Why I fried my uno board

I fried my uno board it seems because I can't upload anything to it now.

I was running 4 continuous rotation servos off the 5V pin of the board.

I am a complete beginner and just want to clarify two things.

1: Should I have a separate power supply for each servo or just a single separate supply for all 4 ?

2: My beginner kit came with a 9V battery pack containing 6AA batteries. It plugs into the side of the uno. Is this supply fine to run the uno?

Thanks for your help.

A separate supply that can handle all four servos is fine… as the arduino shouldn’t be affected in terms of what arrangement we have for external supplies.

Oh … yep… ‘powering’ servos from the 5V pin can certainly damage the arduino. Make sure to read up on power output specifications of power sources before connecting loads to the source. Eg. find out how much current the supply can safely output first.

When you mention running servos off the 5V pin of the arduino… I assume you mean powering those servos from the 5V pin. Yeah…better not do that.

Powering the arduino with 9V batteries is fine.

Southpark: When you mention running servos off the 5V pin of the arduino..... I assume you mean powering those servos from the 5V pin. Yeah.....better not do that.

As far as I know, it's not necessarily a bad thing to power components from the 5v pin. From what I've found online, at least on the MEGA, the 5V pin can safely handle 500mA of current, so if all 4 of his motors together even at their stall currents are below that, it shouldn't be an issue.

If you are taking 500mA from the 5V pin and driving lots of IO from the Mega and also sourcing 3.3V current, you will likely put the 5V regulator into thermal overload - it's only rated for 800mA, and will likely not do that unless the barrel jack is on 7.5V. If you are powering from USB, the 500mA PTC polyfuse may blow also with 500mA from the 5V power header.

I just measured my Uno using the diode setting on my multimeter, no power connected to the device:

Round external power (+) connector to Vin pin (-): 0,8 V (protective diode) Vin (+) to 5 V (-): 1,2 V (voltage regulator) I did not measure on the USB connector.

If those are different, you have fried the voltage regulator.

If you have about the same values as I have, I think it's the CPU. To avoid this, you must not connect motors directly to the pins. You can use open collector circuits or driver chips. (Also use an external power supply for the motors).

Also I just stumbled on this guide: http://www.open-electronics.org/the-power-of-arduino-this-unknown/

7eggert: I just measured my Uno using the diode setting on my multimeter, no power connected to the device:

Round external power (+) connector to Vin pin (-): 0,8 V (protective diode) Vin (+) to 5 V (-): 1,2 V (voltage regulator) I did not measure on the USB connector.

How come 1.2 V when no power to the arduino board?

Because a multimeter set to the diode setting displays the measurement in volts. If you are actually measuring a diode, it will be the forward voltage drop of the diode.

MorganS: Because a multimeter set to the diode setting displays the measurement in volts. If you are actually measuring a diode, it will be the forward voltage drop of the diode.

Oh yeah.... thanks morganS, just noticed the 'on diode setting' thing...... the 'diode testing feature'.

@bbqbrett, one day before starting this thread, you started a thread in another section of these forums asking about powering your 4 servos from the 5V rail:- Wiring advice for control of 4 continuous rotation servos You said "I'm worried of potentially frying the circuitry.", and you were told not to power the servos from the Arduino 5V rail.

It was suggested that you "Buy a 5V/3A switchmode regulator walwart to power the servos"

Couldn't wait for one to arrive?

bbqbrett: 1: Should I have a separate power supply for each servo or just a single separate supply for all 4 ?

This was also answered in your first thread:- "......so you would need a 3A 5V supply to power 4 servos."

Perhaps in the future you should pay more attention to any advice that's given to you, and not waste people's time asking questions that you already know the answer to.