Thank you for your support and attention to our company's products and thank you for your suggestions for improvement of our company's products. Our company's newly-listed FY6800 series signal generator will change the power supply plug to a three-core socket, which has solved the BNC leakage current problem.If FEELTECH products need to provide technical support, you can also send an email to feeltech@126.com and we will help you.
You made me curious, I've had mine for years and always had to earth the ground otherwise it would give me a jolt. So got up in the middle of the night, measured it: 2mA!
Yes! AWESOME! I'm a projects hobbyist who hasn't formally been trained in EE, basically I have a learning ethic and more than that, a natural tendency towards DIY! I have watched this particular video over a dozen times in 2016, as I had dedicated most of the year to the study of POWER SUPPLIES! I catch valuable info every time, just now I'm reminded to 'Check the dataSheets of your voltage regulators for drop out scenarios.', this stuff is just what I need, and it was by pure coincidence that I had just bought this exact function generator and by chance, happened upon your video. THIS VIDEO HAS BEEN A HUGE, VALUABLE SERVICE TO ME! Very encouraging. Thanks a lot!
I like the way you explain electronics.I'm an electronics technician and i have learned a lot from this video.Honestly, i never came across the floating voltage problem.Thanks for this great channel
Thank you so much for running those tests, very much appreciated. I was expecting some issues with the waveform but for the cost held up better then expected. A very nice conversion of the PSU to a more suitable format and can be done very reasonably with 'junk' parts.
Nice mod! I love modding my electronics, I mod pretty much anything I can get my hands on. I just finished modding a KVM switch, it used a 12v SMPS for power and a 5v buck converter for the 5v USB rails, I wasn't happy with this design as the buck converter could fail short circuit and blow all my USB devices attached (over £300 worth) So I made a very high quality 5v SMPS with 2 over-voltage protection circuits and bypassed the buck converter. :)
Found your channel linked on Banggood's page for this item. The best video I have found explaining the design of a power supply. Very well done! Thank you.
Hey. I just stumbled upon your channel as I searched for videos about LPS design projects, so this was my first experience of your video style. I'd say you have yourself a new subscriber! Awesome video.
I seem to be late to this party, but I just bought one of these (yes, they are still the same). Saw your previous video regarding the leakage and went searching for a suitable but cheap linear. I found a "SL Power Electronics Linear Power Supply MTLL-5W-A" on eBay for under $20 shipped and it seemed like it would fit (physically and electrically) so I ordered it the same day. The generator and supply both arrived yesterday. My AC leakage was lower than yours but at 43V, and 0,4mA, still a concern to me as it applies to connecting it sensitive equipment. The SL Power unit fits very nicely into the 3224 enclosure and is rated at about twice the currents needed by the 3224. Installation was a matter of a little soldering of longer AC power wires and moving DC power input wires to suitable pins and connector on the new supply. Works Great! Unit still floats relative to power ground (I wanted that) and the leakage is now under 6V and current 0.7uA
I attacked this another way. I left the switcher in place and put a 1:1 mains isolation transformer in front of it. Did you find that the fully linear supply made the output any cleaner?
Nice video! I like the mechanical layout and your test for a savety operation. It is allways wise to use a permanent load at the regulator output, because the stability and regulation gets greatly improved. This could be seen with a load change measurement.
Great tutorial, well appreciated by a novice in electronics such as myself. I also have this signal generator and have built your PSU solution using the same transformers purchased from Rapid Electronics, however I have a problem which because of my limited knowledge in electronics fault finding I am struggling to put right. My +5v and +12v are fine but I have no negative 12v output, just a load of random noise as viewed on the oscilloscope, and the dual 15v transformer is getting blisteringly hot at about 75 degrees C after about 5 minutes or so. I have my 5v rail on it's own heat sink and the 12v rails on their own much larger heat sink. None of the regulators are overheating and are sitting at about 25 degrees C, even as the transformer overheats. As I said earlier my lack of knowledge leaves me perplexed, I wouldn't even know how to interpret the oscilloscope output. I really love my electronics hobby and any help you could offer would be greatly appreciated. Thank's.
My plan (after installing a 317/337 linear supply) was to put an IEC connector on it and add a switch to enable or disable mains earth referencing. Looking forward to your USB isolation.
Thank you very much for this video. You are a very nice man to share your work and find a sollution for this product, and i think the chineze sellers will be happy too when there is a sollution for their product. Is nothing wrong with making and selling cheap products. I am a big fan from Banggood. I am just a hobbyist, i am not building a sattelite here, just try to repair an old radio or something.
Very nice job (and superb video production, as always). For the "DAC" one could look for the 8th-bit resistor and perhaps change it for one that more closely matches the other 7 bits.
A good looking project. I'm intending to do the same to mine. Well, similar. You've gone with two transformers and a fully linear design. I think for power considerations, what I'm intending to do is use a linear arrangement using 7812/7912 as yours for the +/-12V lines, but tap from the transformer down to a switching regulator (likely an LM2596) to generate the 5V line. Looking at the board arrangement, it only uses the 5V line for logic supply, but most of that is itself fed into the onboard 3.3V LDO, so I don't think it has to be that smooth. About the only thing the 5V line is used for directly is the LCD backlight - I'm sure that could put up with a bit of switching noise ;)
Yes, this sounds like a good plan. I realised afterwards that I still had an LM2576 which I could have used for the 5V rail, but the video hopefully served a purpose of showing how to design a linear supply. There's also an interesting alternative on the EEVblog forum using a pair of transformers to feed the existing power supply www.eevblog.com/forum/testgear/feeltech-fy3224s-24mhz-2-channel-dds-aw-function-signal-generator/325/
Useful to know this has so much leakage current, personally all this linear power supply and fan stuff is a sledge hammer to crack a nut, as the device will work down to 85v I would fit a cheap 240 volt to 110 volt isolating transformer in the case, remembering that this approach will only work for 240/220 volt supply unless the transformer is reversed 110 volt to 240/220
Great video, only it come little too late, if you did it earlier i would not need to have discussion with some "experts" and try to explain to them how voltage look after rectifier diodes and capacitors (by the way it was on your video #030).
