D5 was not mounted on DIYGadgets pcb when powering VESC.. is it dead now?

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dlankvel
Posts: 5
Joined: 08 Mar 2017, 10:45
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D5 was not mounted on DIYGadgets pcb when powering VESC.. is it dead now?

Postby dlankvel » 08 Mar 2017, 11:05

Dear all,

I ordered three VESC partly assembled PCB from DIYGadgets (http://www.diygadget.com/vesc-bldc-open ... mbled.html) Had a friend (who has a PCB prototyping business) order components and help me solder the STM32, DRV, FET's , shunt's and Cap. Rechecked connections under a microscope at work and corrected (patched) some flaws on the soldering of the DRV chip (some the PCB pads came loose during prep for soldering.. poor quality pcb :-( )

Now I hooked up my VESC to a 24V PSU and try to program my STM with a JFlash programmer over SWD and it fails. The J-link probe is able to connect to the STM but programming/erasing fails. JFlash reports a supply voltage of only 2.27V... so I start searching the web for answers for this low VCC and end up in this thread: viewtopic.php?t=134 , where user 'rew' reports the next:

>D5 is the protection diode that prevents the 5V signal from going MUCH over 5V. So if D5 was not there, everything would have been broken by too high >voltage on the 5V line. (the 3.3V regulator would blow, giving too much on 3.3V which in turn would blow the STM and the maybe the DRV too...).

So I check the D5 ,that is supposed to be mounted coming from DIYgadgets, and it's not mounted !!!

So the general question now.... did I blow my components by hooking up to the 24V PSU without the D5 mounted ?? How can I check if they're still OK?

Regards and thanks for your time.

arvidb
Posts: 234
Joined: 26 Dec 2015, 14:38
Location: Sweden, Stockholm
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Re: D5 was not mounted on DIYGadgets pcb when powering VESC.. is it dead now?

Postby arvidb » 08 Mar 2017, 12:57

D5 is an additional overvoltage protection for the 5V rail, so if the 5 V switching regulator in the DRV8302 and its peripheral components (L1, D4, C33, C27, R17, R18, ...) were correctly mounted, the lack of D5 should not have blown anything up.

Two things you can do:

1) Measure the voltage over C33. It should be close to 5 V.
2) Measure the voltage over C25. It should be close to 3.3 V.

If they are both correct, then your on-board power regulators are working correctly.

dlankvel
Posts: 5
Joined: 08 Mar 2017, 10:45
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Re: D5 was not mounted on DIYGadgets pcb when powering VESC.. is it dead now?

Postby dlankvel » 08 Mar 2017, 13:31

Thank you for your answer!...Although it doesn't help me anymore because I screwed up during measurements, shorted out and blew a cap of the regulator. Replaced the cap by taking it of one of the other boards and then blowing the drv completely. It was partially blown anyway because it didn't deliver the 5V. That was what I was trying to find out..

Anyway.. Just before it al went haywire I hooked up the VESC to the 3.3V supply of an Arduino and was able to program the STM..so that at least was solved for as long as it lasted :-(

I am going to discard this board because I do not trust the components anymore after the short.. Well.. Maybe the FET's and some caps can be salvaged..

Back to the drawing board...

Regards,

rew
Posts: 943
Joined: 25 Mar 2016, 12:29
Location: Delft, Netherlands.
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Re: D5 was not mounted on DIYGadgets pcb when powering VESC.. is it dead now?

Postby rew » 08 Mar 2017, 23:50

Read carefully what I wrote in the other thread and why that diode is there....

The ground pad of the DRV chip is difficult to solder, so people hope it isn't necessary. But it is.

dlankvel
Posts: 5
Joined: 08 Mar 2017, 10:45
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Re: D5 was not mounted on DIYGadgets pcb when powering VESC.. is it dead now?

Postby dlankvel » 09 Mar 2017, 06:57

Thank you for your response 'rew'..

As for the ground pad... The DRV ground pad was filled with solder before placing it. So it was on top of some solder and sunk in when using the hot air soldering station. So I "assume" it was making good contact, then again.. It might not have been enough solder to fill the space under the DRV when heated uniformly... How to check this connection? Measure resistance between AGRD on the DRV (pin28) and voltage supply pad 5?

Regards,

rew
Posts: 943
Joined: 25 Mar 2016, 12:29
Location: Delft, Netherlands.
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Re: D5 was not mounted on DIYGadgets pcb when powering VESC.. is it dead now?

Postby rew » 09 Mar 2017, 08:48

If that's how you did it, the ground of the DRV should've been OK.

dlankvel
Posts: 5
Joined: 08 Mar 2017, 10:45
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Re: D5 was not mounted on DIYGadgets pcb when powering VESC.. is it dead now?

Postby dlankvel » 09 Mar 2017, 10:51

Sorry this short dutch 1:1 to all non dutch readers..

Btw rew, we zitten een stuk dichter bij elkaar dan ik had aangenomen.. Delft <-> Eindhoven.. :-D


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