I think my Pi either just over heated, burned out, or shorted out, please help..

stoo

@riverstorm As I understand it, it never returns to the original resistance but it can get close enough that using it "normally" won't cause the polyfuse to heat up to the point where it trips again. Plus, keeping the Pi cool is a good idea generally :P

I've never had a power issue with my RPi3, but then I've always used the official PSU.

stephensmattlee

I also suggest giving the official power adapter a go, I had the lightning bolt and severe slowdowns when playing games using the CanaKit power adapter that came with my Pi but all problems went away when I tried the official adapter instead. Hope you manage to get yours working properly again

spruce_m00se

I guess I will have to read up on polyfuses, but it makes no sense to me that a fuse would trip when the supply voltage goes too low. In theory I know that something using a fixed amount of watts would draw more amps at a lower voltage, but if a power supply cant supply enough juice at 5V then it can supply it at a lower voltage either.

Either way, the Pi that I had which tripped, has worked flawlessly for six months since, so im not worried, and if it got worse, I guess id replace the polyfuse if the concencus is that it is the issue.

stoo

@spruce_m00se "but if a power supply cant supply enough juice at 5V then it can supply it at a lower voltage either."

I believe the undervoltage protection on the Pi is mostly there because the Pi quickly becomes unstable when faced with a (relatively small) voltage loss caused by excessive load. It's more about being able to trace crashing or data corruption problems to a power fault than fear that the Pi will go up in blue smoke because someone used a cheap PSU.

I think there are separate fuses on the USB ports to prevent people from killing their Pi while attempting to power their desk fans through them :P

I may be wrong about the above, but that's what I gather from reading forum posts.

Clyde

@stoo said in I think my Pi either just over heated, burned out, or shorted out, please help..:

I think there are separate fuses on the USB ports to prevent people from killing their Pi while attempting to power their desk fans through them :P

What?! :O *quickly removes the desk fan and refridgerator from his Pi's usb ports*

stoo

@clyde lol, yeah I found my GE752 motor was a bit much for the Pi to handle.

spruce_m00se

@stoo I understand that, but Ive never seen a "fuse" that blows when the voltage is too low. Normally they are for high voltage. It makes no sense to me how a fuse can blow or trip from low voltage.

markwkidd

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markwkidd

@spruce_m00se said in I think my Pi either just over heated, burned out, or shorted out, please help..:

@stoo I understand that, but Ive never seen a "fuse" that blows when the voltage is too low. Normally they are for high voltage. It makes no sense to me how a fuse can blow or trip from low voltage.

"Some Pi models have an onboard chip which detects a low voltage. This is used to drive the power LED on some Pi models." https://raspberrypi.stackexchange.com/questions/60593/how-raspbian-detects-under-voltage

Riverstorm

@spruce_m00se said in I think my Pi either just over heated, burned out, or shorted out, please help..:

@stoo I understand that, but Ive never seen a "fuse" that blows when the voltage is too low. Normally they are for high voltage. It makes no sense to me how a fuse can blow or trip from low voltage.

I think what he's saying is the fuse shouldn't trip from low voltage. It does give you a warning indicator (via lightning bolt) under a certain voltage but I don't believe the Pi shuts down or trips when the voltage value goes from high (normal) to low (undervoltage).

I think you may see other issues like corruption, reboots, powering down, etc. due to under-voltage.

stoo

@spruce_m00se To my limited understanding, when you overload a switched-mode power supply the voltage will drop. The components it is powering (the Pi in this case) will then try to draw more current to meet their power demands.

Certain components will be unable to handle an increase in current, hence the overcurrent protection. In this case the overcurrent is caused by low voltage, which is caused by a PSU that is not capable of supplying enough power. Polyfuses trip by heating up when the current exceeds a certain value.

I am soooo not an electrical engineer and I know very little about electronics, so ~~I'm sure there are many factors here I'm not considering~~ this is probably just plain wrong. Someone with more knowledge should feel free to ~~jump in~~ correct me in the harshest terms. :P

I should probably just remove this reply as the more I read it, the less sense it makes. I think I'm conflating two separate conditions.

spruce_m00se

@stoo My understanding of ohms law and electronics is that you take votlage and amps to get wattage, and in reality the fuse can pass a certain amount of watts.

That doesnt change as far as I know, essentially if you have a 10a 12v fuse you can bung 24v 5a through it, or 6v 20a.

spruce_m00se

However , thinking about it a bit more, the higher the voltage and lower the amps, the less the resistance of the cable/fuse causes issues with heating etc, and lower voltage and amps cause higher heating due to resistance,

since polyfuses (according to wikipedia) "trip" from the heat build up during use. The lower voltage and higher amperage would heat it more, thus making it "trip"