Arduino Uno Burning Out Issue

Hi,
I am currently creating an arduino project which makes use of a number of inputs and outputs. When testing a piece of code I wrote for this project with the inputs and outputs connected, the board stopped working and the microcontroller in the middle of the board caught alight. I was using a 12V 8A power supply for this test, I was using such a high amperage supply as I was planning on powering a peltier chip off the same supply however in this test the peltier was not included.

Attached are images of my code and the circuit I was running. (the relay outputs were not connected during this test)

As shown, I had 3 LEDs connected to pins 3, 4, and 5. 2 Switches connected to pins 11 and 10. I had all of the these pins connected to the same ground pin.

Some help to identify my problem would be much appreciated, I have probably made a silly mistake. Or is the power supply just too high of an amperage?(I have had the Peltier chip and Arduino running off this powersupply at the same time before and experienced no issues.)
Thanks
Ben

It is not possible to make out the circuit from the picture please draw the circuit and post a picture of it if you do not have any other method.

Weedpharma

In general terms, there is no such thing as a power supply being too high an amperage.

The voltage is the important thing and beyond that, the power supply and connecting wire must be able to supply AT LEAST SUFFICIENT Amperage, or a fire could ensue.

That being said, power supplies can also limit the current they supply deliberately to either protect the attached circuit, or protect the power supply itself.

So, if your circuit was drawing too much current such that the circuit burned out, the problem is in the circuit, not the power supply.

I haven't looked at your circuit, but if you don't have current limiting resistors, or all the current comes through the 1 ground pin and it is too high then yes, the magic smoke will escape.

edit: I have looked at the photo of your circuit and do not see any current limiting resistors on your LEDS. Using Ohms law, the current through each of the LEDs is:

I = V/R I = 12 / 0 I = infinite = possible fire

(this is an ideal case, but it highlights the problem). You need to limit the current through each LED to be somewhere around 10mA, assuming the LED has 0 resistance.

See here for the correct way to wire up an LED:

http://arduino.cc/en/Tutorial/Blink?from=Tutorial.BlinkingLED

Hi,

Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png or pdf?

Can you please post a copy of your sketch, using code tags? Please use code tags.. See section 7 http://forum.arduino.cc/index.php/topic,148850.0.html

Thanks..Tom....... :)

i dont think you understand how power works, to quote tom Everything runs on smoke, let the smoke out, it stops running......VK3DMK

If you actually see fire or smoke, it's more likely that something was over-voltaged or reverse-voltaged, which also leads to over-current, rather than simply "pulling" too much current from the device.

Where is the 12V connected? It should be connected ONLY to VIN or the barrel jack (so the power goes through the voltage regulator). If it's connected somewhere else, you may fry a component. The safest way to connect power is through the barrel jack unless you are running it off USB power or 5V.

It's also possible to indirectly over-voltage the device by connecting 12V to some component that's connected to the Arduino. (A properly connected transistor or MOSFET can safely go to 12V and to the Arduino.)

How did you power the board (12V on VIN)?

Burning an chip can be achieved by applying more than 5V to it, not normally by shorting pins to the regular GND or VCC.

arduinodlb: In general terms, there is no such thing as a power supply being too high an amperage.

The voltage is the important thing and beyond that, the power supply and connecting wire must be able to supply AT LEAST SUFFICIENT Amperage, or a fire could ensue.

That being said, power supplies can also limit the current they supply deliberately to either protect the attached circuit, or protect the power supply itself.

So, if your circuit was drawing too much current such that the circuit burned out, the problem is in the circuit, not the power supply.

I haven't looked at your circuit, but if you don't have current limiting resistors, or all the current comes through the 1 ground pin and it is too high then yes, the magic smoke will escape.

edit: I have looked at the photo of your circuit and do not see any current limiting resistors on your LEDS. Using Ohms law, the current through each of the LEDs is:

I = V/R I = 12 / 0 I = infinite = possible fire

(this is an ideal case, but it highlights the problem). You need to limit the current through each LED to be somewhere around 10mA, assuming the LED has 0 resistance.

See here for the correct way to wire up an LED:

http://arduino.cc/en/Tutorial/Blink?from=Tutorial.BlinkingLED

Although they are not visible in the image, for each LED I have added a 100 ohm and a 88ohm resistor. is that not enough Resistance?

That is not enough but it will not cause a fire either.

We NEED a schematic of what you were trying to make. Then we need clear photographs of your setup to see that you have implemented what you wanted to make.

In this case the code is irrelevant, no code can cause a fire on its own you need faulty wiring to do that.

It looks like you have a big solder splash under that board. That could be shorting things out.