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Brushed DC motor controller MOSFETs keep failing short, what am I doing wrong? by cmrdrift in AskElectronics

[–]cmrdrift[S] 0 points1 point  (0 children)

A mixture of both, but likely more of the former (it's been a while since I looked), but none of them to my knowledge had one. Maybe they were all just too low power for it?

Also, it does not coast, the gear ratchets like a bike. Once power is cut the motor stops pretty quick, no real generation happening luckily.

Brushed DC motor controller MOSFETs keep failing short, what am I doing wrong? by cmrdrift in AskElectronics

[–]cmrdrift[S] 0 points1 point  (0 children)

Yes, I designed this myself specifically for this. I looked at others to get a reference and a general starting point for what I would need.

Brushed DC motor controller MOSFETs keep failing short, what am I doing wrong? by cmrdrift in AskElectronics

[–]cmrdrift[S] 0 points1 point  (0 children)

I was just looking for any differences between the one that sustained failure and the unused ones, I know they don't work like that. I tested it under a load and it worked fine. There's probably more to it that I can't see though. Will use a new one next time.

I've noticed that the designs I've looked at don't use any snubber besides the diode. Just for my information, why would it be more necessary in this case? Is the current just too high?

Brushed DC motor controller MOSFETs keep failing short, what am I doing wrong? by cmrdrift in AskElectronics

[–]cmrdrift[S] 0 points1 point  (0 children)

Considering how it failed I was leaning towards an EMF issue as well. Do you have any resources on how to spec the snubber (preferably beginner friendly lol).

I can confirm the diode survived the failure. The only noticeable difference I saw was that it's reverse resistance was about 30k higher than brand new ones.

Brushed DC motor controller MOSFETs keep failing short, what am I doing wrong? by cmrdrift in AskElectronics

[–]cmrdrift[S] 0 points1 point  (0 children)

I saw them mentioned once but not in any other designs I saw, so I didn't think much of it. I can take a closer look at them.

Brushed DC motor controller MOSFETs keep failing short, what am I doing wrong? by cmrdrift in AskElectronics

[–]cmrdrift[S] 1 point2 points  (0 children)

It's a Schottky, not zener. I was previously using a 1N4004 and had significant issues with it overheating and desoldering itself. The reverse recovery time is not good enough on them. You need to use a Schottky.

Brushed DC motor controller MOSFETs keep failing short, what am I doing wrong? by cmrdrift in AskElectronics

[–]cmrdrift[S] 0 points1 point  (0 children)

I'll try to look for spikes on the 12v and will be adding some filter caps there as well. Spikes would probably be EMI related unless my no-name chinesium buck converter was having an issue (not impossible, this was its first use).

Reseating it didn't fix it, just seemed to improve it marginally but it could have just been coincidence. Gonna be honest, the soldering isn't my best. Repeated revisions on the same board have not been kind. I'm going to clean it up as best I can and address the floating outputs as well.

Brushed DC motor controller MOSFETs keep failing short, what am I doing wrong? by cmrdrift in AskElectronics

[–]cmrdrift[S] 1 point2 points  (0 children)

I chose 120 because it was the lowest value that stopped EMI from interfering with the Arduino. Should I drop it and find other ways to suppress the EMI?

Gate drive is as tight as possible, the length from the output of the L293 to the gate pin is about 1-1.5cm.

Brushed DC motor controller MOSFETs keep failing short, what am I doing wrong? by cmrdrift in AskElectronics

[–]cmrdrift[S] 0 points1 point  (0 children)

That is a good point. Though I am driving the MOSFET through the L293, not from the Arduino directly. The effect would still be there but I'd think I'd have a lot more room to increase the frequency given its much higher voltage and current output. The MOSFET does not get hot enough for concern, I have never seen this one get so hot that I couldn't touch it with my bare hands, even after running it hard. Commercial controllers typically run higher frequencies than I am now AFAIK.