I normally get accused of over engineering designs with huge safety margins but I think this has outdone even me. I would use a toroid (I always use toroids) with dual 15v outputs. A very small transformer. I would take the +5v off the 12v rail and use clip on heatsinks at about 8c per watt. First the 3watt will be dissipated across 3 devices. The hottest will be less than body temperature. Convection cooling with a couple of mesh covered holes at the bottom (near the front) and top rear panel will be more than adequate. The transformer will be stone cold. Also I assume this is at max output where the slew rate limits of the output op amps are going to wreck the waveform anyway. Most of the time it will be running an output of 3 or 5v p2p with correspondingly lower power requirements.
As an alternative how about battery power? Here is a multi output low voltage switcher with linear regulation of the outputs. www.banggood.com/DIY-USB-Boost-Single-Turn-Dual-Power-Module-Linear-Regulators-Multiple-Output-Power-Kit-p-1022517.html This gives +/- 5v, +/-12v and +3.3v at up to 300ma each. I have a couple of these for project breadboarding. I also have a couple of programmable loads so will soak a unit to check thermals. The lowest input voltage is 5v so a 6v supply with schottky diode protection can provide power direct and be tapped from the power module for the +/- 12v. An external 6v battery brick is no more inconvenient than a mains brick eliminating mains risks.
So using batteries along with that supply kit, would it also provide isolation of the generator outputs ? My alternative noob question would be to know if it's always better to have floating generators or if there are drawbacks you need to know abou, and would you recommend a simpler earthed PS and/or outputs mod for not so experienced users ?
Eldon Tyrell Most professional equipment has non-floating outputs. The only real issues this poses to a piece of equipment such as a signal generator is that the offset may not be adjustable enough for your purpose - say for example you wanted to use the generator to inject a signal to part of a circuit already at 20V relative to signal ground. Whether this is important to you depends on your circumstance.
I suggest to consider for the calculation of the capacitor (or 2° of the transformer), the supplied voltage of 210Vac (instead of 230) to compensate for the line voltage drops in rural areas or peak hours of absorption.
Hello, fine tweak you got here. Wondering WHY you have choosen 2 TRAFs w/2 separate bridges and ground instead of a SINGLE one derived from the MAIN 12+12 bridge w/ same ground. Any particular reason or just thinks it is better?
A couple of people have asked the same question I wanted to raise but can't find any answer from you. I was wondering why you didn't derive the necessary rails (+12v, -12v & 5V) from one dual secondary 12V transformer with 7812,7912 & 7805 regulators?. No heatsink (or very minimal heatsink on the 5V regulator fed by the 12V regulator) would then be required. Perhaps I'm missing something.
I would mod that panel to take the fused IEC connector, as the output sockets are going to be accessible metal in case of insulation failure on the transformer. Then connect the transformer cores only to mains earth. You could use a smaller heatsink though.
+SeanBZA The transformers are double insulated, so according to the IEC standard no earth is required even if there are accessible parts on the secondary of the transformer.
19:11 I had similar experience with LP2951ACMX/NOPB. It's output voltage is not steady and have dependance to input voltage and load. And datasheet says nothing about it. Or am I doing something wrong?
I know that it wouldbt be as elegant a solution but would just putting a small isolation transformer on the mains line before the stock power supply have also worked?
Nice work, but what is all the extra space for inside that case?. Why not make it as small as they can so it takes up as little space on the test bench as possible? It would be nice to have that space for other test equipment.
Hi! I´m a newbie ham, building my very first ham shack. I got an old oscilloscope for free from my father, which he himself once got for free from a physics lab when they upgraded. It´s a TeleQupment S54S, very old. I am looking for a rf signal generator and the Feeltech fy3200s fits my budget. I looked at your very nice vids on mods, but also noted you mentioning that other users have been reporting varying amp levels from the BNC connectors originating from the switching psu, which seem to vary regarding components chosen from unit to unit quite a bit., Is the leaking current usually as high as in the unit you have? I will be experimenting with the oscilloscope and a signal generator, learning the very basics of different uses and for antenna and feeding line testing for instance. I read some people suggesting bypassing the inboard psu and use a lab psu instead. Could I instead find a suitable wall wart from an electronics store and connect this to the pcboard power connectors? Is there such commercially available transformer based linear psu wall warts anymore? I´m probably not going to use the usb-port. Maybe I could find the same rf signal generator without the case and psu? Then again, is it possible that the manufacturer of the Feeltech 3200s by now has rectified the problem? It would seem that the Feeltech fy3200a is a good choice for a newbie with a low budget like me, but that current leak bothers me. So, I have a lot of questions on my mind, forgive my ignorance, but we all have to start from scratch as newbies....and forgive my bad English, I only speak Swedish and Finnish well. Loved your vids, learned a lot!
It would be really interesting to see if you could figure out a way to improve the signal quality at higher frequencies (and/or higher voltages). Perhaps some better opamps for the output, would solve part of it?
Hi if I connect the bnc of my high voltage floating Feeltech signal generator to a mains grounded bnc of my osciloscope always will this pose danger to my DUT or ground loop problems?
hola , perdón por preguntarte en otro idioma . Me interesa este generador pero tengo una duda - HAY ALGUNA DIFERENCIA ENTRE EL FY 3200S y FY3224S ?? los vendedores los ofrecen pero tengo dudas de cual comprar ,...gracias
My first thought was to simply use an actual isolation transformer (example: Triad Magnetics N-48X) and to retain the switch-mode power supply inside the unit. US $20 (with shipping) and running in a few minutes. Beef up the internal power leads in the process.
