Over/under voltage detector - with schematic
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- เผยแพร่เมื่อ 19 ม.ค. 2021
- This is an odd device. It attaches to the side of a compatible circuit breaker, and connects to its outgoing connections. If an overvoltage or undervoltage situation occurs the device triggers and switches off the circuit breaker.
It's important to note that the unit musn't be powered continuously in a fault condition. If the power is not cut to it when it triggers, then the coil and circuitry will potentially suffer damage.
I took a guess at what the circuitry might be inside, but was completely wrong. In the true style of cost driven engineering, the circuitry is the cheapest possible.
If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:-
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This also keeps the channel independent of TH-cam's advertising algorithms allowing it to be a bit more dangerous and naughty. - วิทยาศาสตร์และเทคโนโลยี
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This tear-down inspired me to create a specialized safety circuit for our observatory. The gearboxes have (from 1971) quite-well-built German "tacho-generators" on them. These generators were used as part of the servo control loop back in the day, and they produce a well-defined output voltage based on their speed. I wanted to re-purpose one to use as an independent "trip" for the brakes and motor power if the detected speed on the axis exceeded certain bounds. I used something similar to what you showed here in your video. The main hazard we're trying to control is the elevation axis "running away" under gravity--that can happen if the control system has disabled the brakes, but is not driving the motor, or there's a break in the drive-train between the motor and the gearbox. This "tacho-trip" circuit will handily provide for a safety-trip in that situation.
Something to remember is that for undervoltage detection, it needs to not trip near the AC zero-crossings, hence the cap across the PNP transistor.
That’s a good point
And you need to negate the "race condition" on inital turn on, where the LV trip could trip before the internal voltage rails have charged to their nominal values etc!
Considering the mechanical nature of the tripping mechanism, and the fact that it's up to the circuit breaker next to it to cut the power, I wonder if this device can really avoid cutting the power near the zero crossing.
@@Retep4565 The cap on the gate makes it wait.
@@paulvandergroen9569 I was referring to the mechanical parts.
...... Clive's expertise extends far beyond any electrician I've met.
I've said it before, and I'll say it again. I don't care what INTERPOL say,
This man is a Gentleman, a Scholar, and a Top Bloke !
Prior to opening, Clive accused the Chinese manufacturer of having some semblance of complexity. Upon opening, he needn't have worried.
Really appreciate your videos 😊 I really love the accent and you're in Glasgow!! It's awesome!!
My mom is a MacKay from New Glasgow, Nova Scotia, Canada. I have second and third cousins in Scotland. Mom's 92 and reminds me she's still Canadian everytime I contact her. Even though she has been living in the United States for over 65 years.
I'm also a Ham Radio hobbyist for over 20 years. US call sign KB1DIG. Did a little contract work with Raython Aerospace and the Department of Defense just after 9/11/2001.. Production Controller for the retrofit of avionics on the KC-135 stratotanker.. Air Force version of the Boeing 707.. Flying gas can..
Played around with UHF VHF antenna design. Halos and collinear design antennas. Some of my stuff is still floating around on Google.
I'm retired to the Philippines 4 years now. Have been doing a lot of TH-cam videos. Mostly custom built ideas for motorcycle related stuff here in the Philippines. Plus some of the local happenings here.
Thank you for your work and best regards for your future from the Philippines 🤠
In the world of haphazardly using microcontrollers for most problems, it's nice to see some analog circuitry for a change. That being said I thought it would be more akin to Clives guess, kudos to whoever came up with that circuit
At work, we have Over/Under voltage RELAYS used in conjunction with PLC control for generator paralleling gear (utility/generator switchgear). We also have options installed in breakers (configurable for things like auto-charging/shunt trip etc.) with over-voltage and under-voltage triggers for the trip units. Typically, at least in our applications, brown-out situations are worse, so under-voltage scenarios are the main worry downstream.
I wish you were my instructor in school, Clive, as you're genuinely a great teacher and so calming to the ears.
It may also be used to trip mains breakers in the case of if you have a automatic backup generator. That way you don't try to feed the grid and endanger lives. Or break your generator
Most (all?) regional electricity companies will require a dedicated transfer switch to ensure you don't back-feed your generator onto the mains. A transfer switch will stop someone re-closing the mains while the generator is connected to the load which a simple UV on the mains will not.
I guessed the overvoltage part correctly - largely because I've use the same Zener technique for years. I was a little way out on the under-voltage as I had a two transistor system in mind, but quite like the elegance of this one.
Clive, you didn't get that circuit wrong, you merely invented a better one...
