. Thank you for producing this video!
Again, thanks for the praise and you're very welcome! Have fun with your big toroidal transformer :-) And be careful with it. They are quite unforgiving when it comes to overloads, shorts etc. But I'm confident that you know what you're doing, since you're already talking inrush current protection ;-)
@darren murphy Ah, the art of calculating the parameters for an NTC! That's not really my forte ... so instead of winging it and you having exploding NTCs I'll refer you to this training module: www.digikey.de/de/ptm/a/ametherm/describing-transformer-protection-from-inrush-current-using-the-ntc-thermistors Hope that helps.
Excellent and Quite informative Video. The best part about your video is, someone fresher like me will be able to understand DATASHEET and its terminology , after watching your video. Most important part for engineer is to understand DATASHEET. I watched your video three times to understand designing part. My Questions is: 1. Can you suggest me more advanced component as compared to MOC3063 and BT139 ? Better and safe solution with zero crossing , advance technology? I an service engineer and at three places, In of my equipment, I observed that HEATER PLATE Crossed 300 degree Celsius, because TRAIC become faulty. and this faulty TRAIC was supplying 230V AC continuously to Heater . In equipment, same HEATER PLATE was used ,which you used in your Video. ( 150 Watt , round shape, which draw less the 1 A current.) Is there any protection circuit in case TRAIC become faulty ? Please guide me , it will be great help.
Well, define "more advanced". The most top of the line zero crossing, TRIAC opto isolator I can think of is the FOD4118 (5kV isolation, can switch 800V). And for TRIACs the sky is the limit: The MCMA650MT1800NKD can switch 650A at 1.8kV. It really depends on your requirements. Regarding "protection circuit in case TRIAC becomes faulty": No, there's no standard circuit for that. In your application I would use a thermal fuse on your heater plate.
@@robertssmorgasbord thank you so much for giving direction for better solution. Sir I have a long query, can I drop you a mail. please share your ID please.
@@sanjaybatra6593 I'm not a professional TH-camr, it's just a hobby of mine. So for privacy reasons I don't give out any contact information. Hope you understand.
Thank you very much for your kind reply, Sir. Actually, I have very much passion for electronics. I am trying to make a Ceiling Fan speed regulator in two ways, one is by using IR remote [(including 7 segments Display+ 2 Push Button+ u-controller (Atmega328 or PIC )+ Diac (For Triggering BT135 from u-c)+ no Optocoupler (4N25 & MOC3021 for Z-C)]. Another way is by using Node MCU/ESP32 (including Optocoupler(4n25 & MOC3021 for Z-C) + BT136 + Blynk app). These thinkings are the study stage at now. For 2nd method (using Node MCU) if I use Only MOC 3041( or MOC3063) instead of using two optocouplers (both 4N25+MOC30) then the circuit will comparatively be simple and economical as well. That's why I asked the previous question. I actually don't know my thinking is right or wrong! but I'm trying. you know MOC 3041 or MOC 3063 which has a built-in Z-C detector option. Besides that if it is possible then there is another problem that is how to connect MOC3041 with u-Controller. I will be very grateful to you if you assist me regarding the above two projects (1st one is quite difficult but I think that is possible) particularly send an email to me (my email is rashed_3e47@yahoo.com) so that I can discuss everything in detail with you about the two projects. Thanks again for replying to me despite your busy schedule.
You've got quite an interesting project there, and I'm tempted to get involved. But please understand that this is just a hobby for me, and between my real job and my spouse I've unfortunately got not time left to work with you on your project. I hope that's not too great of a disappointment to you, but I really don't want to commit to something that I'm unable to go through with.
Thanks for the excellent video. To detect zero-crossing signal by a microcontroller, generally, we use a rectifier then a 4n25 optocoupler, and then a microcontroller. by these detected microcontroller zero-crossing input signal then we use MOC 3021optocoupler/Triac driver to trigger Triac BR136 from the output signal of that microcontroller. My question is Will you tell/Teach us, Mr. Robert's Smorgasbord, that if we use the MOC3041/moc3063 Zero cross Triac driver then can we avoid the above-mentioned arrangement and implement only by a MOC3041(or moc3063) with a Microcontroller to drive an ac load like a ceiling fan.
Thanks for the praise! And thank you for the excellent info! To answer your question: If you just want a simple on/off solution, then yes. That's what I was aiming here for. The zero cross switching here is simply for noise avoidance. If you need phase control, e.g. regulate the speed of the ceiling fan, then no. Though you could implement some speed control by switching on for single half waves.
Great Video, very detailed and easy to follow. I have an application running off a 24VAC generated by a mains powered transformer, therefore already isolated. What will be the risk of driving the TRIACs directly from the uC (supplied by a rectified 24VAC) without isolation from the 24VAC itself? Thanks!
The risk would be that the pin of your uC is exposed to 24VAC through the gate of the TRIAC :-) No, seriously, it's possible. If the power supply of your uC is galvanically isolated from the 24VAC - no problem at all. If you use the same 24VAC to power for the uC you need to make sure in your circuit design, that the aforementioned 24VAC can't get to your uC. Here's an example circuit that does that with AC mains: www-user.tu-chemnitz.de/~heha/Mikrocontroller/Triac8/index.en.htm
... a well pump of 1000w which has a start winding and run winding. Problem is, inrush current is larger than the 5kw inverter can handle. Solar installers recommend a large inverter of 10kW to be able to handle the inrush current which I think is an overkill for inrush current of a few milli seconds. Which is the best way to go to limit the inrush current? Ntc thermistor may also be an option, but repeat start within the cooling off period of the ntc of about 2 minutes will cause another large inrush current. Not sure if ssr zero crossing can be used to switch on/off an inductive load such as a borehole pump.
First, of course you can use zero crossing to switch a borehole pump. But it will not necessarily reduce the total inrush current (just the spike when you switch on with the AC at its maximum voltage). Would it be feasible to "forbid" switching on the pump within 2 minutes after shut off with a little circuit, so the NTC can cool down? If NTCs are not an option, you'll might consider a variable frequency drive that slowly ramps up the RPM. It will set you back a few hundred bucks, but that's still cheaper than a 10kW inverter.
Hi Robert, further to my previous comment, I was wondering whether you would give some thought to do a similar video on a DIY "SPDT" solid state relay (automatic changeover switch), using Triacs and Optocouplers? We regularly have power cuts in a very warm South Africa and rely quite heavily on Solar Power, i.e. constantly switching between an Inverter and the Mains Power Grid (230v) to keep fridges, etc. running. Thanks again for your excellent videos.
Thanks for the awesome video. I really liked you went through all the calculations, I learned a lot. Can this approach also be used to trimmer the resistive AC load with a PWM signal from the MCU or I need to use a phase control circuit? Many thanks in advance
Since the method shown here always switches full half waves, the frequency of your PWM signal needs to be much smaller than your AC frequency. E.g. a 5Hz PWM signal could modulate between 0 and 20 AC halfwaves passing through for a 50Hz AC. If your thinking Arduino, you will have to program such a PWM manually (lots of statements with millis() and micros() 😅).
excellent video - thanks a lot !! I really needed this to create a triac driver for an espresso machine boiler ... exactly 1.5kW, so, I did steal some of the math directly
Hi, great video, I learned a lot doing the calculations. I'm using a moc3041 and a BT136 and I can see that using a different Triac the gate current would be smaller. I have one question which I hope you can answer. Using your circuit, my Hot lead 230vac live is connected to T2, and T1 goes to the load. WITHOUT switching ON the opto-coupler, can I connect a live to T1? WHY I hear you ask, well the opto-coupler circuit is to switch on my heating boiler when the temperature falls below 5degs (a Frost stat) where normally the load is controlled by the timer and temperature setting. So T1 would get it's power when the Gate of the Triac switches on, and also from the household timer.
If I understand you correctly, you're basically shorting out the TRIAC via the timer/temperature switch. Or in other words, you have the TRIAC and the timer/temperature switch in parallel. And yes, you can do that :-)
You're welcome! And please let me know when you've published that tutorial, 'cause I'm currently working on the temperature control of my laboratory water bath ( th-cam.com/video/UHtsRI7svAk/w-d-xo.html ).
Hi, excellent video, I have a couple doubts , Is there any way to measure the sine wave without the isolation transformer? how can I measure the trigger wave from the microcontroller and the AC wave. Regards
First, thank you for the praise! There is a error prone and very dangerous way to measure the sine wave with an earthed oscilloscope without an isolation transformer: Connect your oscilloscope probe ground to mains AC neutral. Make absolutely sure it's connected to mains AC neutral! Make also sure that there is no significant voltage between mains AC neutral and earth in your mains AC installation! Disclaimer: This is not a recommended procedure and if carried out incorrectly can damage your equipment, cause injury and death! I don't think it's possible to measure the signal from the microcontroller and mains AC at the same time with a single oscilloscope without the use of additional isolation equipment (isolated probe, isolation transformer etc.).
Really awesome, thank you. I wonder why an opto-triac must be used in conjunction with another triac for AC switching? Is it because of the limited on-state main-terminal current of the opto-triac?
Thanks for the praise! And you're welcome! Anyway, the answer is yes: The MOC3063 can dissipate at most 150mW and has a maximum on state voltage of 3V. Meaning 150mV/3V = 50mA(effective) is about the maximum that thing can handle continuously. For my 230V AC that's 230V(effective) * 50mA(effective) = 11.5W. That might be enough to switch an LED lightbulb, but not enough for my application.
Would it make a difference if we used 2 parallel 800 ohm resistors instead of 2 series-connected 200 ohm resistors? In series connection, the voltage rating on the resistor is lower. So would it be better connected in series? (And It was a exactly great video, thanks!)
Not really, as long as those 800 Ohm resistors are rated 250Veff AC (in parallel the total voltage rating is that of a single resistor). The only reason I'm using two 200 Ohm resistors in series is to get with cheap 1/4W resistors a voltage rating of 250Veff AC (yes, in series the voltage ratings of resistors of the same value add up). You could also just use a single 400 Ohm resistor that has a voltage rating of 250Veff AC.
