I'm using a 555 timer circuit similar to this one to blink a couple of LEDs at around 1 to 30 Hz:
The oscillations are causing huge spikes on the 5V supply line. There is an audio circuit running off the same 5V and the op-amps are picking up those spikes, rendering them audible.
I've tried a few things to decouple the 555 circuit:
- insert a 220 Ω resistor between 5V and the supply pin on the 555 to limit the current draw
- add 0.1 µF and 47 µF caps between the supply pin on the 555 and GND
- add a 220 µF cap between 5V and GND
All of those seem to mitigate the spikes somewhat, but they're still clearly audible. What else could I do? Is the 555 just so greedy on current that I'd be better off with a different kind of timer?