555 timer as a VCO

by Stephen Hobley on March 23, 2009

Taking a break from robots and lasers to work on my MIDI to DRSSTC Tesla coil adapter. (?)

How cool is the 555 timer? I just discovered that by modulating the control pin (5) with a varying voltage you can alter the output frequency.

Effectively a VCO – wow.
(Do I sound like a geek yet?)

Although my attempts to use this with the Atmel168 have not been too successful as it only provides PWM analog out, and even with smoothing via an RC net it’s still too shaky to produce musical notes.

So I’ve got two choices, either use a DAC to send out the control voltage, although the range is a bit limited. Or use a digipot to either act as a potentiometer and supply control voltage, or replace R2 in the astable configuration of the 555.

I think I’ll try the latter…


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