If anyone in interested, I purchased one of these from Banggood for $50. I isolated the AC input using a Triad Magnetics N-48X isolation transformer, and (as anticipated), the AC feed-through was removed. The transformer fits easily inside the case, and it mounts to studs on the case that were included by the manufacturer. Less that $70, total for a decent Arb (unneeded, since I have had an Arb on my bench for almost 20 years). OK, overkill.
Such isolation is important only if used with a PC that has is electrically connected to ground (many notebooks are isolated). However (IMO), it is not necessary to design an interface. This one from Banggood, which I purchased, works fine and is less than $9: www.banggood.com/High-speed-Isolation-USB-To-TTL-Serial-Module-Power-Isolation-Optocoupler-Isolation-p-1230932.html?rmmds=myorder&cur_warehouse=CN
Hi, i have a model of the previous series, the FY2200 that was sale in the 2,6,12Mhz versions, my is the cheaper, the 2Mhz, do you know if it possible to increase the maximum frequency ? It has the same altera chip and it looks very similar... Anyway great video!
Very nice job indeed. Just wondering are both terminals of the fuse holder shrouded/recessed/hidden on the outside? ie because either terminal could be live. Thanks for sharing.
Hi, yes, this fuse holder is quite nice - neither of the connections are accessible from the outside when the fuse is removed without poking something right into it.
I am buying parts to make the linear PS for the Function Generator...Will these transformers work? EI35 2W/2VA Power Transformer Input AC 220V 50Hz - Output AC Single/Dual 6V-24V I dont quite understand the 2VA rating. Thanks for your time.
Seems like a lot of trouble to go through. Why not simply use the two transformers to isolate the existing supply? Connect the two six volt windings together, and one primary to the mains, and the other to the supply input. Done!
Nice video! I have orderred the same unit from Banggood and looking forward to play with it...! I was wondering why did you not just modify the power connector to a grounded 3 wire connector so that the ground would be at zero? Would that not fix the issue of leakage that you find on this unit? Surely if the original ground is floating, bringing to a solit houseold ground would fix the problem in my view? Any comments?
Suppose you want the output signal to be relative to a signal level other than ground. E.g. a MOSFET gate with the source terminal hooked to 12V or 48V. Maybe you can do some of this using the offset, however power-up and -down remains a problem. If the signal generator output ground is tied to AC ground, it becomes harder to use and less flexible.
Are you using the right instrument to look at the output waveform? Your MSO1074 seems to have a bandwidth limit of 70MHz (despite the 1Gsps spec) which suggests you will not see an accurate waveform representation of the 24MHz output (3rd harmonic is 72MHz, yes? On the edge of your scope, perhaps?) Mind you, if you can see the distortion on this scope, it suggests it's probably much worse. But still... And was the monitored output correctly terminated?
Hi, the MSO has the 100MHz option enabled, but it's still possible. I put some more waveforms on my website from a high bandwidth Keysight scope 50R terminated.
Thanks for sharing this - I am planning to build something like this up myself. Might even get some PCBs done which would leave some over for others. Out of interest, do you have the various connector part numbers / series for the power connections?
The actual connectors used on the front PCB are JST XH series (the contacts are BXH-001T-P0.6, housings XHP-6 for the 6 pin versions). I used Molex KK connectors on my veroboard.
I had the same question and I think that is the safest way without building a power supply. Those direct mains power supplies can even be dangerous if bad things happen inside the unit. Never attempt to attach any test equipment (scope etc.) without an isolation transformer unless you are attempting to get burned, destroy the unit or commit suicide.
Hi Pedro, if you look at my earlier videos I have reviews of the LCR meter, the DCA and the ESR meter. I didn't get round to doing a review of the ZEN.
Instead of replacing the existing switching power supply by several linear PSPs, why don't you simply feed the function generator via a common 1:1 220V (ca. 50W) transformer?
Yes this is a valid solution, however I wanted rid of the SMPSU - it was a little noisy and has no place in a function generator. I also wanted this to be a basic tutorial for designing linear power supplies. Thanks for watching :)
SDG Electronic Yes, I see that now. It was late when I was watching. Do you have a drawing for the acrylic base you made that includes the dimensions for the holes etc? I just bought one of these for $65, couldn't pass it up. For my needs, I think this will work just fine.
+Adam Edelberg Probably nothing much as the -12 V feeds the opamps in the output stage. These are likely to consume more than 5 mA. And even if they didn't and the -12 V would become -15 V, if the opamps can handle -15 V then nothing would break. Besides that, LEDs rarely fail as long as you treat them properly. And at 6 mA, they should work for an eternity.
nice peter! in canada due the the 60hz i often find 4700uF caps in psu's im partial to 470-4700 @ 50V Negitive VR's require a negitive Rail. such as -12 as compared to a Plus voltage If you are going to do a 2nd part......Might i suggest adding a Vent Fan?
At 3:50 and so.... wouldn't it be a good idea to zero the clampmeter before taking a measurement? one can see, that it's floating around 30mA unconnected. quite a significant shift for the measurement.
Building a linear replacement for the switch mode PSU seems a bit OTT. Why not use 1:1 isolation transformer between mains switch and the switcher and keep the switcher? If you can't find a small 1:1 transformer use two 1:n transformers back to back. The VA is tiny so they will be smaller and cheaper than a linear replacement plus heatsink. Give the brain a rest and do it the easy way! You can buy USB isolating 'cables' if that is a real problem, but I doubt if I'd ever want to ever want to use the thing floating whilst driving it from a PC. In fact, the software is so incomprehensible I doubt I'd want to use it, ever!