Hi, very nice explanations. I am designing a circuit to control roller shutters using Arduino (or ESP8266, not sure yet). So a 5V or 3.3V circuit. So for 3.3V, Rled will be 240R and for 5V, Rled will be 430R. As it is an inductive load (but with a power factor >0.95 as stated in the datasheet of the motor), I will use a BTA16-600BW (snuberless) as triac with a very small heatsink. I will add a resistor between the gate and M1 as suggested in your video. Do you think that 330R is OK? The motor is controlled by 2 phases (up and down). Of course, they must not be on the motor at the same time. I will first turn off one phase before turning on the second phase. the triac will turn off at exactly zero crossing, BUT the other triac might turn on before the first is off as seen on your oscilloscope. I can then wait more than 10ms before turning on the triac after turning off the first triac. But is it a hardware way (interlock) to prevent the turning on of one phase if the other is not off yet? Thank you
The peak gate current of the BTA16-600BW is 4A. So at 230 V (peak voltage +10% 358 V) you should be fine with 330 Ohm (aboutish 1 A). You could use some external logic chips to implement a hardware interlock. The logic functions would be: 1. optocoupler: [mcu 1. optocoupler pin] AND NOT [mcu 2. optocoupler pin] 2. optocoupler: [mcu 2. optocoupler pin] AND NOT [mcu 1. optocoupler pin] So you would need two inverters and two AND gates (the outputs of the AND gates driving the optocouplers of course).
I do enjoy your deep dive stuff like this very much, but I no youtubers don't like " requests" so this is a "if you fancy it and get a moment" semi request thingy, I would like you to explain ADC's, maybe with the popular cheap module ADS1115, at the moment I'm interested in measuring small voltages and currents. Perhaps you already had this in mind or simply don't like the idea but please keep your explanations and tutorials coming they are much appreciated by me and many others...cheers.
Hi andymouse123, I was already thinking about doing some ADC and DAC stuff. The reason being Arduinos lackluster 10 bit ADCs and its total lack of DACs - you don't always want to fiddle around with the PWMs. I can't promise that I'll use an ADS1115 or when exactly I come around doing that video, but it's definitely in the queue now.
@@robertssmorgasbord Oh, that's great! I look forward to that, im finding the subject very interesting, in fact the whole world of power supplies, test and measurement etc...cheers.
Hello Robert! Awesome and clear video. Can you explain your testing setup a little more? I am looking into analyzing some problems in my TRIAC circuit with an oscilloscope but have been running into warning on every single forum about measuring mains voltage with an oscilloscope. Thank you! Karim
Read manual of the osciloscope how to connecto AC, its definetely there. Something like swithing on probe to x10 divider and click auto-adjust on the osciloscope - and you should se the sine wave. You can use transformer to work with safe voltage (< 30VAC), e.g. www.aliexpress.com/item/4000668357474.html or any other low AC transformer.
@@sindbadoo BNC connectors are connected to earth. It's not as simple as just put it on 10X. There are multiple safe ways to do it, two of which are using an isolation transformer (NOT ON THE OSCILLOSCOPE, rather on the device under test (DUT)), and the other using high voltage differential probes (still useful either way). I'm asking about the particular setup Robert had. I see an isolation transformer (that APC), but that doesn't tell me how he setup the entire thing, which is what I'm interested in.
Hello Karim! I supply the TRIAC circuit from an isolation transformer (the big black box with the bluish display - see "Small Project: AC Mains Isolation Transformer from Two Broken UPSs" th-cam.com/video/SlTDqRNryuM/w-d-xo.html th-cam.com/video/SmCYR4FNrSs/w-d-xo.html - of course you can buy one) with 230V. So the 230V within the TRIAC circuit have no potential to / are isolated from mains AC earth. This way I can connect the ground of the oscilloscope probes, which are indeed connected to mains AC earth, anywhere in the circuit without causing a short from mains AC live to mains AC earth, which might destroy the circuit and the oscilloscope. And you're welcome!
Hi there. I loved the video. I like how you explained the circuit design so simplistically. I was wondering if you mind making a video on snubber circuit designs (specifically for random crossing opto-couplers) and possibly addressing the pros and cons of using a zero-crossing optocoupler verses a random phase optocoupler.
Hi Vutivi, I usually do these tutorials for stuff I actually plan to use in my projects. Currently I have no project coming up in need of switching an inductive load with a TRIAC, that is in need of a snubber network. Same holds true for switching TRIACs at random phase angles. However, as soon as I'll need these things there will be related tutorials - no promises though.
Just to make an observation supporting this request: you put a tremendous work to cover the triac application area. I think the crown will be placed on your work if the very last part will be published: controlling inductive load by triacs. Unfortunately very few material can be found on the net about this topics comparing to the other application areas. Desiging the scrubbing on the optocoupler and the triac side seems an other science therefore your detailed explanation and presentation on this field would be valuable. Thank you for all the work you invested in this area and I hope one day you really need to control an AC motor.
Fantastic video! I know you made this a while ago, but if you have time would you please consider a supplementary video with information about implementing a snubber circuit for switching inductive loads? Thank you!
Thank you for the praise! Regarding inductive loads and snubber networks: I'll put it on my wall of video ideas - no promises though. But I do have one question: Do you want switch your inductive loads on zero-crossings only, or do you intend to implement some phase control?
@@robertssmorgasbord I want to switch 24VAC sprinkler solenoids. My first attempt used mechanical relays and had all kinds of electrical problems when they switched off. Then I added a snubber and those problems went away, but now that I've learned more I want to move to triacs (i.e. something without a mechnical switch). For my application, switching on zero-crossing seems to be the solution, but you pointed out in your video that the zero-crossing triac-output optocouplers don't necessarily switch at zero, and my load being inductive will feed some current back into the circuit. I'd like to learn how to properly implement a snubber on this kind of circuit with a triac. Thanks again!
@@BrianDoylePDX There are indeed cases where a zero-crossing triac-output optocoupler might switch on not at zero. But these are worse case scenarios (like the AC power is coming on at the peak of the sine wave). Of course you have to dimension your circuit for it (in the video the gate resistors), but I don't think with 24VAC solenoids it will cause any issues. There are also snubber-less triacs available (they can take the voltage peaks from an inductive load without uncontrolled retriggering) like the ST T435T-600FP (4A, datasheet specifically mentions switching valves ;-) ) or the BTA208X-1000B (8A). How much current do your solenoids draw?
Hi Robert. Great video. Unfortunately, I still can't understand how you calculated the 80mW current across the current limiting resistor. More. Usually, there is another resistor between the gate and one of the anodes with a value similar to the value of Rg. What about its current and voltage specs? Thanks in advance!
Thanks for the praise! What step(s) exactly of the calculation for the power dissipation of RG ( th-cam.com/video/rLpFtSayZ3Q/w-d-xo.html ) is/are unclear to you? The sometimes used additional resistor between the gate and T1 (never T2!) is only necessary in noisy environments (e.g. switching high power brushed motors). It "shorts" unwanted voltage/current spikes at the gate to T1 and thus prevents unwanted triggering of the Triac by noise.
@@robertssmorgasbord Thank you for your prompt reply. Actually, I can't understand from where you get tGT and the bottom value: 2us/10ms values. I use BTA12-600BW for my switch. Thanks
@@NaudioElectronics Let's start with the 10ms. That's 1s / (50Hz * 2), or the time between trigger events if you want the TRIAC to be switched on all the time. For 60 Hz it would be 1s / (60Hz * 2) = 8.3ms. t(GT) is the time the TRIAC needs to become conductive after being triggered, and thus the time current actually flows through the gate. And indeed, ST is not specifying that for the BTA12 in the datasheet 😞 But I'm sure if you use 2 0.25W resistors in series as I did, you'll be fine. Hope that helped!
Thank you very much! I don't know about "excellent" :-) I'm just striving for correct and - if possible within the context of a video - complete information about a given subject.
The "APC" device shown in the video is actually not an an device from APC 🙂 It's an isolation transformer that I build from two defect APC uninterruptable power supplies (UPSs), reusing one of the enclosures and both of the transformers: th-cam.com/video/SlTDqRNryuM/w-d-xo.html , th-cam.com/video/SmCYR4FNrSs/w-d-xo.html . But any commercially available isolation transformer will do the job, probably even better😉
Great video. Should I use a zero crossing optocoupler or a zero crossing power triac or both? my waveform is very interesting I wish I could upload a picture of it.
Thanks! Well, if you find a zero crossing power Triac, and you don't need the galvanic isolation the optocoupler provides, then you could of course use that zero crossing power Triac. Please let me know the type of Triac you have in mind.
Thank you for the reply. My power triac is nothing special. It is a 600 volt 20 amp. It is random fire. Also, I do need the isolation so the optocoupler is definitely necessary. I obtained a few zero crossing triac optocouplers today and the sine wave is now extramely clean. The power triac is still random fire but it is impossible to tell. The zero crossing driver is correcting the zero crossing for the random fire power triac. The transition is perfect. Now I need to apply all of your math to ensure it will last. Awesome video. I learned a lot and will use what you have taught me frequently. Chris.
Great video. One thing that i can't undestand is when i created a PCB with this schematic but somehow switched triac terminals T2 and T1 then circuit was not working. Do you have any idea why this is happening? I though triac is biderectional. Also could you please make another video with calculation of the resistor between gate and T1? does it also affect the value of Rg resistor?
Thanks! While TRIACs work bidirectional in regards to T1 and T2 they are NOT symmetrical in regards to G and T1, respectively G and T2. The voltage at G is ALWAYS referenced to T1. In other words, the voltage between G and T2 doesn't matter when it comes to triggering the TRIAC. See also the links in the video description "TRIACs - The Dirty Details ...". So I fear you will have to make another PCB where you have T1 and T2 connected correctly. As for the value of Rg ... I went over the calculation of its value at 09:38 - what exactly is your question?
