Astable Multivibrator Clicking

[newjackruby]

Heyall,

Here's something interesting...

So, I'm building this fuzz pedal for a friend. I decided to put it in a previously drilled enclosure from a failed project. Said enclosure, however, has two extra holes in it. What to do?

Last night, I decided that those holes would have alternately blinking LEDs in them for no other reason than filling the holes and being weird and original. I found the following circuit online, which works exactly how I wanted it to:





Got it all hooked up, and have a problem. The relay of the blinking LEDs is making a click in the audio signal. Sounds like a distant turn signal when not playing. Anyone have any suggestions on how to make this go away? I feel like I should be able to filter it out with a capacitor somehow. The circuit is only merging with the rest of the pedal at +9v and ground. Figured I'd post here and hope that someone who actually knows something about electrical engineering would have a solution.

Happy weekend!

[PRR]

[newjackruby]

Thanks for the reply. Gave this a shot. Still getting the same clicking.

[antonis]

The relay of the blinking LEDs is making a click in the audio signal.

May I ask the reason for using a relay..??

[newjackruby]

The relay of the blinking LEDs is making a click in the audio signal.

May I ask the reason for using a relay..??

Purely cosmetic. I'm not sure that relay was the right term for me to use. I was just looking for a circuit that would make two LEDs alternate blinking on and off. This circuit works great for that, but it also makes a clicking sound in the audio circuit.

[antonis]

The relay of the blinking LEDs is making a click in the audio signal.

May I ask the reason for using a relay..??

Purely cosmetic.

My bad, then..
(thought you're refering on a "real" (mechanical/solid state) relay..)

Weird for persistent clicking after Paul's mod..
Did blinking rate alter..??

[composition4]

Hi, try this, with the two capacitors being large (100uF - 470uF) electrolytics -

[composition4]

Any luck?

[GibsonGM]

Where is the astable GROUNDED to? That might explain some of why the big cap isn't working - maybe.

[anotherjim]

I notice...
The LED resistors at 470 ohm are small - creating a largish current pulse. Using modern LED's and 9v, I think those resistors should be north of 1k.
We might be assuming the LED's are on a PCB, but if on wires then twist the pair of wires to each LED -  it will reduce pulses being radiated to the audio circuity.

When a transistor switches on, it grounds the positive end of the timing cap, which means the negative end becomes some voltage negative of ground which has to dissipate sometime somewhere. You could put reverse diodes on each transistor base to ground which will clamp out that negative voltage.

You can reduce the timing capacitor current by making the resistors R2 and R3 larger and the caps C1 and C2 correspondingly smaller. If the transistors have decent gain, it might work with R2 and R3 at 470k and the caps of 1uF.

[newjackruby]

Wow, thanks for the replies. My pedal building and internet browsing time have both taken a dive thanks to world events. I will give these ideas a try and report back eventually.