Newly soldered VESC won't power ON

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rmrf
Posts: 13
Joined: 11 Apr 2016, 06:17

Newly soldered VESC won't power ON

Postby rmrf » 01 May 2016, 17:09

I just soldered my first VESC. Bought boards at oshpark. Components at Mouser. HW 4.10. Successfully uploaded bootloader with ST-Link and "make upload" (got "verified ok" message in the terminal), then disconnected 6pin cable and connected VESC to the battery 5S LiPo (18.5V). Unfortunately it does not show any signs of life. No LEDs are blinking. How do I diagnose the problem? Where do I start?

Front:
Image

Back:
Image

CR2 files:
https://dl.dropboxusercontent.com/u/214 ... t/back.CR2
https://dl.dropboxusercontent.com/u/214 ... /front.CR2

Florian
Posts: 4
Joined: 01 May 2016, 17:46
Location: Munich, Germany

Re: Newly soldered VESC won't power ON

Postby Florian » 01 May 2016, 18:07

Hi,

I am by no means a Vesc expert (look at my number of posts, i have only soldered one vesc myself).

How did you power your Vesc while flashing the bootloader? Can you still connect to the microprocessor with the programmer?
If you did power the processor via the usb port while programming, I think you should disconnect/remove the solder bridge (R6 in version4.12) before connecting a battery.
Can you test the current draw of your vesc? IMHO It is a good idea to power your vesc of a lab power supply for the first time. A Voltage of 12V and a current limit of 100mA should be fine. (My VESC draws about 50mA @ 12V with nothing connected. That's how I discovered my badly soldered drv8302.)

As a quick glimpse at your pcb doesn't show any obvious faults (exept for maybe optical, uncleaned flux residues ;) ) i would test the following:
- try if programming still works ( i had to power my vesc with the usb hack above to be able to program it without the battery connected, but i use a stm32f3discovery as programmer )
- try powering it with usb (could be dangerous for usb power source)
- try powering it with current limited lab power supply and measure voltage across D5 (should be about 5V). If it isn't the voltage converter in your drv8302 doesn't do it's job.

With the limited information you have written I can't think of a specific fault, but as mentioned I'm no vesc expert.

Good luck

PS(Edit): Your blue power led was lit while programming? It should light up if there is 5V power on the pcb. But not if you did program with only 3.3V present. You can check that your leds are soldered in the correct orientation with a multimeter in diode mode.
I don't know your tools/knowledge so I'm guessing here.

rmrf
Posts: 13
Joined: 11 Apr 2016, 06:17

Re: Newly soldered VESC won't power ON

Postby rmrf » 01 May 2016, 18:24

Florian wrote:How did you power your Vesc while flashing the bootloader?

I used 6-pin header and ST-Link V2 programmer bought from ebay. No other power source connected while programming.
Florian wrote: Can you still connect to the microprocessor with the programmer?

Yes, but when I try to reupload ("make upload" again), I get "write algorithm aborted by target". Maybe you can upload bootloader only once?
Florian wrote:Can you test the current draw of your vesc? IMHO It is a good idea to power your vesc of a lab power supply for the first time. A Voltage of 12V and a current limit of 100mA should be fine. (My VESC draws about 50mA @ 12V with nothing connected. That's how I discovered my badly soldered drv8302.)

Good point, I will do this when I get back to the lab. I did a mistake and tried with LiPo 5S right away.

Florian wrote:- try powering it with current limited lab power supply and measure voltage across D5 (should be about 5V). If it isn't the voltage converter in your drv8302 doesn't do it's job.

I just tried with LiPo battery again, and multimeter at home. Voltage across D5 is 0.
Florian wrote:PS(Edit): Your blue power led was lit while programming? It should light up if there is 5V power on the pcb.

That's weird. My blue led was flashing, but I used only 3.3V from the ST-Link.

P.S. I never soldered R6, but good to know about this USB hack :)

Florian
Posts: 4
Joined: 01 May 2016, 17:46
Location: Munich, Germany

Re: Newly soldered VESC won't power ON

Postby Florian » 01 May 2016, 18:37

I just tried with LiPo battery again, and multimeter at home. Voltage across D5 is 0.

So there is no 5V power and no input to the 3.3V linear regulator. I would trace the power from the input to the 5V as a next step.
The buck converter around L1, D4 and the drv8302 should be working. Looking at the schematic in Kicad helps a lot. You find connections to test as next step.

rmrf
Posts: 13
Joined: 11 Apr 2016, 06:17

Re: Newly soldered VESC won't power ON

Postby rmrf » 01 May 2016, 19:41

Florian wrote:The buck converter around L1, D4 and the drv8302 should be working. Looking at the schematic in Kicad helps a lot. You find connections to test as next step.

I am looking at this part of the schematic
Image
I measured voltage across several things:
Voltage across C27 = 6.1V
one side of C27 to GND = 9.3V
another side of C27 to GND = 2.2V
one side of L1 to GND = 1.75V
another side of L1 to GND = 0V

The problem is that I lack the knowledge to understand how to interpret these results.

While I did the measurments, blue LED started to blink randomly (mostly on, 5-10% random glow off blink)
I measured voltage across D5 again - and it was jumping ardound 2.5 - 3.3V and I beleive I saw some smoke near D5, plugged the battery off quickly. :?