@@robertssmorgasbord thank you for the reply. I think i understand now. I will rework the PCB. For the resistor I did not mean the Rg resistor calculation but the one which puts t the gate down to prevent false triggering (not in your schematics). The resistor between the gate and T1.
@@Mikomanus You're welcome! Regarding your question, have a look at electronics.stackexchange.com/questions/248743/how-is-the-gate-trigger-resistor-value-calculated-for-a-triac . That resistor between G and T1 is usually not required (that's why I didn't use it). You might need it if your TRIAC triggers at very low currents and you are in a very noisy environment.
Can you explain in more detail the purpose of a resistor between A1 and G? I have a very similar circuit to the one in this video, VACrms = 120VAC, Rg = 360 Ohm, the load is inductive, and it includes a Rn = 360 Ohm resistor between A1 and G. I'm having issues with the Rn getting extremely hot!
The purpose of the resistor ("Rn") between the gate ("G") and the terminal 1 ("A1"? Did you mean "T1"?) is to conduct induced currents - or simply noise - away from the gate. Remember, the gate trigger voltage can range from just a few hundred millivolt to a little over a volt! So even small voltages induced through magnetic fields (e.g. large electric motors) or electromagnetic noise (e.g. arc welders) can cause the TRIAC to trigger, if they are strong enough to induce a current of a few milliamps for a few microseconds. In your case the "noise" would have to induces a current of 1.4mA through that resistor first before a typical gate trigger voltage of 500mV is reached (500mV/360Ohm).
Robert Smorgasbord, why does increasing or decreasing loads resistance value will change Triacs Or SCR "holding current" and Passing Current?How can you bias a triac or SCR using Negative Bias?
Sorry, but I don't quite understand your question. If you decrease the load resistor value, naturally the current through the Triac will increase (Ohm's law) and vice versa. As for the holding current: It doesn't change with the current through the Triac. It's just when the current through the Triac falls below the holding current, the Triac will stop conduction. That is the current goes to zero. As for negative bias: What exactly do you want to negatively bias? The gate? The main terminals? And what do you want to achive with that negative bias?
Some Triac can negative bias the main terminals but the gate is positive bias or the triacs main terminals are positive bias and the gate is negative bias. What are the difference between how the terminals and gate are biased?
@@waynegram8907 Ah, now I get :-) The holding current of a Triac is purely determined by its silicon structure, that is the size/geometry of the different N- and P-layers. See also "TRIACs - The Dirty Details (1/3): Gating, Latching and Holding" th-cam.com/video/I69Fiy3IwBE/w-d-xo.html And SCRs do have a holding current I(H) too ;-)
Hi Robert, with a zero crossing opto, if we switch an AC synchronous motor on the neutral side (Phase--->Motor---->Triac---->Neutral) , is there a way to figure out which quadrant the triac is operating at ? I am using 2 uC pins to drive a synch. motor in forward and reverse direction with 2xBT136 and MOC3041M.As you might have guessed, I am facing a lot of triac failures :( . An appnote I was reading "Thyristor and Triacs Ten Golden Rules " mentions avoiding triggering in 3+ quadrant (MT2-,G+) as one of the golden rules.
Figuring out in which quadrants your TRIAC is working shouldn't be a problem. But I need to know a little more about the circuit: Is the TRIACS T1 connected to neutral or to the motor? Respectively, is the TRIACS T2 connected to the motor or neutral? Where is the 2nd pin of the optocoupler connected (assuming the first one goes via a resistor to the gate of the TRIAC) - between the motor and the TRIAC, directly to phase or directly to neural?
@@robertssmorgasbord Hi Robert, Thanks for your reply. MT1 is connected to Motor, MT2 is connected to Neutral. Pin 4 of the Opto goes directly to Gate (no resistor). Pin 6 of Opto goes to MT2 (Neutral) through a 470E resistor. There is a 470E resistor directly across the Gate and MT1.
@@mumbaiverve2307 Looks good, your triggering with MT2+/G+ and MT2-/G-. Questions: How big is you synchronous motor? Do you have you an RC snubber network in place (motors are inductive loads!)? Is the heatsink for your TRIAC large enough?
@@robertssmorgasbord Hi again , the motor is very small , 0.003HP (125mA). It can rotate in both directions. Hence there are 2 ZC Opto/ Triac combination triggered from 2 uC pins. There is a RC network on the motor, I dont know if it does only snubbing or also meant to create a phase difference for the motor to rotate (like Capacitor on fans). There is no snubber network on the PCB across the MT1/MT2,though.
Again, no such thing as a silly question 😉 In that video I connected the oscilloscope probes just across the load (see red arrows here: th-cam.com/video/rLpFtSayZ3Q/w-d-xo.htmlsi=H_jZpEFONajM_lWA&t=1988 ). It doesn't matter which way around, since we're measuring AC. WARNING: You're oscilloscope ground is usually connected to the AC mains ground. So without galvanically isolation your circuit (I'm using a transformer here), you might create a short and create a big bang!
Hi, I have an electronic board to control an AC motor -2500 watts/220v. On the board are mounted two TRIAC - BTB24-600BW . The motor has a problem-runing on reverse only-no matter which button is pressed-FW or RW. I found that the resistor who is connected to the Gate terminal on TRIAC 1 is burned and I replaced with a new one 47 Ohm/1 w . Also I found a short cut between the Gate and Terminal 2 (the midle terminal) on the same TRIAC and replace it with new TRIAC--BTB24-600BW.After that I did a check by multimeter between all soldering points. Then the board was connected to the motor.Unfortunatly the motor not run-in any directions- clock wise or reverse ! Do You can to gave me any advice?
Well, without knowing the whole circuit and the type of the AC motor (I'm assuming it's a single phase universal AC motor) it's quite hard to give some advice. For example: Are your sure the burned out gate resistor was 47 Ohm? Because that would give you a peak gate current of 220V*1.41/47Ohm = 6.6A, while the BTB24 is only rated for 4A peak gate current. Also, how does the FW/RW button/circuit work? Anyway, if you desolder the BTB24 again and just solder in a (reasonable thick) wire between terminal 1 and terminal 2, then the motor should run at full speed as soon as you connect the circuit to AC mains. If that's not the case, than something else beyond the TRIAC has been damaged.
Sorry for the late answer. I don't know what kind of swing motor you have in your air conditioner. But normally those are relatively low powered synchronous AC mains motors (two wires) or low voltage DC stepper motors (at least four) wires. The latter you obviously can't switch with an TRIAC. But since you mentioned a relay I guess it's the former. And that you can switch with a Triac without any problems - AC is AC, whatever the load is. However, since it's an inductive load (motor coils) you might need to add a snubber network (resistor and capacitor) to my circuit, as it is shown in this article (figure 3): www.nutsvolts.com/magazine/article/triac_principles_and_circuits_part_1
Well, unfortunately there's not a short answer. Have a look at that application note (18 pages): www.st.com/resource/en/application_note/cd00004096-rc-snubber-circuit-design-for-triacs-stmicroelectronics.pdf
Yes, it is possible, and yes, it makes a difference. Please note that in this case the TRIAC-optocoupler also has to be AFTER the load, otherwise you'll get excessive gate currents. Regarding the differences see that thread on the ST Microelectronics forum: community.st.com/t5/power-management/which-pin-should-drive-triac-load/td-p/290881 (NOTE: The drawing posted there by the user asking the question is wrong! T1 and T2 are swapped in that drawing.)
@@robertssmorgasbord Thanks for your reply. Right now I have my load on the MT1 line. I have built a PID oven controller and it is working well. But still in development. I asked about this because I have read that the load should be on the MT2 side but all the example circuits, including yours are on the MT1 side. So if I put the load on the MT2 side the pin for the MOC3023 opto should be between the load and the MT2 connection? NOT before the load. Is that correct? I'll probably just leave it as it is because it's working but it would be good to know. Cheers Matt
@@TYGAMatt Yes, if you connect the load to MT2, then one pin of the optocoupler needs to be connected between the load and MT2. The reason being, if the TRIAC is triggered, the voltage drop across the load will limit the current through the optocoupler, the gate resistor and the gate. I have to ask, where did you read that the load should be on the MT2 side? There are no advantages to that, only drawbacks.
You calculated resistor power to be 80mW. So why not just use one 390R 0.25W resistor? Why use two 0.25W 200R? Isn't one 0.25W still a lot bigger than 80mW?
0.25W resistor are usually rated for up to 350V. But the maximum peak voltage on European AC mains is (230V + 10%) * sqrt(2) = 358V. So it's better to use two of those 0.25W resistors in series (when they have equal values the rated voltage is then 350V * 2 = 700V) to be on the safe side.
Switching inductive loads on is not problem. You don't need necessarily zero crossing to avoid noise when doing that to do that (though it doesn't hurt), the inductor itself will limit the switch on current. Switching an inductive loads off without causing noise/spikes is the problem, and zero crossing doesn't help with that. Usually a RC snubber network is added when handling inductive loads to ensure the TRIAC really switches off and voltage spikes are absorbed.
If you put resistors with the same value (resistance) and the same voltage rating in series, than you can add their voltage ratings together as the combined voltage rating. I only mentioned the single 2W resistor, because 2W types were the only ones I could find with a voltage rating above 358V. I ended up using two 0.25W resistors with a voltage rating of 200V in series, because combined they have a voltage rating of 400V. Besides, I calculated the power loss as 80mV, so using a 2W resistor seemed a bit wasteful.
@ 13:17 I really wonder how did you get a 358 Ohms resistor value? because 358V divided by 2 is 179 Ohms. its not clear even how did you get 1 in case of other ideas, so 358V divided by 1 is 358 Ohms, Still don't understand how did you get 1 there.
The 1A is the current maximum of the optocoupler ;-) Since it's in series with the Triac's gate, the maximum current is the minimum (1A) of what the optocoupler (1A) or the Triac's gate (2A) can take.