;o|
thanks clive for getting me back into electronics . ive used a h961-u battery bank pcba , nice , charges on anything , ive discovered that if your battery holder is unknowingly series and not parallel like you thought ... 10 volt on the battery terminals kinda screws the charge regulation.... orederd the correct battery holders this time . thanks for getting back into electronics man , great show im learning alot .
Neat. The UPS I just set up had variable under/overvolt triggering, but I bet it does it with much fancier (read: microcontroller-based) circuits.
I really liked the way they basically put caps over every trigger to stop them bouncing and then another over the whole triggering thyristor just to be sure.
This would be handy. A voltage spike took out my coffee pot and my Wolfgang Puck pressure cooker. Both of the thermal fuses went. Got new ones from Amazon and they're fixed now.
Wish my rice cooker'd had a thermal fuse.
Someone left it plugged in overnight after emptying it. By morning it was cold, so it got washed and put away. Next time we went to use it - nothing. Although one corner of the switch surround was suspiciously melty . . ..
Luckily the wires inside were sleeved in fiberglass, so when the hot lead decided to play fuse and burnt itself up it _didn't_ contact the (steel) shell - that would have been rather exciting with wet hands! Also luckily, the wires were connected with standard 1/4" (6.3mm) spades crimped on the ends. 5 minutes later it worked perfectly again.
Since there is no smoothing on the DC side of the bridge rectifier, the voltage will drop to zero every 8/10ms (120/100Hz). Presumably the capacitor across the Base-Emitter is the only thing preventing the low voltage circuit triggering in this case.
The next, even cheaper, Chinese knock off of this device would contain a capacitive dropper, a diode, a coil, some resistors and a Padauk microcontroller.
I'm not sure they could get cheaper than this.
Oi! What about the LED to indicate it's ON?
Cheaper chineese one would just be a LED connected to a resistor and nothing else
Having an indicator LED is vital and a (Chinese) standard, 'cause without it we wouldn't know it's (a) Lethal (product)...
I duno, those microcontrollers are expensive, several cents per chip! The local Shenzhen vendor can get you the discrete components for a hundred to the cent, each.
Once you explained how it all works it really seems quite elegant.
I imagine designing a circuit like this feels similar to writing a really compact and efficient bit of code.... not that I'd know how either of those feel. 😐
Analog circuits are fascinating! Often so simple, yet really hard to design, it takes a lot of time until you can design them rather intuitive like coding is.
20 years ago programing at work I took out 12 a4 sides of code with a complicated loop. Man, I remember that feeling. No one will ever know but it flicked my switch that day
@@SwimBikeRunFastest Unrolling and cleaning up loops is its own reward.
I called those beautifully clean algorithms "computer poems."
At first I wondered about the colors on the schematic, but I've learned to trust and was rewarded.
Clive you are brilliant; your description and graphics very nicely explained something I would have little insight into were I to take it apart.
I would be more likely to run off with that coil for the magnet wire to do radio stuff with or make Joule Theives
A nice simple, elegant circuit... unless it doesn’t trip the circuit breaker! You must try this out and let us know what happens Clive! (I expect the coil will just fuse very quickly).
I've got such a device for my travel trailer, here they're called an EMS or Energy Management System. They also detect things like reversed live and neutral, missing ground, etc and won't connect the load if they detect them or will disconnect on under/over voltage. The number of RV parks and campgrounds with badly wired or badly overloaded service is pretty shocking. While they aren't cheap they are certainly cheaper than replacing an AC unit or God forbid having an electrical fire.
I'd be surprised if they bucked the trend by having _proper_ wiring and load calculation.
I did commercial [extra] low voltage for several years in 4 US states, and I can count the number of installations I saw that weren't outright death traps without even taking both shoes off. My favorite was the panel that had _burned through_ the neutral bus bar because some screws were loose.
It's always exciting to find the problem before you've even properly started diagnostics. Went to open the first panel cover and saw sparks. Poked it again - more sparks. At this point (a bit late) my brain engaged and the next time I poked was with a meter instead of a finger.
The breaker cabinet itself was live at 240V. The sparking came from the front panel being pushed into contact with the aforementioned unanchored neutral bus bar. I'm still not clear on how it actually came about because it was out of scope _and_ outside our license, but we LOTOd the feed to that panel, informed the store manager, and bailed so I could be _deeply concerned not hysterical thank you very much_ somewhere out of sight.
OK, I'm 3 minutes 50 seconds in and my guesstimate is going to be: It uses a coil to trigger the trip and the reason it is real low resistance is that coil is in parallel with a near short circuit to allow the breaker to be minimally involved in the system (Not use much power).
unrelated to the video, but I love how your website is designed. takes me back to my earliest days of exploring the internet.