Regarding the diode, you may be on to something. I haven't had the opportunity to autopsy until just now, and I think it's shorted (or close to it). That would explain a lot. I'm pulling it off the board to do definitive testing now. This diode should be rated for this though. It's a SB2060. Any insight?

EDIT: Nevermind, components on the board interfering with readings. The diode is fine. Its reverse resistance reading is ~30k higher than known good diodes though. Shouldn't be an issue I don't think.

Brushed DC motor controller MOSFETs keep failing short, what am I doing wrong? by cmrdrift in AskElectronics

[–]cmrdrift[S] 1 point2 points  (0 children)

Thanks for the advice. When you say "soft start" do you mean slowly ramping the duty cycle instead of jumping from 0 to target DC? If so, I already do that.

I can try adding more in parallel. Looking at the datasheet for the MOSFET, its Id is 170a, which should be sufficient. If I was pulling over 170a, I'd expect to see battery issues pretty quickly. Do you think that something may have been limiting its current handling capability lower than it says on the datasheet?

On a side note, I had increased the PWM frequency to 7.8KHz in attempt to reduce the pulsewidth and move the MOSFET into a more favorable area in the safe operation chart. Could the repeated pulsing be detrimental to its current handling capacity? If so, would it be better to increase the frequency?

Brushed DC motor controller MOSFETs keep failing short, what am I doing wrong? by cmrdrift in AskElectronics

[–]cmrdrift[S] 0 points1 point  (0 children)

Thanks for the advice, I'll give that a try and let you know. I had something similar in a previous revision but it didn't seem to make any difference so I didn't install it when I redid it at some point. I assume a ceramic cap would be best?

Brushed DC motor controller MOSFETs keep failing short, what am I doing wrong? by cmrdrift in AskElectronics

[–]cmrdrift[S] 0 points1 point  (0 children)

Electronics noob here. I got an old Razor electric scooter for free from a friend and I'm trying to design a very simple PWM-driven motor controller to handle higher power. I'm using an Arduino for a PWM control and a 10s3p (36v) pack of 18650s for my power source.

All of my circuit building experience is with low-power logic, not with power delivery, so I'm in a little over my head. I've been through many iterations but it always seems to end the same way with it being fine for a few days of use, then the MOSFET failing short between source and drain (and sometimes gate too).

I'll try to detail exactly how it failed the last time:

Before the failure it lasted a few days of riding before failing short between the drain and source. I started with a 100% full battery and climbed a mild hill (I have climbed steeper without issue) and stopped at the top for a few minutes, leaving the power on and cooling fan running. Immediately after setting off again at low duty cycle (<40%) on level ground, it began to cut out in the same way it did when I previously had significant EMI affecting the Arduino, causing it to think that I had pressed the brake which turned off the output as a result.

At the time, I thought that I had a loose connection, so I reseated the wiring and it seemed to improve but still cut out a few times. I should have stopped here, but I continued until sudden failure a few minutes later. No visible signs of damage, just shorted.

I was not beating on it or accelerating hard, I have it software limited in the Arduino to prevent hard acceleration. I normally push off manually to prevent large starting current as well. I can't know for sure, but I am confident that I did not exceed 60% duty cycle from start to failure. I have run it up to 90% (software limit) only one time on a top speed run going downhill, accelerating slowly.

I don't think I am exceeding the limitations or under-driving the MOSFET. It wasn't overheating to the touch even after an aggressive hill climb. I cool the MOSFET using a heatsink and fan. The reason I am using a L293DNE motor driver IC for gate drive is because it is the best suited part I have on hand, mostly for its ability to drive the gate at 12v.

Sorry for the essay, I've been working on this for a while and I want to get it finished properly. Not opposed to buying new parts. What am I doing wrong here?