@@robertssmorgasbord Still confusing indeed. can you tell me the value of the gate resistor for this triac (BTA41-600BRG) with the same optocoupler you are using?
@@MicrosiMe The BTA41 can take according to the datasheet a peak gate current I(GM) of 8A, which doesn't matter, because the peak repetitive surge current I(TSM) of the MOC3036 optocoupler is still just 1A. So the minimal gate resistor value, calculated for the 1A the optocoupler can take and 230V AC +10%, is still the same 358 Ohm. The optocoupler simply can't provide more gate current to the Triac. Anyway, if you're want to use a BTA41 you might wanna think about using an optocoupler that has a higher peak repetitive surge current I(TSM). The reason being that the BTA41 needs a whopping 50mA to trigger (maximum gate trigger current I(GT) quadrants I to III). The BT139 needs just 10mA there. So with the same gate resistor the BTA41 will trigger considerable later than the BT139 after the zero crossing of the AC voltage.
In theory absolutely nothing. The output side of that optocoupler (pin 4 and 6) is an AC device after all. The polarity at its pins changes with 50Hz/60Hz anyway. If you had a very close look with an oscilloscope you might see some subtle changes, since the TRIAC / zero crossing circuit within the optocoupler would be operating in different quadrants. But we're talking very small changes in the timing.
With the TRIAC you've got a voltage drop of about 1.3V. Assuming you run your load at 230V AC your RMS current is 7500W / 230V = 32.6A. So your power loss would be 1.3V * 32.6A = 42.4W. Please note that the power loss in a TRIAC scales linearly with the current. With MOSFETs (see e2e.ti.com/blogs_/b/industrial_strength/archive/2016/07/26/a-modern-approach-to-solid-state-relay-design ) your power loss scales with the square of the current: P = I^2 * R. R being the on resistance of the MOSFETs. To have the same power loss as with the TRIAC solution we need R = P / I^2, 42.4W / 32.6A^2 = 40mOhm. And that's for both MOSFETs. So a single MOSFET would need to have a on resistance of 20mOhm. You can get those, but they are expensive (e.g. IPZ65R019C7XKSA1 $20 19mOhm). If you want to half the power loss compared to the TRIAC you could use UF3SC065007K4S $64 9mOhm. You can't get better than that. So in your application I would go with the TRIAC as shown in the video. But of course you could spent $130 for MOSFETs and half the power loss.
@@robertssmorgasbord but these losses have something to do with zcd? because I saw others project that looks try a real zcv. using mcu calculation th-cam.com/video/P6mbBJDIvxI/w-d-xo.html. the losses in the tric is just the current x volt of 2diode? like 1.3V x 32A? Or have to do with the cvd pf the optocouplers? my Idea is control a electric shower 7500w and 220v. and I want all cheap parts and less losses possible. I was thinking in moc triac, lm35, pic 16f877,
@@ronaldo0grande No, these losses have absolutely nothing to do with zero cross detection (switching). These are the losses for the TRIAC / MOSFETs fully on for each full half wave. And yes, the losses in the TRIAC are just current x voltage drop over the TRIAC (approximately 2 diodes) - for the TRIAC being on for each full half wave. The zero scross switching is really just there to avoid noise. So your cheap solution will be absolutely fine. If you want to control the power your microprocessor can switch the TRIAC on for defined intervals. Say from 20ms on / 80ms of (20% power) to 100ms on / 0ms off (100% power) - basically a pulse width modulation. Please note that the on time should be larger that 10ms for 50Hz AC, otherwise there's a chance you miss the cero crossing for switching on completely.
Paralleling TRIACs or SCRs is a really bad idea. One will trigger first. So the others will not trigger at all, being basically shorted out by the one that triggered first.
I see tutorial of making soft starter using triac that arrange pararel, this is the link th-cam.com/video/s7dKrFWPC10/w-d-xo.html, is it work to make triac bt139 parrael like that video, or it only one triac that work like you said. The video maker said that it will multiply the ampere of the triac. Is it true?
@@HITESHTHAKOR-js2dh The datasheet of the optocoupler ( optoelectronics.liteon.com/upload/download/DS70-2001-026/MOC306X%20series%20Mar19.PDF ) is of course valid for every use of that optocoupler, not only for its use in conjunction with a TRIAC. Other optocouplers have of course their own datasheets and different specifications. Hope that answers your question.
Yes you can. The BT139-800E can handle the 10A. You just have to roughly double the size of the heatsink, respectively choose a heatsink with roughly half the thermal resistance.
I was always under the impression that Australia uses 230Veff too. But now I'm confronted with you telling me ... That's not a mains AC voltage, THAT'S A MAINS AC VOLTAGE 😅
@@robertssmorgasbord It was just a bit funny you way said it. It was a good video though. We are supposed to have 230v but it’s usually 240vac often up at 250vac in practice.
@@SparkyJames Here in Europe mains AC is nominally 230V +/- 23V (10%). So we're also seeing voltages up to 252V. Both, the circuit and the TRIAC can take that - so they're save for Australia 😅 And thank you for the praise!
Unfortunately, you failed to show a varying input logic signal and how that affects the power switched to the load. This is how these devices are used in real world application ... sometimes as a 'relay' but more often as a time-gated power controller.
The title of the video does contain the phrase "Zero Crossing Triac Output Optocouplers". I'm assuming with "time-gated power controller" you are referring to phase control. A zero crossing TRIAC output optocoupler is generally used to avoid switching during the positive or negative phase (which would be phase control). That in turn avoids current spikes and switching noise. If you want to see phase control have a look at "TRIACs - The Dirty Details (3/3): Practical Considerations" th-cam.com/video/jjTr7DD2ouE/w-d-xo.html .
![How to reuse Washing Machine Motors [Arduino vs Basic Triac control]](http://i.ytimg.com/vi/xI6CF2nYf_g/mqdefault.jpg)
This video is literaly more educating than almost my entire university lectures. Great explenations, great clearifications.
Ah, that's too much praise. But thank you anyway! You know, I went to uni a long time ago myself, and now I'm just trying (!) to avoid the mistakes my profs made back then ;-)
Incredibly well nerrated and detailed tutorial on opto-triac couples. Although came here to refresh my knowledge on them, I believe this is an excellent source for beginners. I really admire your work on this one. Please keep releasing such high quality contents. Electronics community needs it.
Thank you very much! I will do my best to keep the tutorial style videos coming.
Robert, many thanks for these detailed explanations and calculations, I understand better the values encountered on the application diagrams. Thanks again for your patience and your explanations. They were very useful.
Again - already relied to your comment on "TRIACs - The Dirty Details (1/3)" ;-) - you're very welcome!
Months of unanswered questions about triac gate resistance and yes now I am satisfied with your answers. Thank you so much for this awesome tutorial.
I'm happy my video answered your question about the gate resistance. And I thank you for the praise.
Thanks Robert! This is the most comprehensive and best explanation of the subject that I have ever seen! Please keep this up.
I thank you for the praise! And I'll will try to keep it up. Though my interests are diverse and I go with my videos where life takes me. It's called a smorgasbord for a reason ;-)
Robert, Thanks for going into all this detail. It really does help to know the details that we may decide to overlook most of the time!
You're welcome! Most of the time it's totally OK not to care about the details, but sometimes a overlooked detail can mess up everything ;-)
Excellent video tutorial. I have a coffee machine, the Breville BES870XL (US supply 120V 60Hz) that has the Main board pcb with component IS02 which is a MOC3063M. I am still working on the circuit details but there are multiple loads controlled by various Triacs for each of the loads. There are two Solenoid coils, vibratory pump and a grinder motor and the heating boiler. This coffee machine must have been purchased online by an unsuspecting customer here in South Africa and with our 220V 50Hz supply it went poof when switched on... Lol.. then it was refurbished, I have found 220 coils, pump and grinder but the original 120V 1600W boiler is still installed. This machine actually worked like this for two years and has had the coils replaced once due to spool piece corrosion. I have many questions for a multi load application such as this application. Cheers Colin
Thanks! Repairing and converting that Breville coffee machine to 220V is quite a project. Regarding the boiler: Electric boilers are quite sturdy when it comes to running them on too high of a voltage, especially when they are temperature regulated. Anyway, have you though of just adding a diode in series with the boiler to limit the power (heating it with just 220V half waves instead of 120V full waves)?
This video cleared a lot of confusions. The most comprehensive video I watched. Thank you for taking the time to explain everything in detail. Subscribed!
Thanks for the praise and subscribing!
Excellent tutorial, thank you.
You're very welcome 🙂
This is the best video I've found on the subject. Just subscribed. Thanks!
Thanks for the praise and subscribing! And you're welcome!
Great detailed video! Thank you! This is why a lot of people use the complimentary SCR circuitry.
Thanks! And you're right. What you also see quite often is a full bridge rectifier with a SCR to switch AC.
Hi Robert, this is a very nice follow up for your Trilogy 'The Dirty Details'. :-) Very well prepared and presented with all relevant info. I liked it and will build a circuit like this soon. I am currently building my isolation transformer with a 500VA toroidal and 2 5R/5W NTCs for inrush current protection. Great to know how to calculate the various parts. Thank you for producing this video!
Again, thanks for the praise and you're very welcome!
Have fun with your big toroidal transformer :-) And be careful with it. They are quite unforgiving when it comes to overloads, shorts etc. But I'm confident that you know what you're doing, since you're already talking inrush current protection ;-)
@darren murphy Ah, the art of calculating the parameters for an NTC! That's not really my forte ... so instead of winging it and you having exploding NTCs I'll refer you to this training module:
www.digikey.de/de/ptm/a/ametherm/describing-transformer-protection-from-inrush-current-using-the-ntc-thermistors
Hope that helps.
thorough explanation, thanks a lot
You're welcome! And thanks for the praise!
Finally some one explain correctly all this things. Thanks !!!!
You're welcome! And thank you for the praise.
@@robertssmorgasbord thanks to you for your time and generosity making and sharing this video. Is very helpful for my. Greetings from Argentina
Excellent and Quite informative Video.
