sorry I am trying to get the image up. i will try again in a bit. thank you!
This is my set up to try to make a potentiometer of sorts out of a graphite stick:
I am wiping the green clip across the graphite and get really good variation in speed of blinking of the led. The problem is that the graphite gets really hot. I have tried a variety of resistors between power and the red clip but this just reduces my range and the responsiveness of the led. Does anyone have any suggestions on how I ought to go about doing this. My ultimate goal is to use a graphite drawing in place of the stick of graphite. Thanks in advance.
First off put a resistor in line with that LED, otherwise you will damage your arduino.
Second you need to put a resistor in line with the graphite rod, this will reduce the range but there is not much you can do about that with a simple setup.
Learn about ohms law.
It would help if you could measure and report the resistance of your graphite bar.
What I would do is ground one end of the bar as you have now. Connect the other end not to B+ but to a 500-ohm resistor. Also connect this to the AREF. Then the other end of the 500 ohm resistor goes to B+.
Then set the analogue input to use the external reference. The range of voltages on the input will be small, but it should work.
Thanks to both of you. I will try this. But to Grumpy Mike: doesn´t pin 13 on the Arduino have a built in resistor. I will add one to my set up but shouldn´t be ok with out one. Aslo, I have looked at Ohm´s law but only know how to use it when I am checking the values of a resistance that would exist given a particular current and voltage- not to predict what resistance I would need to add given a particular current and voltage. Sorry for the super basic questions, I´m a new tinkerer.