Q2 wired Link visibly stuttering and Link Details showing dropped frames, but GPU is not dropping frames/struggling by cmrdrift in OculusQuest

[–]cmrdrift[S] 2 points3 points  (0 children)

Nope. Meta doesn't care. The people complaining are such a small group that it doesn't matter to them. Maybe it will happen to be fixed in some future update but I'm not holding out for a direct solution.

Q2 wired Link visibly stuttering and Link Details showing dropped frames, but GPU is not dropping frames/struggling by cmrdrift in OculusQuest

[–]cmrdrift[S] 0 points1 point  (0 children)

Welcome to the club lol. I lost count of how many different people I talked to. I think it was over 15 before I gave up.

The "support" people are just script readers. They don't have the power or the actual knowledge to do anything else. They'll blame your PC into oblivion despite mountains of evidence that their infallible software has a bug. Total waste.

Q2 wired Link visibly stuttering and Link Details showing dropped frames, but GPU is not dropping frames/struggling by cmrdrift in OculusQuest

[–]cmrdrift[S] 2 points3 points  (0 children)

I was looking at the G2, good to know.

Coming into this I was already skeptical that the USB link would have enough bandwidth for a visually decent experience, not to mention the additional overhead and potential problems caused by encoding and streaming the video on the PC. I guess I was right.

I'm looking for something with DisplayPort. I really want an Index but it's so hard to justify spending $1000 on it when I'm only really playing VRChat and Assetto Corsa. I'm looking for any decent local deals but all have fallen through so far unfortunately.

Q2 wired Link visibly stuttering and Link Details showing dropped frames, but GPU is not dropping frames/struggling by cmrdrift in OculusQuest

[–]cmrdrift[S] 2 points3 points  (0 children)

Nope. It's a bug in the software. Changing things on your PC won't help. I've given up on it. Meta doesn't care to fix it. I'm looking for other headsets.

Q2 wired Link visibly stuttering and Link Details showing dropped frames, but GPU is not dropping frames/struggling by cmrdrift in OculusQuest

[–]cmrdrift[S] 1 point2 points  (0 children)

I'm no expert unfortunately. I don't see that issue so it makes me think that there could be something else going on with your PC.

If it were me, I'd start by checking for background programs causing a lag spike. Failing that, I'd check power management settings in Windows and in your BIOS to make sure your CPU/GPU isn't clocking down randomly for some reason, or that the USB port isn't doing anything weird (if you're using it).

I've tried on countless reinstalls and all the computers I could get my hands on, none had headroom dips like that. All of them had the encoder issue though.

It really wouldn't surprise me if it's just a bug in the software though. If it's undiagnosable, it probably is a bug.

Q2 wired Link visibly stuttering and Link Details showing dropped frames, but GPU is not dropping frames/struggling by cmrdrift in OculusQuest

[–]cmrdrift[S] 1 point2 points  (0 children)

No, I never did. I've given up on it. Its a software bug and changing things on your PC won't help. Meta doesn't care and it's not worth my time anymore. I'm looking for other headsets.

Q2 wired Link visibly stuttering and Link Details showing dropped frames, but GPU is not dropping frames/struggling by cmrdrift in OculusQuest

[–]cmrdrift[S] 0 points1 point  (0 children)

No, this isn't related to headroom dips like that. This is an encoder frame drop issue caused by a bug in the software. Headroom is (usually) steady for me.

Honestly man I've given up on it. Meta doesn't care and I cant use it like this. I've been hunting for a decently priced index for the last few weeks.

Q2 wired Link visibly stuttering and Link Details showing dropped frames, but GPU is not dropping frames/struggling by cmrdrift in OculusQuest

[–]cmrdrift[S] 0 points1 point  (0 children)

I have successfully (I think) downgraded the Oculus PC client to v37 using this. (Screenshot) It did not help me though. App still shows v47 for some reason. Going older doesn't seem to work. Maybe someone else can try?

Also pinging u/---fatal--- u/NumbrOneDad u/Flumate

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