5s + brake = magic smoke?

Info and Discussion about the ESC32 hardware and software

5s + brake = magic smoke?

Postby cecca » Tue Jun 24, 2014 5:04 pm

Hello everybody, I'm new on this forum.

I received my first ESC32 a few days ago, just took one for testing.
I was planning to use it with 5S battery, Sunnysky 3508-380kv motors and 15x5.5 carbon fiber props.
I loaded FF and CL terms from esc32_motor_db.xml, motor model="MN3508-29", prop model="RCT 15x5.5cf" and enabled closed loop mode.

It runned pretty well, probably better than any other ESC I've ever tried, but I wanted more, and decided to try enabling FET_BRAKING.
I was very happy on how it was running, but after about 30 seconds of throttle movement magic smoke came out. I pulled the battery as fast as I could.

High side FET on channel C has completely burnt, also low side FET has been damaged, but is less visible, other components seems fine.

Any idea on why this happened?
I'm going to replace those FET's, what can I do to prevent this from happening again?
I'd really like to keep braking enabled...
cecca
 
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Re: 5s + brake = magic smoke?

Postby JussiH » Tue Jun 24, 2014 5:22 pm

Fet braking is experimental and was AFAIK never proved working on ESC32 V2. You should disable it, or run the risk of burning more FETs.
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Re: 5s + brake = magic smoke?

Postby cecca » Tue Jun 24, 2014 6:23 pm

Thank you for your fast reply.
So, what's the problem with braking? Can't we do anything to make it work?
AFAIK it works well on different ESCs with simonk and blheli firmwares.
Burning some FETs wouldn't be a problem as long as it happens on the bench, but I really want to make it work, or at least understand why it will not be possible.
cecca
 
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Re: 5s + brake = magic smoke?

Postby chschmid » Tue Jun 24, 2014 6:29 pm

I would wait for ESC32 V3. Comming soon.

Cheers
Christof
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Re: 5s + brake = magic smoke?

Postby cecca » Tue Jun 24, 2014 6:43 pm

Can you explain why V2 wouldn't be able to do it?
cecca
 
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Re: 5s + brake = magic smoke?

Postby chschmid » Tue Jun 24, 2014 7:02 pm

No I can not. Sry.
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Re: 5s + brake = magic smoke?

Postby cecca » Tue Jun 24, 2014 7:34 pm

Well, I guess you can't tell me why should I buy V3 either...
cecca
 
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Re: 5s + brake = magic smoke?

Postby cecca » Tue Jun 24, 2014 7:41 pm

Is the problem related to dead time between fet off and fet on? Is possible to increase it?
Or is Vds(max) of the fets which is just too low? Or maybe something else...
cecca
 
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Re: 5s + brake = magic smoke?

Postby JussiH » Tue Jun 24, 2014 7:55 pm

Bill will be able to give more detailed explanations and possibly point in the right direction if you want to venture further with FET braking.

AFAIK, part of the problem is that the V2 ESC32 hardware is not ideally suited to do Active freewheeling. Likely something could be done in SW, but as far I know, it was never explored in depth after it was seen that blown fets was the prevalent result...not many people like blowing out their ESC´s to test a experimental feature so it was one of those things that got left behind in a fastmoving project with limited ressources... ;)

A vastly improved Version3 ESC32 is in team testing and shows extremely promising results for Active freewheeling among many other things.
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Re: 5s + brake = magic smoke?

Postby cecca » Wed Jun 25, 2014 2:18 pm

Thank you, hope to hear more from Bill soon :)
cecca
 
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