The best part about your video is, someone fresher like me will be able to understand DATASHEET and its terminology , after watching your video.
Most important part for engineer is to understand DATASHEET.
I watched your video three times to understand designing part.
My Questions is:
1. Can you suggest me more advanced component as compared to MOC3063 and BT139 ? Better and safe solution with zero crossing , advance technology?
I an service engineer and at three places, In of my equipment, I observed that HEATER PLATE Crossed 300 degree Celsius, because TRAIC become faulty.
and this faulty TRAIC was supplying 230V AC continuously to Heater .
In equipment, same HEATER PLATE was used ,which you used in your Video. ( 150 Watt , round shape, which draw less the 1 A current.)
Is there any protection circuit in case TRAIC become faulty ?
Please guide me , it will be great help.
Well, define "more advanced". The most top of the line zero crossing, TRIAC opto isolator I can think of is the FOD4118 (5kV isolation, can switch 800V). And for TRIACs the sky is the limit: The MCMA650MT1800NKD can switch 650A at 1.8kV. It really depends on your requirements.
Regarding "protection circuit in case TRIAC becomes faulty": No, there's no standard circuit for that. In your application I would use a thermal fuse on your heater plate.
@@robertssmorgasbord thank you so much for giving direction for better solution. Sir I have a long query, can I drop you a mail. please share your ID please.
@@sanjaybatra6593 I'm not a professional TH-camr, it's just a hobby of mine. So for privacy reasons I don't give out any contact information. Hope you understand.
At last, a very good video explaining everything in simple terms.... Thank you. 👍
I thank you for the praise! And you're very welcome!
Thank you very much for your kind reply, Sir.
Actually, I have very much passion for electronics. I am trying to make a Ceiling Fan speed regulator in two ways, one is by using IR remote [(including 7 segments Display+ 2 Push Button+ u-controller (Atmega328 or PIC )+ Diac (For Triggering BT135 from u-c)+ no Optocoupler (4N25 & MOC3021 for Z-C)].
Another way is by using Node MCU/ESP32 (including Optocoupler(4n25 & MOC3021 for Z-C) + BT136 + Blynk app). These thinkings are the study stage at now. For 2nd method (using Node MCU) if I use Only MOC 3041( or MOC3063) instead of using two optocouplers (both 4N25+MOC30) then the circuit will comparatively be simple and economical as well. That's why I asked the previous question. I actually don't know my thinking is right or wrong! but I'm trying. you know MOC 3041 or MOC 3063 which has a built-in Z-C detector option. Besides that if it is possible then there is another problem that is how to connect MOC3041 with u-Controller. I will be very grateful to you if you assist me regarding the above two projects (1st one is quite difficult but I think that is possible) particularly send an email to me (my email is rashed_3e47@yahoo.com) so that I can discuss everything in detail with you about the two projects. Thanks again for replying to me despite your busy schedule.
You've got quite an interesting project there, and I'm tempted to get involved. But please understand that this is just a hobby for me, and between my real job and my spouse I've unfortunately got not time left to work with you on your project. I hope that's not too great of a disappointment to you, but I really don't want to commit to something that I'm unable to go through with.
I learned so much from this video! I like your style!
You're welcome! And thanks for the praise :-)
Thanks for the excellent video. To detect zero-crossing signal by a microcontroller, generally, we use a rectifier then a 4n25 optocoupler, and then a microcontroller. by these detected microcontroller zero-crossing input signal then we use MOC 3021optocoupler/Triac driver to trigger Triac BR136 from the output signal of that microcontroller. My question is Will you tell/Teach us, Mr. Robert's Smorgasbord, that if we use the MOC3041/moc3063 Zero cross Triac driver then can we avoid the above-mentioned arrangement and implement only by a MOC3041(or moc3063) with a Microcontroller to drive an ac load like a ceiling fan.
Thanks for the praise! And thank you for the excellent info! To answer your question: If you just want a simple on/off solution, then yes. That's what I was aiming here for. The zero cross switching here is simply for noise avoidance. If you need phase control, e.g. regulate the speed of the ceiling fan, then no. Though you could implement some speed control by switching on for single half waves.
Great man!!! This is the video what I need. I almost watched every video on yt but still confused. Thanks man. Good job.
You're welcome! And thanks for the praise!
Great Video, very detailed and easy to follow. I have an application running off a 24VAC generated by a mains powered transformer, therefore already isolated. What will be the risk of driving the TRIACs directly from the uC (supplied by a rectified 24VAC) without isolation from the 24VAC itself? Thanks!
The risk would be that the pin of your uC is exposed to 24VAC through the gate of the TRIAC :-) No, seriously, it's possible. If the power supply of your uC is galvanically isolated from the 24VAC - no problem at all. If you use the same 24VAC to power for the uC you need to make sure in your circuit design, that the aforementioned 24VAC can't get to your uC. Here's an example circuit that does that with AC mains: www-user.tu-chemnitz.de/~heha/Mikrocontroller/Triac8/index.en.htm
... a well pump of 1000w which has a start winding and run winding. Problem is, inrush current is larger than the 5kw inverter can handle. Solar installers recommend a large inverter of 10kW to be able to handle the inrush current which I think is an overkill for inrush current of a few milli seconds. Which is the best way to go to limit the inrush current? Ntc thermistor may also be an option, but repeat start within the cooling off period of the ntc of about 2 minutes will cause another large inrush current. Not sure if ssr zero crossing can be used to switch on/off an inductive load such as a borehole pump.
First, of course you can use zero crossing to switch a borehole pump. But it will not necessarily reduce the total inrush current (just the spike when you switch on with the AC at its maximum voltage). Would it be feasible to "forbid" switching on the pump within 2 minutes after shut off with a little circuit, so the NTC can cool down? If NTCs are not an option, you'll might consider a variable frequency drive that slowly ramps up the RPM. It will set you back a few hundred bucks, but that's still cheaper than a 10kW inverter.
Vielen Dank für die detaillierte Einführung.
Nichts zu danken!
Hi Robert, further to my previous comment, I was wondering whether you would give some thought to do a similar video on a DIY "SPDT" solid state relay (automatic changeover switch), using Triacs and Optocouplers? We regularly have power cuts in a very warm South Africa and rely quite heavily on Solar Power, i.e. constantly switching between an Inverter and the Mains Power Grid (230v) to keep fridges, etc. running. Thanks again for your excellent videos.
I'll put it on my wall of video ideas. But no promises though. And I thank you for the praise!
Thanks for the awesome video. I really liked you went through all the calculations, I learned a lot. Can this approach also be used to trimmer the resistive AC load with a PWM signal from the MCU or I need to use a phase control circuit? Many thanks in advance
Since the method shown here always switches full half waves, the frequency of your PWM signal needs to be much smaller than your AC frequency. E.g. a 5Hz PWM signal could modulate between 0 and 20 AC halfwaves passing through for a 50Hz AC. If your thinking Arduino, you will have to program such a PWM manually (lots of statements with millis() and micros() 😅).
excellent video - thanks a lot !! I really needed this to create a triac driver for an espresso machine boiler ... exactly 1.5kW, so, I did steal some of the math directly
You're welcome and thanks for the praise! And feel free to steal as much of the math as you want 😅
Hi, great video, I learned a lot doing the calculations. I'm using a moc3041 and a BT136 and I can see that using a different Triac the gate current would be smaller. I have one question which I hope you can answer. Using your circuit, my Hot lead 230vac live is connected to T2, and T1 goes to the load. WITHOUT switching ON the opto-coupler, can I connect a live to T1? WHY I hear you ask, well the opto-coupler circuit is to switch on my heating boiler when the temperature falls below 5degs (a Frost stat) where normally the load is controlled by the timer and temperature setting. So T1 would get it's power when the Gate of the Triac switches on, and also from the household timer.
If I understand you correctly, you're basically shorting out the TRIAC via the timer/temperature switch. Or in other words, you have the TRIAC and the timer/temperature switch in parallel. And yes, you can do that :-)
@@robertssmorgasbord Many thanks, I'll give it a go. I have used a relay to operate it but needed to replace it with a triac.
@@Richard-ul2sh You're welcome!
its commercial product ?
Thanks, I am about to make a video tutorial on PID temperature control of AC heating element via BTA41 triac. Your video helped a lot.
You're welcome! And please let me know when you've published that tutorial, 'cause I'm currently working on the temperature control of my laboratory water bath ( th-cam.com/video/UHtsRI7svAk/w-d-xo.html ).
Hi, excellent video, I have a couple doubts , Is there any way to measure the sine wave without the isolation transformer? how can I measure the trigger wave from the microcontroller and the AC wave. Regards
First, thank you for the praise! There is a error prone and very dangerous way to measure the sine wave with an earthed oscilloscope without an isolation transformer: Connect your oscilloscope probe ground to mains AC neutral. Make absolutely sure it's connected to mains AC neutral! Make also sure that there is no significant voltage between mains AC neutral and earth in your mains AC installation! Disclaimer: This is not a recommended procedure and if carried out incorrectly can damage your equipment, cause injury and death!
I don't think it's possible to measure the signal from the microcontroller and mains AC at the same time with a single oscilloscope without the use of additional isolation equipment (isolated probe, isolation transformer etc.).
Really awesome, thank you. I wonder why an opto-triac must be used in conjunction with another triac for AC switching? Is it because of the limited on-state main-terminal current of the opto-triac?
Thanks for the praise! And you're welcome! Anyway, the answer is yes: The MOC3063 can dissipate at most 150mW and has a maximum on state voltage of 3V. Meaning 150mV/3V = 50mA(effective) is about the maximum that thing can handle continuously. For my 230V AC that's 230V(effective) * 50mA(effective) = 11.5W. That might be enough to switch an LED lightbulb, but not enough for my application.
Would it make a difference if we used 2 parallel 800 ohm resistors instead of 2 series-connected 200 ohm resistors? In series connection, the voltage rating on the resistor is lower. So would it be better connected in series? (And It was a exactly great video, thanks!)
