Hi, I want to use a three-legged (voltage divider) rotational potentiometer as an analog input for my Arduino NG rev. C board. Unfortunately, I only have a 470 ohm potentiometer. I'm not sure if I can use this potentiometer with Arduino: it's quite a low resistance (compared to kiloohm potis) - a quick calculation gives 5V/470ohm = ~ 11 mA current flow through the poti.
Is this too much electric current for the Arduino board?
What is the maximum electric current I can take from the 5V onboard source without damaging it?
Can I say: "The higher the resistance of the potentiometer, the better?", as this minimizes electric current flow -> minizmizes energy consumptions?
Thank you for your help.
The board should easily supply another 11mA. The power supply makes about 500mA and the base Arduino consumes something under 100mA.
About "higher is better", there is a rub... higher resistance will lower the power consumption which is nice, but it also increases the effect of the current consumed by the analog input pin. In a situation where you are turning a knob by hand that effect won't matter. The second effect is that at very high resistances (>>10Mohm? just guessing, it's been a while since I needed that neuron) you will start to see "shot noise" where the discrete nature of electrons raises its ugly head.
just to chime in, the 470 ohm will work, but it's a waste of juice. YEs the Arduino will produce the current for the pot, but according to the Atmega datasheet the analog pin only needs miniscule amounts of current... in the range of micramperes (milliamps X .001!)
A 10K is usually a good choice.
Thank you very much for your helpful replies. I will try to write my first potentiometer program today :). Bye, Abdull