I was using the Arduino Motor Shield, and somehow it fried my voltage regulator. I could only power my UNO via the USB port. So I bought a package of AMS1117 5.0 Voltage regulators. I desoldered the old regulator, and soldered a new one.
The bord is now working, but the power consumption of the UNO is around 195mA when I'm powering the board using the 5V pin ?! The newly installed voltage regulator gets hot in like 15 seconds (Have no idea why, since i'm supplying the bord using the 5V pin). Same goes if I power the UNO using the USB port. The regulator gets superhot.
If I power the UNO using the Vin pin, it works fine.
Any tips re troubleshooting ? What could be the problem ? Can I fix this issue ?
Thanks for the tips <3
edit:
195mA in idle mode, nothing is attached to the UNO
It my UNO is to most common regular standard UNO R3, bought from China.
Here is the schematic. I can't remove the ATmega328P since it's embedded to the board (by that I mean it doesn't have a socket). Other board from the same supplyer works well.
The weird thing is that even when I power the UNO using the USB port, the voltage regulator gets hot.
edit: @westfw - yes, it was an AMS1117 5.0, 100%. The pins are identical.
It is a bit difficult to see anything from the schematic which could, be a single component failure, cause the overheating of the voltage regulator when the Uno is powered via the USB socket. The most plausible explanation would be a different regulator pin out which you have already ruled out.
Some Uno clones have a completely different power circuit so it is not clear how relevant the standard schematic is.
What were the symptoms which caused you to change the regulator ?
Can you measure the voltage of the 3.3 volts pin when the device is powered via the USB socket ?
195 mA (at 5 volts) is equivalent to a 25 Ohm resistor.
Most common UNO from China is not UNO R3 and it has usually CH340 instead ATmega16U2 as USB/serial transceiver, which is the most significant difference. Schematics is for UNO R3.
The weird thing is that even when I power the UNO using the USB port, the voltage regulator gets hot.
That IS weird because according to the schematic 5V is connected directly to the voltage regulator (as you'd expect) and that means people "back-power" it all the time and it shouldn't get hot.
Have you confirmed 5V is correct? Or maybe there was a spike that damaged the voltage regulator? Maybe from the motor? Have you checked to make sure the voltage regulator is still working?
Looking at the voltage regulator datasheet there is a "hint" that a shorted input could damage it if it's back-powered. Make sure there isn't a short on the regulator input (Vin), such as a shorted input capacitor* which should be 'PC1'.
...I once ran-across a situation where an expensive lab-bench type power supply had voltage spike when turned-on that was killing boards (not an Arduino). That was unexpected from a reputable company!
P.S.
Thinking about it... I'm suspecting a shorted capacitor... The original regulator may have been OK...
"What were the symptoms which caused you to change the regulator ?"
I made a robot а few months ago, it's powered by a 12V battery from my drilling machine. 12V goes to the Motor Shield. Since I have the jumper wires in place, the UNO is feed with voltage directly from the Motor Shield. It used to work great, but a month ago I saw white smoke coming out of the system. The shift register on the shield was not working, so when I replaced it, everithing worked well, exept the voltage regulator - I could only power the UNO via USB or directly 5V.
It worked well, and 2 days ago I saw white smoke again , and since then I have this problem.
When powered via USB, the voltage on the 5V pin is 5.1V, and the 3V3 is also correct, but again - the voltage regulator gets very hot. I guess i would see white smoke if i left it the UNO on for 2-3 minutes.
8.2V to the VIN pin. Since today it's fried as well
"Or maybe there was a spike that damaged the voltage regulator?" - maybe, but the motor driver on the motor shield has flyback diodes.
I mean - if it's too hard to identify the problem, i can discard the UNO and buy I new one. But there is noting to learn in that case. Also i dont want to fry another UNO by putting it in the same system.
The schematic here appears to be a better match for your Uno clone:
It has the CH340 USB chip, the unique break out pad set for power, I2C and serial and a 4 pad breakout to the CH340G.
But, again, it is difficult to see a single component failure which would cause the 5 volt regulator to get hot, that is apart from the regulator itself, when the board is powered via the USB socket at 5 volts.
It sounds now, like it is too late, but i would have unsoldered the 5v regulator again and check what still works when the board is powered via USB.
I have unsoldered the voltage regulator, and the UNO works fine when powered via USB.
When I power it using the 5V pin - the UNO is consuming 15mA, so everithing looks ok.
I might solder another VR and see if that will fix the problem, or I will find another function for this "VR-less" UNO
Thanks for the assistance, I appreciate it very much <3
, and since then I have this problem.