Not really, as long as those 800 Ohm resistors are rated 250Veff AC (in parallel the total voltage rating is that of a single resistor). The only reason I'm using two 200 Ohm resistors in series is to get with cheap 1/4W resistors a voltage rating of 250Veff AC (yes, in series the voltage ratings of resistors of the same value add up). You could also just use a single 400 Ohm resistor that has a voltage rating of 250Veff AC.
Hi, very nice explanations.
I am designing a circuit to control roller shutters using Arduino (or ESP8266, not sure yet). So a 5V or 3.3V circuit.
So for 3.3V, Rled will be 240R and for 5V, Rled will be 430R.
As it is an inductive load (but with a power factor >0.95 as stated in the datasheet of the motor), I will use a BTA16-600BW (snuberless) as triac with a very small heatsink.
I will add a resistor between the gate and M1 as suggested in your video. Do you think that 330R is OK?
The motor is controlled by 2 phases (up and down). Of course, they must not be on the motor at the same time.
I will first turn off one phase before turning on the second phase. the triac will turn off at exactly zero crossing, BUT the other triac might turn on before the first is off as seen on your oscilloscope.
I can then wait more than 10ms before turning on the triac after turning off the first triac. But is it a hardware way (interlock) to prevent the turning on of one phase if the other is not off yet?
Thank you
The peak gate current of the BTA16-600BW is 4A. So at 230 V (peak voltage +10% 358 V) you should be fine with 330 Ohm (aboutish 1 A).
You could use some external logic chips to implement a hardware interlock. The logic functions would be:
1. optocoupler: [mcu 1. optocoupler pin] AND NOT [mcu 2. optocoupler pin]
2. optocoupler: [mcu 2. optocoupler pin] AND NOT [mcu 1. optocoupler pin]
So you would need two inverters and two AND gates (the outputs of the AND gates driving the optocouplers of course).
I do enjoy your deep dive stuff like this very much, but I no youtubers don't like " requests" so this is a "if you fancy it and get a moment" semi request thingy, I would like you to explain ADC's, maybe with the popular cheap module ADS1115, at the moment I'm interested in measuring small voltages and currents. Perhaps you already had this in mind or simply don't like the idea but please keep your explanations and tutorials coming they are much appreciated by me and many others...cheers.
Hi andymouse123, I was already thinking about doing some ADC and DAC stuff. The reason being Arduinos lackluster 10 bit ADCs and its total lack of DACs - you don't always want to fiddle around with the PWMs. I can't promise that I'll use an ADS1115 or when exactly I come around doing that video, but it's definitely in the queue now.
@@robertssmorgasbordOh!...absolutely, that's great Sir...cheers.
@@andymouse Just ordered the ADS1115 modules from Banggood ;-) Though, it will be a while until they arrive.
@@robertssmorgasbord Oh, that's great! I look forward to that, im finding the subject very interesting, in fact the whole world of power supplies, test and measurement etc...cheers.
Hello Robert! Awesome and clear video. Can you explain your testing setup a little more? I am looking into analyzing some problems in my TRIAC circuit with an oscilloscope but have been running into warning on every single forum about measuring mains voltage with an oscilloscope.
Thank you!
Karim
Read manual of the osciloscope how to connecto AC, its definetely there. Something like swithing on probe to x10 divider and click auto-adjust on the osciloscope - and you should se the sine wave.
You can use transformer to work with safe voltage (< 30VAC), e.g. www.aliexpress.com/item/4000668357474.html or any other low AC transformer.
@@sindbadoo BNC connectors are connected to earth. It's not as simple as just put it on 10X. There are multiple safe ways to do it, two of which are using an isolation transformer (NOT ON THE OSCILLOSCOPE, rather on the device under test (DUT)), and the other using high voltage differential probes (still useful either way).
I'm asking about the particular setup Robert had. I see an isolation transformer (that APC), but that doesn't tell me how he setup the entire thing, which is what I'm interested in.
Hello Karim! I supply the TRIAC circuit from an isolation transformer (the big black box with the bluish display - see "Small Project: AC Mains Isolation Transformer from Two Broken UPSs" th-cam.com/video/SlTDqRNryuM/w-d-xo.html th-cam.com/video/SmCYR4FNrSs/w-d-xo.html - of course you can buy one) with 230V. So the 230V within the TRIAC circuit have no potential to / are isolated from mains AC earth. This way I can connect the ground of the oscilloscope probes, which are indeed connected to mains AC earth, anywhere in the circuit without causing a short from mains AC live to mains AC earth, which might destroy the circuit and the oscilloscope. And you're welcome!
Hi there. I loved the video. I like how you explained the circuit design so simplistically. I was wondering if you mind making a video on snubber circuit designs (specifically for random crossing opto-couplers) and possibly addressing the pros and cons of using a zero-crossing optocoupler verses a random phase optocoupler.
Hi Vutivi, I usually do these tutorials for stuff I actually plan to use in my projects. Currently I have no project coming up in need of switching an inductive load with a TRIAC, that is in need of a snubber network. Same holds true for switching TRIACs at random phase angles. However, as soon as I'll need these things there will be related tutorials - no promises though.
@@robertssmorgasbord Oh I understand. Thanks anyway.
I'm interested in seeing what your finally project is. All the best.
@@vutivimashele709 Thank you very much for your understanding.
Just to make an observation supporting this request: you put a tremendous work to cover the triac application area. I think the crown will be placed on your work if the very last part will be published: controlling inductive load by triacs. Unfortunately very few material can be found on the net about this topics comparing to the other application areas. Desiging the scrubbing on the optocoupler and the triac side seems an other science therefore your detailed explanation and presentation on this field would be valuable. Thank you for all the work you invested in this area and I hope one day you really need to control an AC motor.
Fantastic video! I know you made this a while ago, but if you have time would you please consider a supplementary video with information about implementing a snubber circuit for switching inductive loads? Thank you!
Thank you for the praise! Regarding inductive loads and snubber networks: I'll put it on my wall of video ideas - no promises though. But I do have one question: Do you want switch your inductive loads on zero-crossings only, or do you intend to implement some phase control?
@@robertssmorgasbord I want to switch 24VAC sprinkler solenoids. My first attempt used mechanical relays and had all kinds of electrical problems when they switched off. Then I added a snubber and those problems went away, but now that I've learned more I want to move to triacs (i.e. something without a mechnical switch). For my application, switching on zero-crossing seems to be the solution, but you pointed out in your video that the zero-crossing triac-output optocouplers don't necessarily switch at zero, and my load being inductive will feed some current back into the circuit. I'd like to learn how to properly implement a snubber on this kind of circuit with a triac. Thanks again!
@@BrianDoylePDX There are indeed cases where a zero-crossing triac-output optocoupler might switch on not at zero. But these are worse case scenarios (like the AC power is coming on at the peak of the sine wave). Of course you have to dimension your circuit for it (in the video the gate resistors), but I don't think with 24VAC solenoids it will cause any issues. There are also snubber-less triacs available (they can take the voltage peaks from an inductive load without uncontrolled retriggering) like the ST T435T-600FP (4A, datasheet specifically mentions switching valves ;-) ) or the BTA208X-1000B (8A). How much current do your solenoids draw?
Hi Robert. Great video.
Unfortunately, I still can't understand how you calculated the 80mW current across the current limiting resistor. More. Usually, there is another resistor between the gate and one of the anodes with a value similar to the value of Rg. What about its current and voltage specs?
Thanks in advance!
Thanks for the praise!
What step(s) exactly of the calculation for the power dissipation of RG ( th-cam.com/video/rLpFtSayZ3Q/w-d-xo.html ) is/are unclear to you?
The sometimes used additional resistor between the gate and T1 (never T2!) is only necessary in noisy environments (e.g. switching high power brushed motors). It "shorts" unwanted voltage/current spikes at the gate to T1 and thus prevents unwanted triggering of the Triac by noise.
@@robertssmorgasbord Thank you for your prompt reply. Actually, I can't understand from where you get tGT and the bottom value: 2us/10ms values. I use BTA12-600BW for my switch.
Thanks
@@NaudioElectronics Let's start with the 10ms. That's 1s / (50Hz * 2), or the time between trigger events if you want the TRIAC to be switched on all the time. For 60 Hz it would be 1s / (60Hz * 2) = 8.3ms.
t(GT) is the time the TRIAC needs to become conductive after being triggered, and thus the time current actually flows through the gate. And indeed, ST is not specifying that for the BTA12 in the datasheet 😞 But I'm sure if you use 2 0.25W resistors in series as I did, you'll be fine.
Hope that helped!
@@robertssmorgasbord Sir , what will be the value of additional resistor ?
@@NaudioElectronics Is BTA12-600Bw is better then BT139 ? any other much better option available ?
i loved the video ,you r an excellent teacher sir . thanks for ur work .
Thank you very much! I don't know about "excellent" :-) I'm just striving for correct and - if possible within the context of a video - complete information about a given subject.
Great video, thank you. I am interested in using ssr zero crossing to switch on a well pump(
Thanks and you're welcome! BTW perfect application (well pump) for a TRIAC switch.
very clear instruction, thank you !
You are welcome!
Hi nice video, I would like to measure the AC wave with my oscilloscope, could you tell me which APC equipment do you use?
The "APC" device shown in the video is actually not an an device from APC 🙂 It's an isolation transformer that I build from two defect APC uninterruptable power supplies (UPSs), reusing one of the enclosures and both of the transformers: th-cam.com/video/SlTDqRNryuM/w-d-xo.html , th-cam.com/video/SmCYR4FNrSs/w-d-xo.html . But any commercially available isolation transformer will do the job, probably even better😉
@@robertssmorgasbord ohhh i see, thank you very much for the clarification
@@hectorbarrera9496 You're welcome!
Great video. Should I use a zero crossing optocoupler or a zero crossing power triac or both? my waveform is very interesting I wish I could upload a picture of it.