@@sdgelectronics Thanks for doing this video. I'm a hobiest, and even after seeing your work, I bought this unit. It works well for my purposes. I'll be adding a simple isolation transformer.
I thought AC RMS value is 0.707 voltage of peak positive , how does the Negative RMS Voltage 0.707 get placed on the postive portion of the voltage? Nevermind as the power supply is a +12 and -12 output...so its 1.414...= Duh on my part.
+Jurva-Markus Vehasmaa I might investigate what is causing the issue. I suspect rather than adjust the reference voltage to the DAC, they just represent the sinewave with fewer numbers of bits, so it's probably a combination of the GBW product of the amplifier stage, or purely not enough resolution.
+Jurva-Markus Vehasmaa I guess you mean, low amplitude ? My guess is that there's no proper attenuator circuit after that R2R DAC (or an attenuator with a limited range) so the lower amplitudes are made by using only part of the DAC's bits. So at lower amplitudes the DAC would behave as 4 bit instead of 10 bit for example.
That heatsink is way overkill for the amount of power that those regulators are dissipating. And, vertical fins would get rid of the heat a lot better than horizontal ones. Also, the choice of small-value capacitor to put on the outputs of the regulators isn't as arbitrary as all that. The datasheets that I recall specify something like 1-10uF _tantalum_ or 25uF electrolytic. I'd be putting a smaller valued cap across there as well, say 100nF plastic film. The point is not only noise reduction but to keep those parts from oscillating.
$70.00 USD FY3224s, additional parts $60.00 ?? so $130.00 ish so basically around the cost of a Brand new Instek SFG-1003 or buy a used B&K Precision Model 4040A
+SDG Electronics , best I can see the 2 transformers alone are like £22 + £20 shipping. I'll wait until you post a parts list and prices like to see where your getting the £15 from, sounds like a great deal for parts.
+Martin P Hi Martin, the transformers are a lot cheaper than that - Rapid Electronics sell them for £4.30 each (e.g. Order Code: 88-3710), CPC also (order code TF01331). The regulators are around £0.50 and capacitors total less than £2. Then there is just perfboard and the heatsink. If you're in the US, I'm certain Digikey have similar.
Nice reverse engineering ,I hate switching supply with a vengeance they are engineered to save coper cost and are sold in modern equipment at the same cost as a good linear supply who have proven themselves to last for ever the only maintenance they need it's to change the capacitor every 20 years and go on for another 30 more years ,they are ton off vintage guitar and radio using tube with linear supply still working 60 years latter , and switching supply are really dangerous I had one in the digital display of our dishwasher turn off who took in fire in the middle of the knight the build in fuse never worked the PCB board of that switching supply burned a hole on the pcb really scary if we wouldn't have been there the whole house would have burned ! These switching supply have infected all of our modern electronic since the late 80 ,you can find some even in our LED lighting bulb replacement ! You just extended the life of this signal generator for 15 years if the rest of the chinese parts live to do their parts ..
Thank you for your support and attention to our company's products and thank you for your suggestions for improvement of our company's products. Our company's newly-listed FY6800 series signal generator will change the power supply plug to a three-core socket, which has solved the BNC leakage current problem.If FEELTECH products need to provide technical support, you can also send an email to feeltech@126.com and we will help you.
Good on the manufacturer to post a response and make changes! I feel better about ordering this function gen now!
You made me curious, I've had mine for years and always had to earth the ground otherwise it would give me a jolt. So got up in the middle of the night, measured it: 2mA!
Yes! AWESOME! I'm a projects hobbyist who hasn't formally been trained in EE, basically I have a learning ethic and more than that, a natural tendency towards DIY! I have watched this particular video over a dozen times in 2016, as I had dedicated most of the year to the study of POWER SUPPLIES! I catch valuable info every time, just now I'm reminded to 'Check the dataSheets of your voltage regulators for drop out scenarios.', this stuff is just what I need, and it was by pure coincidence that I had just bought this exact function generator and by chance, happened upon your video. THIS VIDEO HAS BEEN A HUGE, VALUABLE SERVICE TO ME! Very encouraging. Thanks a lot!
I like the way you explain electronics.I'm an electronics technician and i have learned a lot from this video.Honestly, i never came across the floating voltage problem.Thanks for this great channel
Thank you so much for running those tests, very much appreciated. I was expecting some issues with the waveform but for the cost held up better then expected. A very nice conversion of the PSU to a more suitable format and can be done very reasonably with 'junk' parts.
Nice mod! I love modding my electronics, I mod pretty much anything I can get my hands on. I just finished modding a KVM switch, it used a 12v SMPS for power and a 5v buck converter for the 5v USB rails, I wasn't happy with this design as the buck converter could fail short circuit and blow all my USB devices attached (over £300 worth) So I made a very high quality 5v SMPS with 2 over-voltage protection circuits and bypassed the buck converter. :)
Found your channel linked on Banggood's page for this item. The best video I have found explaining the design of a power supply. Very well done! Thank you.
Thanks
Hey. I just stumbled upon your channel as I searched for videos about LPS design projects, so this was my first experience of your video style. I'd say you have yourself a new subscriber! Awesome video.
Thanks Mark!
