Hi,
I had a project with only two pins left that I wanted to add some indicators LEDs to, I came up with a quick and dirty solution that might work for others.
The two quantities I wanted to represent were the level of steering and throttle intervention being applied by an Arduino to the control signals of a radio controlled car. As these quantities are 'levels' I naturally thought of implementing a simple level/vu meter and driving it from a single pin using analogWrite.
Using a simple low pass filter between the Arduino analog output pin and vu meter I get a perfectly good representation of my intervention levels using a single pin to drive a four LED indicator.
Obviously if I had another pin free I could have used the more conventional approach of a shift register but its nice to do something a little different now and then.
Using the LM324 to make vu meters is well covered on the web, as are dedicated vu meter ICs such as LM3916. They are not just limited to audio use and really can add an extra degree of cool to a project.
Duane B
