 # Quick Question

Hi,

I just got an Arduino Mega, and I’ve been messing around with several components.

I want to try testing a rheostat into the analog input to get a reading over the range of 0 to 1023. The rheostat I have is only 25 ohms. I want to hook it up as in this example: http://arduino.cc/en/Tutorial/AnalogInput, but I’m afraid that 25ohms is too little and excessive current will burn something on the Arduino. Should I be worried about the current going into the analog input? How much is too much?

Thanks

The formula for determining current flow is V = IR. With a fixed value of V = 5 (volts), and a resistance (R) of 25 Ohms, the current flow (I) will be 200 mA. That is too much for the Arduino to supply.

The maximum out of any one pin is 40mA. The maximum in to any one oin is 50mA. The total out for all pins is 200mA.

The trim pots (pot = potentiometer = variable resistor) that come with the experimenter kits are usually 10 KOhm and that’s a good value for the Arduino. 10 KOhm is only a 0.5 mA current draw at 5 V, and that shows that a lot can be done with a little current.