I seem to be late to this party, but I just bought one of these (yes, they are still the same). Saw your previous video regarding the leakage and went searching for a suitable but cheap linear. I found a "SL Power Electronics Linear Power Supply MTLL-5W-A" on eBay for under $20 shipped and it seemed like it would fit (physically and electrically) so I ordered it the same day. The generator and supply both arrived yesterday. My AC leakage was lower than yours but at 43V, and 0,4mA, still a concern to me as it applies to connecting it sensitive equipment. The SL Power unit fits very nicely into the 3224 enclosure and is rated at about twice the currents needed by the 3224. Installation was a matter of a little soldering of longer AC power wires and moving DC power input wires to suitable pins and connector on the new supply. Works Great! Unit still floats relative to power ground (I wanted that) and the leakage is now under 6V and current 0.7uA
I attacked this another way. I left the switcher in place and put a 1:1 mains isolation transformer in front of it. Did you find that the fully linear supply made the output any cleaner?
Awesome video. Thank you for your detail explanation on Power Supply design the reason why you are going linear rather than switching.
Nice video! I like the mechanical layout and your test for a savety operation. It is allways wise to use a permanent load at the regulator output, because the stability and regulation gets greatly improved. This could be seen with a load change measurement.
Great tutorial, well appreciated by a novice in electronics such as myself. I also have this signal generator and have built your PSU solution using the same transformers purchased from Rapid Electronics, however I have a problem which because of my limited knowledge in electronics fault finding I am struggling to put right.
My +5v and +12v are fine but I have no negative 12v output, just a load of random noise as viewed on the oscilloscope, and the dual 15v transformer is getting blisteringly hot at about 75 degrees C after about 5 minutes or so. I have my 5v rail on it's own heat sink and the 12v rails on their own much larger heat sink. None of the regulators are overheating and are sitting at about 25 degrees C, even as the transformer overheats. As I said earlier my lack of knowledge leaves me perplexed, I wouldn't even know how to interpret the oscilloscope output. I really love my electronics hobby and any help you could offer would be greatly appreciated. Thank's.
Are you insulating the 7912 from the heatsink? You do know that the metal tab on those is NOT ground, right?
Great upgrades indeed here Steve, I really like the explanations too into your circuit ideas & requirements. Awesome!
Cheers
John
Thanks John
My plan (after installing a 317/337 linear supply) was to put an IEC connector on it and add a switch to enable or disable mains earth referencing. Looking forward to your USB isolation.
I am working on something similar. Thanks for sharing.
Thank you very much for this video. You are a very nice man to share your work and find a sollution for this product, and i think the chineze sellers will be happy too when there is a sollution for their product. Is nothing wrong with making and selling cheap products. I am a big fan from Banggood. I am just a hobbyist, i am not building a sattelite here, just try to repair an old radio or something.
Very nice job (and superb video production, as always). For the "DAC"
one could look for the 8th-bit resistor and perhaps change it for one
that more closely matches the other 7 bits.
Yes, it might even just be an option to buy a few hundred and match them to replace all of them.
A good looking project. I'm intending to do the same to mine. Well, similar.
You've gone with two transformers and a fully linear design. I think for power considerations, what I'm intending to do is use a linear arrangement using 7812/7912 as yours for the +/-12V lines, but tap from the transformer down to a switching regulator (likely an LM2596) to generate the 5V line. Looking at the board arrangement, it only uses the 5V line for logic supply, but most of that is itself fed into the onboard 3.3V LDO, so I don't think it has to be that smooth. About the only thing the 5V line is used for directly is the LCD backlight - I'm sure that could put up with a bit of switching noise ;)
Yes, this sounds like a good plan. I realised afterwards that I still had an LM2576 which I could have used for the 5V rail, but the video hopefully served a purpose of showing how to design a linear supply. There's also an interesting alternative on the EEVblog forum using a pair of transformers to feed the existing power supply www.eevblog.com/forum/testgear/feeltech-fy3224s-24mhz-2-channel-dds-aw-function-signal-generator/325/
this is a good video thanks for your time in making it...
when i get mine ill be doing the same mods..
I got a 'tingle' so I took the option of changing the input to a 3-wire on mine but also fitted a switch to disconnect the earth if I wish to float.
Many regulators need a minimum load. It is not always direct specified but for the 7912 it is stated under output voltage conditions: 5mA ≤ IOUT ≤ 1A
+pa4tim yes has caught me out in the past even more 'fun' when its not stated !
+pa4tim Yes this is what I've found. Thanks!
It would be interesting if you could get a review unit of the newer FY6900 and perhaps the PSG9080 to bring things up to date.
Useful to know this has so much leakage current, personally all this linear power supply and fan stuff is a sledge hammer to crack a nut, as the device will work down to 85v I would fit a cheap 240 volt to 110 volt isolating transformer in the case, remembering that this approach will only work for 240/220 volt supply unless the transformer is reversed 110 volt to 240/220
Great video, only it come little too late, if you did it earlier i would not need to have discussion with some "experts" and try to explain to them how voltage look after rectifier diodes and capacitors (by the way it was on your video #030).
Miloš Lazović Thanks Milos
I normally get accused of over engineering designs with huge safety margins but I think this has outdone even me. I would use a toroid (I always use toroids) with dual 15v outputs. A very small transformer. I would take the +5v off the 12v rail and use clip on heatsinks at about 8c per watt.
First the 3watt will be dissipated across 3 devices. The hottest will be less than body temperature. Convection cooling with a couple of mesh covered holes at the bottom (near the front) and top rear panel will be more than adequate. The transformer will be stone cold. Also I assume this is at max output where the slew rate limits of the output op amps are going to wreck the waveform anyway. Most of the time it will be running an output of 3 or 5v p2p with correspondingly lower power requirements.
Over-engineering is what I do best :)
As an alternative how about battery power? Here is a multi output low voltage switcher with linear regulation of the outputs. www.banggood.com/DIY-USB-Boost-Single-Turn-Dual-Power-Module-Linear-Regulators-Multiple-Output-Power-Kit-p-1022517.html This gives +/- 5v, +/-12v and +3.3v at up to 300ma each.
