| Electronics > Projects, Designs, and Technical Stuff |
| EMC testing, problems with MeanWell power supply |
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| chris_leyson:
--- Quote ---I've done something long time ago. For something like this, an engineer has to be present during testing. That kind of pulse will bypass filtering and re-radiate inside the case, then gets picked up from all kind of places. In our case, R/W line of Z80 board has to be tweeked with small capacitors. Also, cabling had to be re-routed. It's not something you can guess from non-technical third party's statement. --- End quote --- I tend to agree with tkamiya, you've got a very fast pulse, several kV with a 50ns risetime, on any combination of L, N and Earth. I've recently had to test a device at 4kV and it still had to function flawlessly, not an easy task by any means. The product also had a small 15W flyback supply built in. Secondary side regulated controllers worked flawlessly, not even a tiny glitch on the output whereas a few primary side regulated controllers either stopped working during the EFT pulse, went into a shutdown mode for 200 to 300ms and one let the magic smoke out. Sanken STR4A100 series flyback controllers get my thumbs up. As for the rest of the electronics you have to increase the test voltage until something fails functionally and then fix the problem with additional decoupling caps either on the supply or signal lines, then rinse and repeat. Good luck with your investigation. |
| honeybadger:
--- Quote from: Gyro on March 16, 2019, 01:59:03 pm --- There is absolutely no point in having someone non-technical accompany the equipment to the test house, you should be there, no excuses! --- End quote --- My colleague is quiet eager so he will try it with a different PSU next week. If this fails I will be there in person next time - I am not able to clone myself. Now assuming it is not a PSU fault. And he transients go through. What can I do? What should I prepare? As I wrote, there are TVS diodes (TransZorb) already - are they fast enough for these surges? I can add another ferite to the power cable. Should I add MOV in parralel to the TVS diode? I guess adding few 1uF MLCC to the Arduino and LCD wll not hurt (there is a few 100nF already) Damn, I hope it is the PSU! --- Quote from: ebastler on March 16, 2019, 02:46:25 pm ---"My circuit does no longer work after the 2kV spike, so the PSU must no longer be supplying the appropriate power to it". ??? ... Your regulator for the 5V rail may provide additional filtering, so the 5V devices don't experience a problem; but the devices running off 12V do. --- End quote --- The only evidence I have is the video from my colleague. There is an NPN transistor switching a relay (12V) and a LED (with a resistor in paralel with the relay coil). After the 2kV spike the LED blinks but the relay does not click - this is an evidence for me - there must not be enough voltage for the relay to click. The relay is powered directly from 12V rail - there is no VREG there. There are no "smart" devices (which can lock on) on the 12V rail - only relays, NPNs, LEDs and passives. |
| wolfp:
What kind of pulses are you talking of? Surge acc. EN 61000-4-5 or Burst acc. EN 61000-4-4 ? The first one is a single shot 1.2/50 usek with rather high energy. To handle this you need transient-absorbers or MOVs. A surge sometimes destroys your components. The second one is more comparable to a high frequency signal 5/50 nsec, it is radiated from the wires and if it succeeds to get into your circuit you can find it anywhere. Because of its high frequency and low energy it can be blocked by ferrites or small capacitors. A Burst normally disturbs but not destroys. Wolfgang |
| ebastler:
--- Quote from: honeybadger on March 16, 2019, 02:59:15 pm ---There is an NPN transistor switching a relay (12V) and a LED (with a resistor in paralel with the relay coil). After the 2kV spike the LED blinks but the relay does not click - this is an evidence for me - there must not be enough voltage for the relay to click. The relay is powered directly from 12V rail - there is no VREG there. There are no "smart" devices (which can lock on) on the 12V rail - only relays, NPNs, LEDs and passives. --- End quote --- Thanks; you had not described it quite like that before. Having the relay and the LED in parallel, and only the LED operating, might indeed suggest some persisting problem with the voltage supply. Meanwell provides quite decent datasheets and compliance testing information on this power supply: https://www.meanwell-web.com/en-gb/ac-dc-wall-mount-adaptor-output-12vdc-at-1a-input-gs12e12--p1i Their test report summary suggests that EFT testing has only been performed with a 1kV surge (which they claim to be the requirement for "light industry" environments): https://www.meanwell-web.com/content/files/pdfs/productPdfs/MW/GS12E/GS12x24-rpt.pdf |
| honeybadger:
WOW, than you for these links for certifications! I was not able to find these and my local Mean Well supplier does not know anything. |
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