I need some fresh eyes

[jonhllstrm]

Hey guys, i am trying to figure out why this thing isn't working. I've had some boards made, and honestly if I have to make more, it's not a problem. Theoretically this should all be fine, but i can't seem to figure out why it isn't.
I've got the schematic from eagle and board file if that is gonna help. I managed to get a less complicated board working fine, and ill try and get schematics for the components and the circuits i used. It's gonna have to be later, as it's 3am here in australia. Any help is appreciated as i've been trying to get it working the last hour or so...

https://www.dropbox.com/sh/v6hi49gvwqbtv5q/AADBXZ-u1fhxDpK1UU_JYDGpa?dl=0
and those are the files

 

[BobK]

Hi, and welcome to E.P.

"Isn't working" is a pretty vague description of a problem. Can you be more specific?

And the link you posted is for a site one must subscribe to. We are not going to subscribe to a random site to look at you files.

Sorry to be so negative, but your post does not include anything that would allow us to help you.

Bob

 

[davenn]

Hey guys, i am trying to figure out why this thing isn't working. I've had some boards made, and honestly if I have to make more, it's not a problem. Theoretically this should all be fine, but i can't seem to figure out why it isn't.
I've got the schematic from eagle and board file if that is gonna help. I managed to get a less complicated board working fine, and ill try and get schematics for the components and the circuits i used. It's gonna have to be later, as it's 3am here in australia. Any help is appreciated as i've been trying to get it working the last hour or so...

Hi, and welcome to E.P.

"Isn't working" is a pretty vague description of a problem. Can you be more specific?

And the link you posted is for a site one must subscribe to. We are not going to subscribe to a random site to look at you files.

Sorry to be so negative, but your post does not include anything that would allow us to help you.

Bob

Agree with Bob

please upload graphics files to here with a max of 900 pixels on the long side and a max of 100kb per file and ensure they are in a standard format ... GIF, JPG
for any text just copy and past into your thread along with the images


Dave

 

[jonhllstrm]

Thanks for responding so quick guys, and i'm sorry about that. I shared the files publicly on dropbox, so i have no idea why youd have to sign up. Me being awake for 40 hours straight did not help. I've attached the files to the post, but they are a pretty horrible resolution to keep to the max size...

With the previous revision of board, i have had no problems just assembling and plugging in. With the new boards, which came in the other day, i feel the problem may be the way i've traced the board... But i have no idea where to start troubleshooting, as they are mostly smd components, and i've been scrapping parts of circuits together.

 

[jonhllstrm]

There doesn't seem to be any power getting to the board either, and it should theoretically be working when i just remove the lipo charging circuit.. as that is the only change besides mic bias in the new boards

 

[(*steve*)]

you say there's no power getting to the board. Have you measured the power supply rails?

 

[jonhllstrm]

Hey steve, thanks for the reply,

I realised I didn't really explain what this thing is;

It's a Bluetooth audio module, with an lm324 and mcp73831 lipo charging circuit in it. When i plugged in the battery (probably the wrong way around), the mcp chip started burning. This was only for half a second, and then i cut the chip off the board (cause i have 300 of them, and if it was burning, i was probably gonna have to replace it anyway).

As for the base circuit, which i haven't changed since the previous revision, when the lipo is attached, the led indicator in the bottom left should start flashing. This doesn't happen, and i think maybe the power is getting drawn away from the bk chip somehow. i measured the 3v out pin on the chip, and it was outputting 250mv.

I just no idea how this is happening, as i have some base knowledge of electronic circuits and I can troubleshoot, but i think i've gotten to the stage where it's just out of my league, and in designing this circuit, i've made it too hard for myself to know if something is going wrong.

 

[davenn]

As for the base circuit, which i haven't changed since the previous revision, when the lipo is attached, the led indicator in the bottom left should start flashing. This doesn't happen, and i think maybe the power is getting drawn away from the bk chip somehow. i measured the 3v out pin on the chip, and it was outputting 250mv.