I have a couple of these for project breadboarding. I also have a couple of programmable loads so will soak a unit to check thermals. The lowest input voltage is 5v so a 6v supply with schottky diode protection can provide power direct and be tapped from the power module for the +/- 12v. An external 6v battery brick is no more inconvenient than a mains brick eliminating mains risks.
That's quite a neat find, and could be useful for someone wanting to replicate. Thanks
So using batteries along with that supply kit, would it also provide isolation of the generator outputs ?
My alternative noob question would be to know if it's always better to have floating generators or if there are drawbacks you need to know abou, and would you recommend a simpler earthed PS and/or outputs mod for not so experienced users ?
Eldon Tyrell Most professional equipment has non-floating outputs. The only real issues this poses to a piece of equipment such as a signal generator is that the offset may not be adjustable enough for your purpose - say for example you wanted to use the generator to inject a signal to part of a circuit already at 20V relative to signal ground.
Whether this is important to you depends on your circumstance.
I suggest to consider for the calculation of the capacitor (or 2° of the transformer), the supplied voltage of 210Vac (instead of 230) to compensate for the line voltage drops in rural areas or peak hours of absorption.
Hello, fine tweak you got here. Wondering WHY you have choosen 2 TRAFs w/2 separate bridges and ground instead of a SINGLE one derived from the MAIN 12+12 bridge w/ same ground. Any particular reason or just thinks it is better?
Very nice design I would have move the back BNC's more to one side and mount the heatsink on its outside in the back ! But all and all nice mod !
A couple of people have asked the same question I wanted to raise but can't find any answer from you. I was wondering why you didn't derive the necessary rails (+12v, -12v & 5V) from one dual secondary 12V transformer with 7812,7912 & 7805 regulators?. No heatsink (or very minimal heatsink on the 5V regulator fed by the 12V regulator) would then be required. Perhaps I'm missing something.
Very professional; "thumps up"
Oops, you answered my question re: earthing at the end of video..
I'm thinking to do same modifications, but with only 1 transformer 2x 12V, and set the 5V from the resulted +13V DC, before the 7812.
Very good video. Thank you!
I would mod that panel to take the fused IEC connector, as the output sockets are going to be accessible metal in case of insulation failure on the transformer. Then connect the transformer cores only to mains earth. You could use a smaller heatsink though.
+SeanBZA The transformers are double insulated, so according to the IEC standard no earth is required even if there are accessible parts on the secondary of the transformer.
Nice upgrades! :)
Thanks
hi sir,
i brought a new rigol ds1054z when i on channel one....i can't hear the sound of relay
thanks for video, i think for isolation we can insert only 1 isolation transformer (220VAC to 220VAC) between AC input and power supply board :)
Hi! Very nice video, but I wanted to download the schematics but, the website is being redesigned. When will it be available again?
For us neophytes, are there any linear power supply kits you could recommend to replace the factory supply? Thanks!
19:11 I had similar experience with LP2951ACMX/NOPB. It's output voltage is not steady and have dependance to input voltage and load. And datasheet says nothing about it. Or am I doing something wrong?
I know that it wouldbt be as elegant a solution but would just putting a small isolation transformer on the mains line before the stock power supply have also worked?
Do R/C! Yes, if you can fit one in or have one to hand! Good luck!
Nice work, but what is all the extra space for inside that case?. Why not make it as small as they can so it takes up as little space on the test bench as possible? It would be nice to have that space for other test equipment.
Hi! I´m a newbie ham, building my very first ham shack. I got an old oscilloscope for free from my father, which he himself once got for free from a physics lab when they upgraded. It´s a TeleQupment S54S, very old. I am looking for a rf signal generator and the Feeltech fy3200s fits my budget. I looked at your very nice vids on mods, but also noted you mentioning that other users have been reporting varying amp levels from the BNC connectors originating from the switching psu, which seem to vary regarding components chosen from unit to unit quite a bit., Is the leaking current usually as high as in the unit you have? I will be experimenting with the oscilloscope and a signal generator, learning the very basics of different uses and for antenna and feeding line testing for instance. I read some people suggesting bypassing the inboard psu and use a lab psu instead. Could I instead find a suitable wall wart from an electronics store and connect this to the pcboard power connectors? Is there such commercially available transformer based linear psu wall warts anymore? I´m probably not going to use the usb-port. Maybe I could find the same rf signal generator without the case and psu? Then again, is it possible that the manufacturer of the Feeltech 3200s by now has rectified the problem? It would seem that the Feeltech fy3200a is a good choice for a newbie with a low budget like me, but that current leak bothers me. So, I have a lot of questions on my mind, forgive my ignorance, but we all have to start from scratch as newbies....and forgive my bad English, I only speak Swedish and Finnish well. Loved your vids, learned a lot!
It would be really interesting to see if you could figure out a way to improve the signal quality at higher frequencies (and/or higher voltages). Perhaps some better opamps for the output, would solve part of it?
Hi where did you get the +-12v and 5v power supply board, I have looked everywhere. Thanks
Nice video, but shouldn´t it be enough to use an isolation transformer to get rid of this unwanted leak?
Hi if I connect the bnc of my high voltage floating Feeltech signal generator to a mains grounded bnc of my osciloscope always will this pose danger to my DUT or ground loop problems?
Could the 2x15v transformer not be used to provide power to the 5v regulator and simplify the circuit somewhat?
hola , perdón por preguntarte en otro idioma .
Me interesa este generador pero tengo una duda -
HAY ALGUNA DIFERENCIA ENTRE EL FY 3200S y FY3224S ?? los vendedores los ofrecen pero tengo dudas de cual comprar ,...gracias
My first thought was to simply use an actual isolation transformer (example: Triad Magnetics N-48X) and to retain the switch-mode power supply inside the unit. US $20 (with shipping) and running in a few minutes. Beef up the internal power leads in the process.