Thanks! Well, if you find a zero crossing power Triac, and you don't need the galvanic isolation the optocoupler provides, then you could of course use that zero crossing power Triac. Please let me know the type of Triac you have in mind.
Thank you for the reply. My power triac is nothing special. It is a 600 volt 20 amp. It is random fire. Also, I do need the isolation so the optocoupler is definitely necessary. I obtained a few zero crossing triac optocouplers today and the sine wave is now extramely clean. The power triac is still random fire but it is impossible to tell. The zero crossing driver is correcting the zero crossing for the random fire power triac. The transition is perfect. Now I need to apply all of your math to ensure it will last. Awesome video. I learned a lot and will use what you have taught me frequently. Chris.
@@1southsoon You're welcome! And I'm glad that I could help.
Thank you too. Keep up the great work!
@@1southsoon Again, you're welcome! And I'll do my best to keep up the good work 😅
Great video. One thing that i can't undestand is when i created a PCB with this schematic but somehow switched triac terminals T2 and T1 then circuit was not working. Do you have any idea why this is happening? I though triac is biderectional. Also could you please make another video with calculation of the resistor between gate and T1? does it also affect the value of Rg resistor?
Thanks! While TRIACs work bidirectional in regards to T1 and T2 they are NOT symmetrical in regards to G and T1, respectively G and T2. The voltage at G is ALWAYS referenced to T1. In other words, the voltage between G and T2 doesn't matter when it comes to triggering the TRIAC. See also the links in the video description "TRIACs - The Dirty Details ...". So I fear you will have to make another PCB where you have T1 and T2 connected correctly. As for the value of Rg ... I went over the calculation of its value at 09:38 - what exactly is your question?
@@robertssmorgasbord thank you for the reply. I think i understand now. I will rework the PCB. For the resistor I did not mean the Rg resistor calculation but the one which puts t the gate down to prevent false triggering (not in your schematics). The resistor between the gate and T1.
@@Mikomanus You're welcome! Regarding your question, have a look at electronics.stackexchange.com/questions/248743/how-is-the-gate-trigger-resistor-value-calculated-for-a-triac . That resistor between G and T1 is usually not required (that's why I didn't use it). You might need it if your TRIAC triggers at very low currents and you are in a very noisy environment.
Can you explain in more detail the purpose of a resistor between A1 and G? I have a very similar circuit to the one in this video, VACrms = 120VAC, Rg = 360 Ohm, the load is inductive, and it includes a Rn = 360 Ohm resistor between A1 and G. I'm having issues with the Rn getting extremely hot!
The purpose of the resistor ("Rn") between the gate ("G") and the terminal 1 ("A1"? Did you mean "T1"?) is to conduct induced currents - or simply noise - away from the gate. Remember, the gate trigger voltage can range from just a few hundred millivolt to a little over a volt! So even small voltages induced through magnetic fields (e.g. large electric motors) or electromagnetic noise (e.g. arc welders) can cause the TRIAC to trigger, if they are strong enough to induce a current of a few milliamps for a few microseconds. In your case the "noise" would have to induces a current of 1.4mA through that resistor first before a typical gate trigger voltage of 500mV is reached (500mV/360Ohm).
Robert Smorgasbord, why does increasing or decreasing loads resistance value will change Triacs Or SCR "holding current" and Passing Current?How can you bias a triac or SCR using Negative Bias?
Sorry, but I don't quite understand your question. If you decrease the load resistor value, naturally the current through the Triac will increase (Ohm's law) and vice versa. As for the holding current: It doesn't change with the current through the Triac. It's just when the current through the Triac falls below the holding current, the Triac will stop conduction. That is the current goes to zero. As for negative bias: What exactly do you want to negatively bias? The gate? The main terminals? And what do you want to achive with that negative bias?
Some Triac can negative bias the main terminals but the gate is positive bias or the triacs main terminals are positive bias and the gate is negative bias. What are the difference between how the terminals and gate are biased?
What is setting or controlling the triacs holding current? why does a triac have a holding current and why doesn't an SCR have a holding current?
@@waynegram8907 Ah, now I get :-) The holding current of a Triac is purely determined by its silicon structure, that is the size/geometry of the different N- and P-layers. See also "TRIACs - The Dirty Details (1/3): Gating, Latching and Holding" th-cam.com/video/I69Fiy3IwBE/w-d-xo.html
And SCRs do have a holding current I(H) too ;-)
Great video! Ok here's a silly question :) What is the model of that isolation transformer? Keep up the good work.
Never mind, I just saw your video about this Frankenstein beast. Love it!
Glad you liked that video too 😀
Thanks! And I will do my best to keep the video coming.
Thanks you. That was all I needed.
You're welcome 🙂
Hi Robert, with a zero crossing opto, if we switch an AC synchronous motor on the neutral side (Phase--->Motor---->Triac---->Neutral) , is there a way to figure out which quadrant the triac is operating at ? I am using 2 uC pins to drive a synch. motor in forward and reverse direction with 2xBT136 and MOC3041M.As you might have guessed, I am facing a lot of triac failures :( . An appnote I was reading "Thyristor and Triacs Ten Golden Rules " mentions avoiding triggering in 3+ quadrant (MT2-,G+) as one of the golden rules.
Figuring out in which quadrants your TRIAC is working shouldn't be a problem. But I need to know a little more about the circuit: Is the TRIACS T1 connected to neutral or to the motor? Respectively, is the TRIACS T2 connected to the motor or neutral? Where is the 2nd pin of the optocoupler connected (assuming the first one goes via a resistor to the gate of the TRIAC) - between the motor and the TRIAC, directly to phase or directly to neural?
@@robertssmorgasbord Hi Robert, Thanks for your reply. MT1 is connected to Motor, MT2 is connected to Neutral. Pin 4 of the Opto goes directly to Gate (no resistor). Pin 6 of Opto goes to MT2 (Neutral) through a 470E resistor. There is a 470E resistor directly across the Gate and MT1.
@@mumbaiverve2307 Looks good, your triggering with MT2+/G+ and MT2-/G-. Questions: How big is you synchronous motor? Do you have you an RC snubber network in place (motors are inductive loads!)? Is the heatsink for your TRIAC large enough?
@@robertssmorgasbord Hi again , the motor is very small , 0.003HP (125mA). It can rotate in both directions. Hence there are 2 ZC Opto/ Triac combination triggered from 2 uC pins. There is a RC network on the motor, I dont know if it does only snubbing or also meant to create a phase difference for the motor to rotate (like Capacitor on fans). There is no snubber network on the PCB across the MT1/MT2,though.
Just an addon query :Is there any benefit to trigger the gate at a positive going or negative going half cycle ?
Fantastic video, subscribed!
Thank you very much 🙂
Hi, silly question, for the probes where the gnd must be connected? I can connecto between T2 and T1?
Again, no such thing as a silly question 😉 In that video I connected the oscilloscope probes just across the load (see red arrows here: th-cam.com/video/rLpFtSayZ3Q/w-d-xo.htmlsi=H_jZpEFONajM_lWA&t=1988 ). It doesn't matter which way around, since we're measuring AC. WARNING: You're oscilloscope ground is usually connected to the AC mains ground. So without galvanically isolation your circuit (I'm using a transformer here), you might create a short and create a big bang!
you said you can use mosfet. how should i do that?
Have a look at that: electronics.stackexchange.com/questions/369187/how-to-switch-ac-using-fets
There's also a link to a TI application note there.
Hi,
I have an electronic board to control an AC motor -2500 watts/220v.
On the board are mounted two TRIAC - BTB24-600BW . The motor has a problem-runing on reverse only-no matter which button is pressed-FW or RW.
I found that the resistor who is connected to the Gate terminal on TRIAC 1 is burned and I replaced with a new one 47 Ohm/1 w .
Also I found a short cut between the Gate and Terminal 2 (the midle terminal) on the same TRIAC and replace it with new TRIAC--BTB24-600BW.After that I did a check by multimeter between all soldering points.
Then the board was connected to the motor.Unfortunatly the motor not run-in any directions- clock wise or reverse !
Do You can to gave me any advice?
Well, without knowing the whole circuit and the type of the AC motor (I'm assuming it's a single phase universal AC motor) it's quite hard to give some advice. For example: Are your sure the burned out gate resistor was 47 Ohm? Because that would give you a peak gate current of 220V*1.41/47Ohm = 6.6A, while the BTB24 is only rated for 4A peak gate current. Also, how does the FW/RW button/circuit work? Anyway, if you desolder the BTB24 again and just solder in a (reasonable thick) wire between terminal 1 and terminal 2, then the motor should run at full speed as soon as you connect the circuit to AC mains. If that's not the case, than something else beyond the TRIAC has been damaged.
Any thoughts on using a triac to swich on a 2 rpm swing motor used in air conditioner units instead of electromagnetic relay?
Sorry for the late answer. I don't know what kind of swing motor you have in your air conditioner. But normally those are relatively low powered synchronous AC mains motors (two wires) or low voltage DC stepper motors (at least four) wires. The latter you obviously can't switch with an TRIAC. But since you mentioned a relay I guess it's the former. And that you can switch with a Triac without any problems - AC is AC, whatever the load is. However, since it's an inductive load (motor coils) you might need to add a snubber network (resistor and capacitor) to my circuit, as it is shown in this article (figure 3): www.nutsvolts.com/magazine/article/triac_principles_and_circuits_part_1
how to calculate values of R and C for snupper circuit across triac ?
Well, unfortunately there's not a short answer. Have a look at that application note (18 pages): www.st.com/resource/en/application_note/cd00004096-rc-snubber-circuit-design-for-triacs-stmicroelectronics.pdf
Quick question. Can the load be connected on the T2 line instead of the T1 line?
Does this make a difference?
Yes, it is possible, and yes, it makes a difference. Please note that in this case the TRIAC-optocoupler also has to be AFTER the load, otherwise you'll get excessive gate currents. Regarding the differences see that thread on the ST Microelectronics forum: community.st.com/t5/power-management/which-pin-should-drive-triac-load/td-p/290881 (NOTE: The drawing posted there by the user asking the question is wrong! T1 and T2 are swapped in that drawing.)