If my math on the dividers is right, accounting for the 0.7V drop, that's a voltage range of about 180-260Vrms.
It would be interesting to see your calculations. I'm getting slightly different values.
Overvoltage:
24k/(470k+24k)=0.0486
12/0.0486=247 V
Things not taken into account:
1) Rectifier diode drop. (2*0.7 V, essentially negligible.)
2) SCR trip current/voltage needed.
3) My value is theoretically a peak value, which would put the corresponding RMS value faaar too low. But, the capacitors would also smooth out the voltage, so to some degree the voltage present at zener cathode would be closer to the RMS voltage.
Did you perhaps do the same calculation and added 12 V for the diode drop, or assumed trip voltage of the SCR?
Undervoltage:
80.1k/(1200k+80.1k)=0.0626
12/0.0626=192 V
Not taking into account in this case the E-B voltage drop, as well rectifier voltage drop.
My values, taken at face value, would pretty nicely fit with a product for the Chinese market setting the thresholds at 220 V +/- 12-13 % or +/- 27-28 V.
@@Gameboygenius Voltage at center point of OVP divider is roughly zener plus SCR gate = 12.7V. 12.7=X*24/494. X=261
Voltage at center point of UVP divider is roughly zener minus Vce of the PNP = 11.3V. 11.3=X*80/1280. X=181
This assumes gate trip current of SCR is near zero, so it's only an approximation.
Remember that the supply is unsmoothed full wave rectified, and also there's a capacitor across the 24k resistor. This capacitor will average the rectified and voltage divided waveform to around 64% of its peak, or a factor of 0.9 times the rms value. So this will in fact trigger at around 290Vrms if perfectly smoothed, but more realistically a lower voltage allowing for some ripple depending on the capacitor value. The capacitor was unmarked but it would need to be around 1µF to smooth enough to have a 280 Vrms trigger, which I think is the rated value marked on the front of the device.
I replaced a standard switch fused spur with an rcd version a while ago. Didn’t pay much attention to the way the old one came off because there were only 2 twin and earth cables, a 1.5 and a 2.5. On re energising it held for a few seconds then the bang it made was impressive. You’ve probably guessed it. The 1.5 was the feed and the 2.5 the load. Excellent videos thanks. It was a timeguard spur from Edmundsons.
I found one of those digital ones that you can actually reprogram the over- or under-voltage setpoints.
Handily it works on 230 as well as 115!
It also has a programmable overcurrent, but it's not really meant to be used as a full-on circuit breaker - even the manufacturer recommends coupling it with isolators and real circuit breakers.
It's rated for 63A branch, and is available in 80A branch. Since American branches are usually only about 15-20A, I grabbed the 63A model and will put it behind a 60A breaker.
With that amount of protection, with not so ideal mains, you have to go to the breaker box many times a day :D
I do like a spectacularly simple circuit. (In terms of components). Mind you my favourite is still a West German stereo valve radio that had very few valves that were used for several different things at the same time because radios were taxed by the number of valves in it.
I demand that that coil be connected across the mains in the case! It would be nice to see the failure mode, is it just going to quietly "fuse" out?
Thank you for the video :)
Vielen Dank für das sehr gute Video! Ein toller Kanal mit genau der richtigen "Erklärungstiefe".
I think part of the coolness of this design is the failure mode for the two 3 terminal devices. If either shorts the device will trip. The zeners are very lightly loaded so they are very unlikely to fail.
I have learned SO much watching you tear things to bits. Thanks!
I know this breaker is for over and under voltage protection, but I noticed that you mention the possibility the wires were for tripping the circuit. Over here (USA, I'm sure they have them there too) those are called shunt breakers. My public school system has a vocational school for high schoolers that has various trade classes (metalworking, HVAC, automotive, masonry, etc.) and in every shop, there were several red buttons placed around in different places. When the button was pressed, it would trip the shunt breaker powering the outlets and machines in the shop it was in, in case a kid was about to get their hand chopped off or other dangerous act that needed the electricity off.
Why do I keep watching these videos I don't understand a word of what this guy is talking about. Yet I keep watching him every time he comes up XD
Excellent analysis of a surprisingly clever and robust design. Most fault situations will result in firing the disco solenoid. And not a moderne window comparator in sight. Thanks!
Interesting item, excellent teardown and reverse engineering.
Great vlog thanks for sharing.
Best regards from the Black Country.
John.
Excellent video as usual. I like the idea of predicting what might be inside, then open it and see how they really did it. Very interesting and educational.