If anyone in interested, I purchased one of these from Banggood for $50. I isolated the AC input using a Triad Magnetics N-48X isolation transformer, and (as anticipated), the AC feed-through was removed. The transformer fits easily inside the case, and it mounts to studs on the case that were included by the manufacturer. Less that $70, total for a decent Arb (unneeded, since I have had an Arb on my bench for almost 20 years). OK, overkill.
Sounds like a fine solution, but don't forget to isolate the USB connection as he explains in his next video.
Such isolation is important only if used with a PC that has is electrically connected to ground (many notebooks are isolated). However (IMO), it is not necessary to design an interface. This one from Banggood, which I purchased, works fine and is less than $9: www.banggood.com/High-speed-Isolation-USB-To-TTL-Serial-Module-Power-Isolation-Optocoupler-Isolation-p-1230932.html?rmmds=myorder&cur_warehouse=CN
Hi, i have a model of the previous series, the FY2200 that was sale in the 2,6,12Mhz versions, my is the cheaper, the 2Mhz, do you know if it possible to increase the maximum frequency ? It has the same altera chip and it looks very similar... Anyway great video!
Very nice job indeed. Just wondering are both terminals of the fuse holder shrouded/recessed/hidden on the outside? ie because either terminal could be live. Thanks for sharing.
Hi, yes, this fuse holder is quite nice - neither of the connections are accessible from the outside when the fuse is removed without poking something right into it.
Could I simply earth the BNC connectors, thanks, good video..
I am buying parts to make the linear PS for the Function Generator...Will these transformers work? EI35 2W/2VA Power Transformer Input AC 220V 50Hz - Output AC Single/Dual 6V-24V I dont quite understand the 2VA rating. Thanks for your time.
Seems like a lot of trouble to go through. Why not simply use the two transformers to isolate the existing supply? Connect the two six volt windings together, and one primary to the mains, and the other to the supply input. Done!
Nice video! I have orderred the same unit from Banggood and looking forward to play
with it...! I was wondering why did you not just modify the power
connector to a grounded 3 wire connector so that the ground would be at
zero? Would that not fix the issue of leakage that you find on this
unit? Surely if the original ground is floating, bringing to a solit
houseold ground would fix the problem in my view? Any comments?
Suppose you want the output signal to be relative to a signal level other than ground. E.g. a MOSFET gate with the source terminal hooked to 12V or 48V. Maybe you can do some of this using the offset, however power-up and -down remains a problem.
If the signal generator output ground is tied to AC ground, it becomes harder to use and less flexible.
Can you avoid linear voltage regulators with a 12V and 5V transformers instead of your greater voltage ones?
Are you using the right instrument to look at the output waveform? Your MSO1074 seems to have a bandwidth limit of 70MHz (despite the 1Gsps spec) which suggests you will not see an accurate waveform representation of the 24MHz output (3rd harmonic is 72MHz, yes? On the edge of your scope, perhaps?) Mind you, if you can see the distortion on this scope, it suggests it's probably much worse. But still... And was the monitored output correctly terminated?
Hi, the MSO has the 100MHz option enabled, but it's still possible. I put some more waveforms on my website from a high bandwidth Keysight scope 50R terminated.
Thanks for sharing this - I am planning to build something like this up myself. Might even get some PCBs done which would leave some over for others. Out of interest, do you have the various connector part numbers / series for the power connections?
The actual connectors used on the front PCB are JST XH series (the contacts are BXH-001T-P0.6, housings XHP-6 for the 6 pin versions). I used Molex KK connectors on my veroboard.
Thank you for sharing! Will be good info for others too I hope :)
Would it work to install an isolation transformer between the mains and the switching power supply rather than replace the power supply?
I had the same question and I think that is the safest way without building a power supply. Those direct mains power supplies can even be dangerous if bad things happen inside the unit. Never attempt to attach any test equipment (scope etc.) without an isolation transformer unless you are attempting to get burned, destroy the unit or commit suicide.
I can see you have a very nice collection of PEAK instruments, do you already made a review?
Hi Pedro, if you look at my earlier videos I have reviews of the LCR meter, the DCA and the ESR meter. I didn't get round to doing a review of the ZEN.
Thank you, for shure I'll enjoy your reviews, Cheers
do you fix synthesizers ? if so how much do you charge for an assessment ?
Instead of replacing the existing switching power supply by several linear PSPs, why don't you simply feed the function generator via a common 1:1 220V (ca. 50W) transformer?
Yes this is a valid solution, however I wanted rid of the SMPSU - it was a little noisy and has no place in a function generator. I also wanted this to be a basic tutorial for designing linear power supplies. Thanks for watching :)
As a tutorial for designing linear power supplies your presentation is great. :)
Thanks for your comments
I having problem with minus 12 volt I did check the schematics still no voltage
Maybe I missed it, but what is the small device below the 3 pin connector use for? I didn't hear you mention anything about that.
Do you mean the device in the DIP-8 package? That's the 1A bridge rectifier.
SDG Electronic Yes, I see that now. It was late when I was watching. Do you have a drawing for the acrylic base you made that includes the dimensions for the holes etc? I just bought one of these for $65, couldn't pass it up. For my needs, I think this will work just fine.
Thank you for this video. Could I ask what sort of software you use to record two cameras simultaneously and would you recommend it? Thank you!
I've always used Adobe Premiere. It can sync videos on audio
@@sdgelectronics I see. Thank you very much for the prompt reply. Much appreciated sir!
What would happen to the -12V regulation if the LED on the -12V rail were to fail at any point?
