Circuit Shield dead board due to high input current

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Manicben
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Circuit Shield dead board due to high input current

Post by Manicben » Sat Aug 01, 2020 12:03 pm

Posting here as my emails to Kite are being rejected due to some SMTP authentication issue.

I've been using the Circuit Shield for just over a week now. My battery was low so I charged it for the first time. However I was careless and plugged it into my phone charger, which is rated at 5V 4A. I thought my phone charger was fine, as I've used it on other devices before, but I think it might've fried some components as after several hours of charging the CSh won't even turn on anymore.

The charging LED still comes on when plugged in, but none of the other LEDs come on. The CHRG LED dimly flickers when the battery and USB C cable are plugged in, but that's the only LED that lights up on the back of the board. I can also hear a faint high frequency (in terms of clicks per second, not pitch) clicking sound coming from the board when the battery is plugged in.

I understand its my fault for not being careful, but I was wondering if anything could be done to save the board? I've got a multimeter to hand in case anyone needs extra info.


PS: I'm not sure if the input current rating (or any other specs) is stated anywhere on the GitHub or forum thread. Might be something worth adding so that other users and I know what chargers are safe to use.

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kite
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Re: Circuit Shield dead board due to high input current

Post by kite » Sat Aug 01, 2020 12:48 pm

Hi, I'm hoping to have the email thing fixed pretty soon, it's been like this for a couple of days and I have web support on the case for it but they seem to be taking quite a while to get it resolved... anyway!

That's a real shame, the current rating shouldn't be an issue at all, however if the voltage were not set right from the charger (it's meant to do this automatically, and always default to 5v) that could cause this. There's a couple things that we can check to see maybe what happened, and hopefully based on the checks it SHOULD just be the battery charge IC that took itself out and saved everything else!

If you remove the board and everything that is attached to it:

1. Plug JUST the battery in, and using a multimeter can you measure the BACK of the battery connector contacts to read the battery voltage?
2. As above (#1), and turn the power switch to 'ON'. If you then flip the board over you should see a few test pads around the K logo and button pads, look for "VCC" (next to the version info) and "GND" (next to K logo) and measure these points
3. Turn OFF, remove battery, plug in the offending USB C cable, and on the top side just behind the USB C connector are two solder holes "PWR-IN" with a + and - .. measure the voltage here
4. As above (#3), measure the back of the battery connector. This may be a little tricker to read but what is MEANT to happen is it tried to detect the battery, and it does this by pulsing 4.2v into the connector.. so your multimeter if it has a quick enough response rate will see it jump up to about 4v and then back down to 0v .. i think once a second or so, worth a shot to see if you can detect that behaviour!

Manicben
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Re: Circuit Shield dead board due to high input current

Post by Manicben » Sat Aug 01, 2020 1:44 pm

Thanks for the quick reply, here are the requested voltages:

1 - 0.348V (battery prob out of juice at this point)
2 - 0.021V (even made sure my multimeter was reading correctly)
3 - 5.162V
4 - 0.042V constant, did not see the blip of 4.2V and I reckon my multimeter is responsive enough

Hope this clarifies where the issue lies. Cheers Kite!

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Re: Circuit Shield dead board due to high input current

Post by kite » Sun Aug 02, 2020 3:57 am

Hi,

Ok cool thanks, so based on that it seems like the issue is the charge IC (which also handles passing on the power to the regulators etc to power the device) as it isn't passing the power on, and not seeming to pass charge power too (makes sense as it's not charging). The battery MAY be a problem but can't tell until the actual charger is replaced! (as it's reading no power, but that could also be the battery protection chip disabling the output power, but if possible it would be good to try and charge it somehow.. if you have a variable voltage power supply, set it to 4.2v and limit the current to 500ma or so and apply it to the battery to 'wake it up' and let it charge for a while. The expectation is for it to pull 500mA and the voltage to slowly increase from like 3v upwards)

Next thing is to return the board to me and I will replace/repair as required. Seeing as my email is down i'll send you the details via discord for now!

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