I did a DIY version with a SSR and a lm339 almost 10 years ago(I was going away for the weekend and the voltage had been fluctuating all week), you know the kind of temporary FOREVER circuits in a perfboard that since it's been working fine will never be disturbed.
Some day I'm probably going to put a uC maybe....
Clive pulls out the power tools again, at least its not explosive this time lol. Love the videos btw, reminds me of my childhood.
The device you talked about which trips after applying power (or after removing power, there are both types available), we use one of those at work to trip the main breaker in a small room (lighting is on a separate circuit) to use as an emergency stop for everything in the room, it's a simple additional safety device, you don't think what to turn off, you cut the power if something goes wrong
It always amazes me, how they can build cheap but funcional product :D
An elegant circuit to be fair.
I though wonder how consistent it is from unit to unit. Considering the tolerances of the components.
The other units seems quite interesting as well, could be useful to have if one lives in a brown out prone area.
Immensely interesting. Your explanations cannot be faulted.
Well Clive, videos just got another quality upgrade. Great idea and great vid as usual 😉
Really the circuit which is shown at 15:18 is a very simple one but very clever ingenious circuit. The circuit which is shown at 05:17 is also very clever and it is found in the 555 timer chip to generate the ramp function upper and lower limits where those two comparators set the memory to charge or discharge the RC timing network in the 555 timers. The logic of all engineering is so ingenious and the sequences should be introduced at schools including the logic of the bootstrap circuit and its connotation of someone lifting himself by pulling at his own bootstraps.
A very interesting and very simple wiring diagram. Great explanation!
Be great when using a generator powering a house during an outage. Non inverter types rev up and increase output when running out of fuel.
"I won't touch the leads because it'll interfere with it"
Ohhh boy, on a scissor lift a million miles in the air testing fuses for a 3 phase thing on a bus bar box with a fluke clamp meter (using the probes in continuity mode obviously)... All the fuses are fine... Wtf?
No, one is gone... The meter is faulty and its reading my body resistance from one hand to the other as continuity.
We kept the meter... Fantastic to give to someone to check fuses and to learn this lesson
Clive, that one relay you showed early in the video without the volt meter on it is an overcurrent trip relay. Obviously you would want a breaker or fuse upstream to trip in case of a short.
BTW one of your better, more relevant videos. A definite upvote!
Hey Clive would you consider making a playlist on your channel of all your uploads? I like listening to your videos at night falling asleep, but autoplay starts videos from other unwanted channels after a few of yours. If there was a playlist consisting of all your uploads I could be lulled to sleep by video after video of interesting electronic teardowns.
This would get tripped so often at my place, haha
Very clever little circuit.
thanks so much for your videos and the work going in to it. really apriciated and worth watching you videos.
You know, seeing the letters of that cathode, it makes me wonder if that was the original inspiration for the headphone company known as AKG.
You mean Samsung? XD
Like you my first thoughts were voltage comparator circuits using op-amps. I reckon that even this circuit could be cut down more at the cost of some reliability in use.
These are really handy i first came across one on an ebike it worked really well to stop power surges, cheers for the share :-)
The coil runs on AC (50/60 Hz) so the current won't be anywhere near 4 amps. An interesting circuit. Voltage thresholds are temperature dependent.
It depends on the inductance. As an open coil without anything on the outside I would think the inductance would be fairly low. I'd blindly guess 2 amps if run on AC.
220/60=3.6666666666666666667 A
Another issue pf
But it's for about few millisecond
~Fancy~ colors 💕
Great explanation, thanks....I liked your idea too !...cheers.
On low voltage detection it seems that the 12V Zener would be forward biased to limit the Gate Voltage. Clever!
Very interesting 🤔 Thanks for the video Clive. Enjoyed
Congrats on your newly secure workshop.
Interesting video, well explained!
When he suggested pausing the video I was already lost 😐
But did you watch the whole video? LOL...me too!!
Nice! Dodgy equipment again - thanx! That's what we need :) Keep it up please
BR Zlatko Jurkovac
Reminds me of three phase monitoring relays which are detecting phase order, overvoltage, undervoltage, missing phase and (if you buy correct one, for example HRN-57N) even missing N :)
Have to get the higher current rated one of those - might be very useful where we live "out in the sticks", where "mains" voltage can be somewhat variable! Any chance of an analysis of a mains spike / transient detector / counter? (another delight of a more rural lifestyle . . . . .)
Another fine video, and colors. Cheers from kansas.