I just no idea how this is happening, as i have some base knowledge of electronic circuits and I can troubleshoot, but i think i've gotten to the stage where it's just out of my league, and in designing this circuit, i've made it too hard for myself to know if something is going wrong.

well for starters
there's probably much more damaged by the reverse voltage than just that mcp chip
you can count on replacing the LM324 and any other semi conductors as well



Dave

 

[jonhllstrm]

Hey Dave,
I'm sure I will, but I have 3 of the boards unpopulated, so if need be I can just chuck the one I've screwed up and populate a new one. The Bluetooth module itself doesn't seem to suffer, and i assume a few Diodes are involved. The lm and MCP are the only individual ics.
Theres also the possibility it was just the MCP chip and it burnt out everything else. I got these in bulk from China. $30 for 100 or so

 

[davenn]

The Bluetooth module itself doesn't seem to suffer,

how can you assume that, unless it wasn't plugged in ? where does the BT module plug in ?
what is that device in the top left corner of your first diagram ... the BK8000 ?, it would have got reverse voltage as well

 

[jonhllstrm]

Well, these are cheap modules from China again, but I've had them for a while before I got the boards, so I've tested them alot. I've put power supplies in the wrong way around many times, and it doesn't seem to have any problems with it. My assumption is they just have a diode to prevent any damage.

As it doesn't have too much documentation, there is not much I can say about it, as I also had to make my own eagle library for it.

But as I said, I've gotten the previous revision of the board working absolutely fine.

 

[Harald Kapp]

But as I said, I've gotten the previous revision of the board working absolutely fine.

Compare the two revisions in schematic and layout, trace by trace to find any differences. Then analyze the differences. You must have had a reason for a new revision, why would you otherwise have changed away from a revision that was working fine?

 

[jonhllstrm]

Hey mate,
If I hadn't done that already, I wouldn't be asking for help. The previous revision doesn't have a lipo charger inbuilt.

I've been looking at this thing for a couple of days now, and i just can't find any difference and i still have no idea why it isn't working

 

[davenn]

Well, these are cheap modules from China again, but I've had them for a while before I got the boards, so I've tested them alot. I've put power supplies in the wrong way around many times, and it doesn't seem to have any problems with it. My assumption is they just have a diode to prevent any damage.

As it doesn't have too much documentation, there is not much I can say about it, as I also had to make my own eagle library for it.

But as I said, I've gotten the previous revision of the board working absolutely fine.

tis bad to make assumptions like that

I will make the assumption that you have killed something as has been suggested earlier and until you do the proper tests and checks
And until you do so, we are all just guessing on how else to help you

You have to assume you have killed ALL sensitive parts and work from that standpoint


D

 

[Harald Kapp]

The previous revision doesn't have a lipo charger inbuilt.

• Disconnect the charger (SW2 in pos. 2-3), Connect the power supply you used for the working modules instead. This verifies the 'original' circuit is still working properly.
• Check the circuit around the MCP73831. I think it is wired incorrectly. Vss should be connected to GND, but is connected to GND only via R17 and LED3.
  Status output STAT is connected to pin Vss.
  This is not logical and in contradiction to the datasheet.

 

[Ratch]

Hey guys, i am trying to figure out why this thing isn't working. I've had some boards made, and honestly if I have to make more, it's not a problem. Theoretically this should all be fine, but i can't seem to figure out why it isn't.
I've got the schematic from eagle and board file if that is gonna help. I managed to get a less complicated board working fine, and ill try and get schematics for the components and the circuits i used. It's gonna have to be later, as it's 3am here in australia. Any help is appreciated as i've been trying to get it working the last hour or so...

https://www.dropbox.com/sh/v6hi49gvwqbtv5q/AADBXZ-u1fhxDpK1UU_JYDGpa?dl=0
and those are the files

Did you say fresh eyes, or refreshing eyes? Here is a refreshing pair of eyes.


And here is another one.


Ratch

 

[davenn]

lots of good guidance has been given earlier in the thread
it's now up to the OP to take that advice

 

[jonhllstrm]

Thanks davenn, and Harald; that is exactly what i needed to hear, after all this time, and i only just realised i was completely overlooking the stat pin on the mcp.

And Ratch, those are some really refreshing eyes!!

I'm sorry about all the confusion at the start, but I thank each and every one of you for taking the time to write a response!