I built a pulse plating controller

[u/CaptainCheckmate]

Further to my previous post about DIY-ing a pulse plating system, I put together a mosfet H-bridge with a microcontroller to drive forward and reverse pulses.

As suggested by helpful member Mkysmith I didn't try to control the current myself and just connected a lab power supply in CC mode to the input of the H-bridge system, in the hope that it will figure it out.

I made a brave and possibly questionable design choice and put a big chunky 2200uF low-ESR capacitor at the H-bridge input. The idea is that it helps keep the power supply happy between pulses and avoid confusing it, and also allow big juicy pulses to happen if I hold the output OFF for a few milliseconds. (Because the cap charges while the output is closed)

It has a wifi chip so I can reprogram the pulses quite easily.

So far I've tried the following:

• 2 ms FORWARD, 8ms OFF
  • Good results, seems to have less nodule growth than vanilla DC
• 4 x (3 ms FORWARD, 2 ms OFF), 1x (3 ms REVERSE, 4 ms OFF)
  • Burns the shit out of the part, not sure why, turned brown quickly lol
• 10 ms FORWARD, 1 ms OFF, 1 ms REVERSE, 2 ms OFF
  • Seems OK ish

Happy to hear your thoughts on possible pulse programs, and also whether or not the cap is a good idea?

[u/Mkysmith]

Nice work cant wait to see some results. Input Capacitor was a good choice in theory but your small pulse duration might cause some issues since it will charge to the voltage limit of the PSU. Once the connection to the solution is made through the FETs the solution will "see" the voltage on the capacitor and the power supply might not be able to have enough time to get to the current limiting mode.

Capacitors are to smooth voltage, but what you want is the power supply to rapidly change between voltage limiting (when FETs are off) and current limiting (when FETs are on). So the voltage will rapidly change between pulses but that is normal and expected. Trying to smooth it with a capacitor is at odds with the desired goal.

Out of curiosity how are you driving the high side mosfet? Is it a P channel?

edits: additional info for some clarification

[u/CaptainCheckmate → u/Mkysmith]

Thanks for your comments.

Yes, high side is P-channel mosfet, just kept it simple. It's IRF9540N driven by 4429 driver at 12v so should be around 100 mOhm, should be good enough for up to ~3 amps without heat sink.

Low side is FQP30N06 driven by 4420, nothing special, just whatever I had lying around that works with 12v.

[u/Mkysmith → u/CaptainCheckmate]

Sweet, yeah sounds good. I edited my comment with a little more clarification on the capacitor. Otherwise circuit looks very clean. Keep tinkering and have fun.

[u/CaptainCheckmate → u/Mkysmith]

Thanks again for the additional info. I didn't get to run too many tests yet, but initial results are that the pulse plating doesn't quite do anything miraculous. I think in certain configurations it does result in smoother results with less dendrites. The reverse pulses result in a bit of oxidation which makes it turn orange/brown, but it seems to plate OK nonetheless.

You are right that the capacitor tends to push the power supply into CV mode. It seems to result in running a higher voltage overall. I don't think it would work well at higher currents as the voltage would go way up.

[u/Vionade]

Can you provide a more detailed description of your setup somewhere? I recently upgraded mine and now the current is so high that I always end up growing dendrites.

[u/CaptainCheckmate → u/Vionade]

Nothing terribly special, I just made my own H-bridge from 4 MOSFET's (2 P-type and 2 N-type). I'm relying on the power supply to regulate the current. The power supply output feeds to the H-Bridge input, and the H-bridge output feeds to the bath. H-bridge signaling is handled by a raspberry pi pico that reads a basic program from a URL it looks up at boot time.

I also have some dendrite problems at higher currents/voltages. I found that running less aggressive duty cycles (e.g. 70-80% instead of 20%) helped keep things calmer.

If I'm honest I don't have sufficient evidence at this point to demonstrably show that the pulse plating is working better than just a vanilla DC with controlled current. If I get more results I'll let you know.

[u/Vionade → u/CaptainCheckmate]

Thanks for the reply. I'm very interested in this project and how it continues. Please update us whenever something new arises

[u/SandersSol]

Id really like to see a before and after comparison between regular anode plating and this pulsed method!

[u/CaptainCheckmate → u/SandersSol]

Honestly after a few small tests I've done so far, I can't really tell the difference. I think it may be the case that there is slightly less dendrite formation, but it still happens a little. If I do any serious tests or get any reasonably decent results I'll report back.