Making LED voltmeter

4 bit ADC?

that's not very acurate (1/16). You need at least a 10 bit ADC and a quiet and acurate voltage reference.

Microchip ( has several application notes on their website for the 10 bit incorporated ADC and multiplexing LED's. To get started programming PIC's is a little daunting, but once you get it, they become incorporated into more and more designs. <p>If you are just starting out in microprocessors, a chip with a built in BASIC compiler <b>AND</b> a 10bit ADC <b>AND</b> a routine for shifting data out serially to a LED controller (like the Maxim MAX7219) is the BX-24 from Netmedia ( There is also a chipset from which uses Sprint Basic -- and you can get Sprintbasic as freeware if the program doesn't go over a certain number of lines.

The Harris/Intersil chips were nice in their time, but I don't think they are particularly user friendly for DIY'rs. I fixed a piece of instrumentation a while back -- I traced the problem to one of their chips -- again common anode display --