I am building a power supply using an LM317. I have decided to use a potentiometer to control the voltage. I want to include a 4 digit display to display the output voltage. Any idea on how I can measure the voltage coming out of the LM317? Keep in mind it will be more that 5 volts, so the analogRead function in an Arduino won't do the job.
If you were willing to settle for only 3 digits, and the LM317 will be producing less than 99v, this unit from yourduino might be useful. However, I suspect you want more accuracy, and want to do it from electronics. But if you wanted to save time: http://arduino-direct.com/sunshop/index.php?l=product_detail&p=247
(they also have green and blue lcds at a slightly higher price).
While I am at the beginning of learning about electronics, I'm not sure why you can't use a voltage divider, since it can reduce the voltage to within 5v that the Arduino can read (and then in the Arduino you multiply to get the actual voltage). I can imagine you would need a ladder or some such if you need to deal with a wide range of voltages.