3 of 3 people found this helpful
The raspberry pi does not have protection on the GPIO pins, so it is easy to short them out and damage the rPi. Sorry, but I know this from my own bad experience. After I shorted mine, I searched the web for fixes, but nothing worked. I hope you have better luck than me.
I have run a fan from the 5v pin (using a different rPi that I didn't damage) and it worked well, it ran for days and did not cause damage. But it was a very small fan. If you tried to run a larger fan, the rPi can't supply much power. The polyfuse protects the incoming power from the USB port, and not the pins.
5 of 5 people found this helpful
There is the remote chance you connected the fan to the wrong pins or at an angle which allowed the 5V supply to short over to the 3.3V line or to any one of the GPIO pins, or the ground line of the fan may have been inadvertently connected to a GPIO. Running a fan from the 5V GPIO line in itself is not a problem if properly connected, provided the current consumption is only modest.
As mp2100 states, and I too can vouch for, the Rapsberry Pi GPIO is fragile.
To troubleshoot, I would:
- Remove all connected accessories from the Raspberry Pi to minimise chance of faults in connected equipment causing the polyfuse to open.
- Wait some time to allow for the polyfuse to cool and re-form. Repeated tripping of polyfuses leads to degradation and earlier tripping.
- Power the board with a known good cable from another supply in case it is a power supply fault.
- Reimage the SD card in the off chance that an unexpected power-down corrupted it to the point it would not boot.
In terms of your measurements, you cannot directly measure the resistance across the polyfuse when the Raspberry Pi is powered - in circuit resistance measurements will not be accurate due to applied voltage and provide misleading results.
You are best to measure the 5V from the USB port side to see if the Pi is getting a full (approximately) 5V or if the polyfuse has opened (in which case it will read a lot less). Normally if the polyfuse has opened due to a drastic short, you will not get any power lights at all or maybe just a short "blink".
However, I suspect you might not have shorted the Raspberry Pi at all and instead may have killed it through Electrostatic Discharge (ESD). This can happen if your body develops a static charge and you touch a GPIO pin, thus discharging through the SoC and burning it through. This is why you shouldn't handle electronics unprotected, especially if you're around carpet or wearing wool or near a cat, etc ...
Firstly i want to say thank you (btw Everyone answer me)
I just wait for the polyfuse 4 days, but nothings happen. Still just red light, not blinking lighting properly.
I measure the voltage from PP7 and PP3(plus sd card case), get 4.91V, its has to be enough it think .
I try again the change software, try to boot from usb. Nothing worked. He says "Leave me with my loneliness".
Idk what can i do, its too expensive in my country and i need it in my project.
3 of 3 people found this helpful
Under normal circumstances, if you connect a fan to the 5V of the pi, that should work. The thing is, that this 5V is directly connected to several internal circuits on the pi. So if you apply an external "very different from 5V" voltage on it, things might break.
What I THINK may have happened is that you accidentally also unconnected the fan. The fan is an inductive component and will produce large voltages when you suddenly disconnect it from the power supply.
Even when only trying to make a connection you might accidentally make and then for a short while break the connection again. Contact bounce (normally refers to switches).
So if you do this again, only connect and disconnect when the power is not applied.
Good catch rew - I didn't even think of that, but definitely sounds like a plausible explanation as well! I guess whether that happens in practice will depend on whether the capacitors across the power rail and the regulation of the power supply can arrest or dampen the spikes sufficiently or not.
Hey i got a new raspi almost 1 week ago and yesterday I try to add cooler fan.
Fan was working 5V and think i can get from pinout. when i was a connect, raspi was restart.
I try again when its open ( Wish i shouldnt ) and bom, raspi gone. Its not working anymore. Only red light and nothings happening.
I think maybe it can be a short circuit and i measure with multimeter the polyfuse its 0 ohm without power, 0.13 Ohm on power.
I change the sd card and software.
But nothings happened.
What can i do ?