@@robertssmorgasbord Thanks for your reply. Right now I have my load on the MT1 line. I have built a PID oven controller and it is working well. But still in development.
I asked about this because I have read that the load should be on the MT2 side but all the example circuits, including yours are on the MT1 side.
So if I put the load on the MT2 side the pin for the MOC3023 opto should be between the load and the MT2 connection? NOT before the load.
Is that correct?
I'll probably just leave it as it is because it's working but it would be good to know.
Cheers
Matt
@@TYGAMatt Yes, if you connect the load to MT2, then one pin of the optocoupler needs to be connected between the load and MT2. The reason being, if the TRIAC is triggered, the voltage drop across the load will limit the current through the optocoupler, the gate resistor and the gate.
I have to ask, where did you read that the load should be on the MT2 side? There are no advantages to that, only drawbacks.
You calculated resistor power to be 80mW. So why not just use one 390R 0.25W resistor? Why use two 0.25W 200R? Isn't one 0.25W still a lot bigger than 80mW?
0.25W resistor are usually rated for up to 350V. But the maximum peak voltage on European AC mains is (230V + 10%) * sqrt(2) = 358V. So it's better to use two of those 0.25W resistors in series (when they have equal values the rated voltage is then 350V * 2 = 700V) to be on the safe side.
Liked , Subscribed and simply awesome ...!!!
Thanks a lot for the praise :-)
What about to implement an external zero crossing detector?
You can absolutely do that, but what's the point (unless you want to implement phase control).
what about inductive loads? should I use Zero crossing or not to drive a contactor?
Switching inductive loads on is not problem. You don't need necessarily zero crossing to avoid noise when doing that to do that (though it doesn't hurt), the inductor itself will limit the switch on current. Switching an inductive loads off without causing noise/spikes is the problem, and zero crossing doesn't help with that. Usually a RC snubber network is added when handling inductive loads to ensure the TRIAC really switches off and voltage spikes are absorbed.
12:37 how to tell that I have to use 2watts resistor? why not 1 watt or a higher value. Is there a formula for these?
If you put resistors with the same value (resistance) and the same voltage rating in series, than you can add their voltage ratings together as the combined voltage rating. I only mentioned the single 2W resistor, because 2W types were the only ones I could find with a voltage rating above 358V. I ended up using two 0.25W resistors with a voltage rating of 200V in series, because combined they have a voltage rating of 400V. Besides, I calculated the power loss as 80mV, so using a 2W resistor seemed a bit wasteful.
@ 13:17 I really wonder how did you get a 358 Ohms resistor value? because 358V divided by 2 is 179 Ohms. its not clear even how did you get 1 in case of other ideas, so 358V divided by 1 is 358 Ohms, Still don't understand how did you get 1 there.
The 1A is the current maximum of the optocoupler ;-) Since it's in series with the Triac's gate, the maximum current is the minimum (1A) of what the optocoupler (1A) or the Triac's gate (2A) can take.
@@robertssmorgasbord Still confusing indeed. can you tell me the value of the gate resistor for this triac (BTA41-600BRG) with the same optocoupler you are using?
@@MicrosiMe The BTA41 can take according to the datasheet a peak gate current I(GM) of 8A, which doesn't matter, because the peak repetitive surge current I(TSM) of the MOC3036 optocoupler is still just 1A. So the minimal gate resistor value, calculated for the 1A the optocoupler can take and 230V AC +10%, is still the same 358 Ohm. The optocoupler simply can't provide more gate current to the Triac.
Anyway, if you're want to use a BTA41 you might wanna think about using an optocoupler that has a higher peak repetitive surge current I(TSM). The reason being that the BTA41 needs a whopping 50mA to trigger (maximum gate trigger current I(GT) quadrants I to III). The BT139 needs just 10mA there. So with the same gate resistor the BTA41 will trigger considerable later than the BT139 after the zero crossing of the AC voltage.
Hi, my question is... what happens if we interchange The Optocoupler pins with the track pins, that is pin4 going to gate and pin6 going to T2...?
In theory absolutely nothing. The output side of that optocoupler (pin 4 and 6) is an AC device after all. The polarity at its pins changes with 50Hz/60Hz anyway. If you had a very close look with an oscilloscope you might see some subtle changes, since the TRIAC / zero crossing circuit within the optocoupler would be operating in different quadrants. But we're talking very small changes in the timing.
@@robertssmorgasbord that's a great answer... Perfect understood
Thanks Robert 😊
@@sujatabargur You're very welcome 😃
how can I make a real zcv with less losses possible to 7500w resistive load
With the TRIAC you've got a voltage drop of about 1.3V. Assuming you run your load at 230V AC your RMS current is 7500W / 230V = 32.6A. So your power loss would be 1.3V * 32.6A = 42.4W. Please note that the power loss in a TRIAC scales linearly with the current.
With MOSFETs (see e2e.ti.com/blogs_/b/industrial_strength/archive/2016/07/26/a-modern-approach-to-solid-state-relay-design ) your power loss scales with the square of the current: P = I^2 * R. R being the on resistance of the MOSFETs. To have the same power loss as with the TRIAC solution we need R = P / I^2, 42.4W / 32.6A^2 = 40mOhm. And that's for both MOSFETs. So a single MOSFET would need to have a on resistance of 20mOhm. You can get those, but they are expensive (e.g. IPZ65R019C7XKSA1 $20 19mOhm). If you want to half the power loss compared to the TRIAC you could use UF3SC065007K4S $64 9mOhm. You can't get better than that.
So in your application I would go with the TRIAC as shown in the video. But of course you could spent $130 for MOSFETs and half the power loss.
@@robertssmorgasbord but these losses have something to do with zcd? because I saw others project that looks try a real zcv. using mcu calculation th-cam.com/video/P6mbBJDIvxI/w-d-xo.html.
the losses in the tric is just the current x volt of 2diode? like 1.3V x 32A? Or have to do with the cvd pf the optocouplers?
my Idea is control a electric shower 7500w and 220v. and I want all cheap parts and less losses possible. I was thinking in moc triac, lm35, pic 16f877,
@@ronaldo0grande No, these losses have absolutely nothing to do with zero cross detection (switching). These are the losses for the TRIAC / MOSFETs fully on for each full half wave. And yes, the losses in the TRIAC are just current x voltage drop over the TRIAC (approximately 2 diodes) - for the TRIAC being on for each full half wave. The zero scross switching is really just there to avoid noise. So your cheap solution will be absolutely fine. If you want to control the power your microprocessor can switch the TRIAC on for defined intervals. Say from 20ms on / 80ms of (20% power) to 100ms on / 0ms off (100% power) - basically a pulse width modulation. Please note that the on time should be larger that 10ms for 50Hz AC, otherwise there's a chance you miss the cero crossing for switching on completely.
cool, it was a master class
Thanks for the praise!
Can 2 or more SCR be connected in parallel to feed higher load
Paralleling TRIACs or SCRs is a really bad idea. One will trigger first. So the others will not trigger at all, being basically shorted out by the one that triggered first.
Thanks for reply, we need a replacement for BT136 with higher amps capacity (we need to drive 1.0 kW AC motor) which would you suggest.
I see tutorial of making soft starter using triac that arrange pararel, this is the link th-cam.com/video/s7dKrFWPC10/w-d-xo.html, is it work to make triac bt139 parrael like that video, or it only one triac that work like you said. The video maker said that it will multiply the ampere of the triac. Is it true?
This sheet is same for every where use for optocoupler ...?
Sorry, but I don't understand the question? Which sheet are you talking about? The datasheet of the optocoupler? My schematics?
@@robertssmorgasbord datasheet of optocoupler
@@HITESHTHAKOR-js2dh The datasheet of the optocoupler ( optoelectronics.liteon.com/upload/download/DS70-2001-026/MOC306X%20series%20Mar19.PDF ) is of course valid for every use of that optocoupler, not only for its use in conjunction with a TRIAC. Other optocouplers have of course their own datasheets and different specifications. Hope that answers your question.
Is it okay to switch, optocoupler no 4 to gate, and no 6 to T2?
Yes. The TRIAC side of the optocoupler is - like a TRIAC - an AC device. It doesn't care which side around it's put into the circuit.
Hi! can i replace it for the relay? If load 10a, what should I change? thank
Yes you can. The BT139-800E can handle the 10A. You just have to roughly double the size of the heatsink, respectively choose a heatsink with roughly half the thermal resistance.
@@robertssmorgasbord thank your!
@@hdkaudioproject6319 You're welcome!
"More detail... well... basicaly bigger" hehehe
And bigger is better, isn't it 😉
😂😂She'll be right mate with 350v in Australia
I was always under the impression that Australia uses 230Veff too. But now I'm confronted with you telling me ... That's not a mains AC voltage, THAT'S A MAINS AC VOLTAGE 😅
@@robertssmorgasbord It was just a bit funny you way said it. It was a good video though. We are supposed to have 230v but it’s usually 240vac often up at 250vac in practice.
@@SparkyJames Here in Europe mains AC is nominally 230V +/- 23V (10%). So we're also seeing voltages up to 252V. Both, the circuit and the TRIAC can take that - so they're save for Australia 😅 And thank you for the praise!
Unfortunately, you failed to show a varying input logic signal and how that affects the power switched to the load. This is how these devices are used in real world application ... sometimes as a 'relay' but more often as a time-gated power controller.
The title of the video does contain the phrase "Zero Crossing Triac Output Optocouplers". I'm assuming with "time-gated power controller" you are referring to phase control. A zero crossing TRIAC output optocoupler is generally used to avoid switching during the positive or negative phase (which would be phase control). That in turn avoids current spikes and switching noise. If you want to see phase control have a look at "TRIACs - The Dirty Details (3/3): Practical Considerations" th-cam.com/video/jjTr7DD2ouE/w-d-xo.html .