Hello,
My project will contain sections of 3-4 blue leds that each draw20ma and are powered by a external wallwart, i'm going to use the arduino to ground the circuit to allow the leds to light.
I've read that the arduino will only allow 50ma draw, is this when the arduino is powering the leds itself?
sorry if this is a noobs question, just don't want to burn my arduino (you know what its like with for first born).
Neill :-/
The processor's datasheet has all the details but basically...
Try to stay at or below 20 mA per pin and you should be fine.
is the datasheet info for Ma when that drawing power from the arduino or grounding an external powersupply?
i'm not sure if i'm explaining it right. the arduino is not supplying power to the leds but completing the led circuit by grounding the leds (powered by a wallwart 9v)
Neill
the datasheet info for Ma when that drawing power from the arduino or grounding an external powersupply?
it covers both
Try to stay at or below 20 mA per pin and you should be fine.
As CB says, 4 pins each controlling 20mA is no problem.
But although a safety margin below maximum ratings is prudent in a production design, I would not worry about driving up to 40ma per pin as long as the 200mA total was not exceeded.
I suggest drawing up and posting a picture (schematic) of what you want to do.
the arduino is not supplying power to the leds but completing the led circuit by grounding the leds (powered by a wallwart 9v)
9 volts applied directly to an Arduino pin will damage it.
the arduino is not supplying power to the leds but completing the led circuit by grounding the leds
The power is flowing through the arduino to ground, that is the same as as far as the arduino is concerned as if the power were flowing from the positive supply to the output pin.
The total of all power flowing has to be less than 200mA.
If you have a 9V supply you have to have a transistor to do the switching.