Florian
Posts: 4
Joined: 01 May 2016, 17:46
Location: Munich, Germany

Re: Newly soldered VESC won't power ON

Postby Florian » 01 May 2016, 20:48

I think my explanation was a little rough, i thought about checking the connections with the ohmmeter and a completly unpowered Vesc. I thought that a bad solder joint or a missing connection could lead to your fault. That's why my idea was to compare the real pcb with the schematic and the pcb in Kicad.

The marked circut converts your input voltage to 5V in normal operation. But if the feedback somehow fails the voltage after L1 (5V the C33 side of L1) gets out of range. D5 is a TVS diode, it protects your circut if your 5V power is actually too high. The voltage fluctuations you saw are probably from the drv8302 trying to boost the 5V because of wrong feedback. Another explanation is that your drv8302 tries to raise the 5V while D5 consumes as much current as necessary to keep the 5V safe. Thats why D5 gets hot and eventually burns up when your input current is not limited.
I had the same fault with my Vesc after the first assembly. I didn't mention it before, because your output at the 5V rail was zero ...

What I think that happened:
When you measured the voltages in the circut you did put some pressure on the drv8302. That improved the ground pad connection on the drv8302 a bit, but not completly. (The ground pad is the pad under the chip, which is hard to solder by hand. It's not available at a normal pin.) Now the scenario above happened.
If your Diode D5 is still in good condition, try to resolder the drv8302. Pay attention to the pad. I had to resolder mine and it solved the problem. This is a pretty common problem if you read the posts in this hardware problem subforum. I shielded all of the other components with multiple layers of heat resistant tape from the hot air, used an awful lot of flux and cleand the whole mess afterwards. Look at the tutorial on drv soldering in the Vesc blog post: http://vedder.se/2015/01/vesc-open-source-esc/
And try to use a current limited power supply for any first run if there is any possibilty to do so, it prevents things from going unfixable ;)

Here is the connection of D5:
tvs.PNG
tvs.PNG (31.61 KiB) Viewed 5237 times


If you are interested in unerstanding the circut, read some lines here: https://en.wikipedia.org/wiki/Buck_converter

rmrf
Posts: 13
Joined: 11 Apr 2016, 06:17

Re: Newly soldered VESC won't power ON

Postby rmrf » 13 Jun 2016, 17:09

Thanks @Florian, for lots of useful information, now I am much more careful soldering my second VESC. My first one I decided to send to @xlv repair service in Germany. It turned out that The Buck Regulator Pins of the DRV werent soldered correctly, and STM32 was burned down. Under it the PCB was a bit darkened from heat.

Unfortunately I also have problems with my second VESC. It can't be detected with BLDC-Tool over USB after successfull firmware upload via ST-Link. When I power on the VESC with a lab power supply 12V, it draws about 60mA which is good. Voltage over D5 is 5.1V, also seems good. Red led blinks 3 times and then green led stays on. Seems like the problem described here viewtopic.php?f=7&t=157 but no solution. I will try to investigate further.

rew
Posts: 940
Joined: 25 Mar 2016, 12:29
Location: Delft, Netherlands.

Re: Newly soldered VESC won't power ON

Postby rew » 14 Jun 2016, 06:43

rmrf wrote: When I power on the VESC with a lab power supply 12V, it draws about 60mA which is good.
Sounds like a bit much to me....

I'd double check the USB connections if the CPU runs and blinks.

rmrf
Posts: 13
Joined: 11 Apr 2016, 06:17

Re: Newly soldered VESC won't power ON

Postby rmrf » 14 Jun 2016, 19:48

Thank you @rew! You were right, it was USB connection problem!

I took a multimeter and started checking if there was a short between USB connector pins. And it was! It is very hard to see but under microscope it is clearly visible.
Image

I removed it but now the multimeter was still beeping like it is a short but with a small delay :( I measured resistance between the usb pins and it was 45Ω between the pins where I just removed the bridge (it was 0Ω with a bridge). So I decided to go further. I found that this is USB mini B and here is pinout:

Image

The problematic pins were 2-3. I opened VESC project in KiCAD and found that pins 2-3 go to R103 and R104 resistors and then to STM32 pins USB_DP and USB_DM.

Image

Then I double clicked STM32 module and it showed that USB_DM and USB_DP are PA11 and PA12 on STM32 chip (or 44 and 45).

Image

Then I found pdf specification of STM32 on mouser and found where pins 44 and 45 are located

Image

I measured resistance between 45 and 44 and it was 0Ω! Now I understood why resistance between 2-3 usb was 45, it was measured through R103 and R104 resistors which got connected in series by shorted STM pins. I removed the short with a solder wick.

(on the photo the solder wick is on the different side from 44 and 45 pins, I could not make a photo while actually doing work because I need to hold my phone in one hand :) )
Image

I took a thin strand from a copper wire and attached it to multimeter probes. This way I could examine shorts between neighbour pins. I actually found one more short on STM and removed it! I could not see this with my eyes even under the microscope.

Image

Then I moved to the DRV and checked all neighbour pins as well I found 2 places where pins were shorted! But it actually turned out that this is by design. Pins 54-53 and 51-50 are connected to each other
Image


My VESC can now be detected by BLDC-tool. I'm very happy that I could find the problem even with my basic skills. This is amazing feeling :D Yeeee-haaa!

rew
Posts: 940
Joined: 25 Mar 2016, 12:29
Location: Delft, Netherlands.

Re: Newly soldered VESC won't power ON

Postby rew » 15 Jun 2016, 06:30

Good work! :-)

Rereading part of the thread to figure out where I left off, the 100mA limit is fine for "basic testing". Then I usually increase the current limit to say 0.5A and then run a motor at 2A for a while to check that it works....


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