+Adam Edelberg Probably nothing much as the -12 V feeds the opamps in the output stage. These are likely to consume more than 5 mA. And even if they didn't and the -12 V would become -15 V, if the opamps can handle -15 V then nothing would break. Besides that, LEDs rarely fail as long as you treat them properly. And at 6 mA, they should work for an eternity.
+Peter-Paul Vervoort Thanks Peter-Paul for replying to a lot of recent questions!
nice peter! in canada due the the 60hz i often find 4700uF caps in psu's im partial to 470-4700 @ 50V Negitive VR's require a negitive Rail. such as -12 as compared to a Plus voltage If you are going to do a 2nd part......Might i suggest adding a Vent Fan?
+Amy Marie Yep, a small fan may be in order. It gets warm, but not hot. I'll do some measurements :-)
Look forward to the 2nd part.....
Why you haven't grounded the BNC shields?
+Jacek Pawłowski I purposely want the signal generator to be floating so it can be used at elevated potentials.
At 3:50 and so.... wouldn't it be a good idea to zero the clampmeter before taking a measurement? one can see, that it's floating around 30mA unconnected. quite a significant shift for the measurement.
what does the square wave look like?
+Daniel Rowe I'll capture a few waveforms and add them to my website.
Waveforms at the bottom of the page. sdgelectronics.co.uk/feeltech-fy3200s/
super nice, however we can see how inefficient linear PS are ;-)
Such a huge heatsink but no way for the heat to get out?
Simon Turner see video 33
Building a linear replacement for the switch mode PSU seems a bit OTT.
Why not use 1:1 isolation transformer between mains switch and the switcher and keep the switcher? If you can't find a small 1:1 transformer use two 1:n transformers back to back. The VA is tiny so they will be smaller and cheaper than a linear replacement plus heatsink. Give the brain a rest and do it the easy way!
You can buy USB isolating 'cables' if that is a real problem, but I doubt if I'd ever want to ever want to use the thing floating whilst driving it from a PC. In fact, the software is so incomprehensible I doubt I'd want to use it, ever!
I could do, but I also wanted a linear power supply tutorial. I also wanted to eliminate the swicher altogether.
@@sdgelectronics Thanks for doing this video. I'm a hobiest, and even after seeing your work, I bought this unit. It works well for my purposes. I'll be adding a simple isolation transformer.
I thought AC RMS value is 0.707 voltage of peak positive , how does the Negative RMS Voltage 0.707 get placed on the postive portion of the voltage? Nevermind as the power supply is a +12 and -12 output...so its 1.414...= Duh on my part.
Was suprised how low frequency it starts to distort waveform...
+Jurva-Markus Vehasmaa I might investigate what is causing the issue. I suspect rather than adjust the reference voltage to the DAC, they just represent the sinewave with fewer numbers of bits, so it's probably a combination of the GBW product of the amplifier stage, or purely not enough resolution.
+Jurva-Markus Vehasmaa I guess you mean, low amplitude ? My guess is that there's no proper attenuator circuit after that R2R DAC (or an attenuator with a limited range) so the lower amplitudes are made by using only part of the DAC's bits. So at lower amplitudes the DAC would behave as 4 bit instead of 10 bit for example.
Peter-Paul Vervoort That's exactly it.
That heatsink is way overkill for the amount of power that those regulators are dissipating. And, vertical fins would get rid of the heat a lot better than horizontal ones. Also, the choice of small-value capacitor to put on the outputs of the regulators isn't as arbitrary as all that. The datasheets that I recall specify something like 1-10uF _tantalum_ or 25uF electrolytic. I'd be putting a smaller valued cap across there as well, say 100nF plastic film. The point is not only noise reduction but to keep those parts from oscillating.
Not true, two channels into 50R loads results in quite a large temperature rise. The heatsink and fan is required
oscilator z led diy semafor
what happen to usb video
Hopefully this weekend. We've all been ill so didn't get it done when I'd hoped last week :-(
could not wait mate thanks let me now
sorry wrong post
its more fun to build .rather than buy....
$70.00 USD FY3224s, additional parts $60.00 ?? so $130.00 ish so basically around the cost of a Brand new Instek SFG-1003 or buy a used B&K Precision Model 4040A
I think I spent £15 in extra parts. The Instek is only 3MHz.Obviously used equipment may be better value
+SDG Electronics , best I can see the 2 transformers alone are like £22 + £20 shipping. I'll wait until you post a parts list and prices like to see where your getting the £15 from, sounds like a great deal for parts.
+Martin P Hi Martin, the transformers are a lot cheaper than that - Rapid Electronics sell them for £4.30 each (e.g. Order Code: 88-3710), CPC also (order code TF01331). The regulators are around £0.50 and capacitors total less than £2. Then there is just perfboard and the heatsink. If you're in the US, I'm certain Digikey have similar.
Looks like a lot of empty space inside that box
Nice reverse engineering ,I hate switching supply with a vengeance they are engineered to save coper cost and are sold in modern equipment at the same cost as a good linear supply who have proven themselves to last for ever the only maintenance they need it's to change the capacitor every 20 years and go on for another 30 more years ,they are ton off vintage guitar and radio using tube with linear supply still working 60 years latter , and switching supply are really dangerous I had one in the digital display of our dishwasher turn off who took in fire in the middle of the knight the build in fuse never worked the PCB board of that switching supply burned a hole on the pcb really scary if we wouldn't have been there the whole house would have burned ! These switching supply have infected all of our modern electronic since the late 80 ,you can find some even in our LED lighting bulb replacement ! You just extended the life of this signal generator for 15 years if the rest of the chinese parts live to do their parts ..
Mine shows a DC component between GND and the core of the plug of the channels! Even if channel is disabled!
Any way I could fix this?
oscilator z led diy semafor