"COIL" solder point on the upper left corner is confused
What would be good is a heat and smoke module. These are more for industrial where under and over voltage can really fuck up motors. But in domestic, it not really much use. But a module dedicated to cu and smokes makes great domestic sense.
very interesting circuit
Whether the auto-restart or permanent off is a better choice depends on the application. You certainly wouldn't want dangerous machinery to automatically restart after a brownout. Imagine someone getting close to said machine, trying to figure out why it stopped working and all of a sudden the power comes back... To be honest I can't think of a good application for an auto-restart after a brown-out from the top of my head...
Very satisfying video everseen
you said "20Megohm" like it's a dirty word
This would be good for sensitive vacuum tube equipment.
I was betting on something very discrety without any op amp or reference and I'm not disappointed
Also analogous is a 120V 15A power bar made by Furman with their EVS (extreme voltage shutdown), it automatically cuts out and back in depending on whether the voltage is in the proper range. I have no connection with the company, I just like the product.
That is such simple circuitry! Chinese are really ahead of their time.
didn’t see the livestream - did you test it with a variac to see if/how it worked?
No I didn't.
It seems the PNP transistor is always reverse-biased between E & B if it is not tripped by under-voltage. What will be the max reverse voltage just before the over-voltage part triggers the SCR ? Does the PNP Tr need a high B-E breakdown voltage ? Thanks.
My dad would take these out of the metrebox to take our power when we were kids and meant to be doing chores but would play N64 instead or watch TV lol
Same Idea as a Fire Alarm system that turns off the furnace (Kills Gas when Power is Disconnected from panel)
Had to install them at my work.
Any chance of demoing this on a variac. Both downstream and then upstream of the paired MCB. :).
Hi Clive. I noticed that the neutral lead is quite short (same length as the live) Are these only designed to trip double pole circuit breakers and RCDs? If you wanted to trip a standard MCB with it, would you have to extend that lead to reach the neutral bar?
It connects to the breaker it actuates.
Clive, do you use conventional current or electron current theory when you analyze circuits?
Conventional, since it's easier to explain operation when the diodes point in the right direction. The only time I reference electron flow is when dealing with MOSFETs.
Theories are just convenient ways to imagine how the universe works and predict it's behaviour. Use whichever Theory is most useful for any given task. So as Clive said that's mostly but not always conventional.
Clive CAD just got a color upgrade! :-D
Maybe I'm wrong, but since the relay coil is a purely inductive load controlled by alternating current, most of the power is purely reactive, it would not consume 220²V / 60Ω but much less
Can you do the video on other two devices? especially the 100amp one?
There’s a lot of 12v breakers I’ve seen , most are being used on solar power kits for camper vans , can you check a few out please Clive as one said 200 amp and tripped at 110 amps
Sir, could you provide a link where one can buy this devise..?
Didn’t know you were doing live streams.
Different channel - BigCliveLive
Ive seen these attached to motor circuit breakers, using the mcpbs switches to turn on/off a conveyor, this trips the mcpb when the conveyor is unplugged, stopping it from auto starting on powerup
Zero volt relay/switch.
Is your bench top Formica laminate or something else? THANKS. DH. INDANA
It's MDF.
I was hoping, you would test the limits with a variac.
Good stuff bud 🍍
Clive, What's the most important individual component in a circuit you've ever seen?
These days it has to be a microcontroller. But with discrete components, each has its own strengths. The MOSFET transistor has evolved spectacularly, so it gets special mention.
Are there any main breakers that self trip or switch off if there’s a power outage? For preventing islanding with inverters or a generator. Then you can have the inverter or whatever switch off when it detects voltage on the input side of mains, maybe a variant on the self resetting under over breaker that can work as a single space switch without needing to physically disconnect the inverter which can be connected passively through its own breaker
Zero volt relay? You set it, but if power fails it turns off and needs reset manually.
@@bigclivedotcom this sounds super not legit, but I guess things go different in 🇬🇧, if a relay could be used that would work so well because I could have a controller turn it back on when the prerequisites of power on one side and not on the other are met, or if they are able to take a standard slot and act as a breaker then I could have one for each, or just put them in an enclosure if that was up to code
Just found this video's thumbnail being used in an ad online "#1 way to cut electric bill!"
Yeah, stuff like that happens a lot.
So they have different models to fit different manufactures breakers or just for Chinesium breakers?
Won't work with Hager or Gyer from what I see.
It'll be deigned for a specific brand.
Could you do a teardown of a cheap UPS? I recently got one and I've been wanting to know what's inside...
Would this be suitable to recognise a PEN fault, I.e. losing netual and earth on a TNC-S system?
I think it would detect that. Plus brown outs.