Atmega ticking

Other Hardware General Electronics
4

Wow thanks for the quick and thorough reply!
Probably should have prefaced this before, but I'm just a dumb mechanical engineer... the whole electrical/electronics thing is Greek to me sometimes, but i'm learning :slight_smile:

Away from my personal computer right now, but can post full schematic and layout later.

To answer your main question, yes, the ticking is audible if I put my ear next to the atmega. And I'm 99% sure its not coming from the relays. It's a bit quieter than the relays normally sound when switching.

  1. There is no voltage supply to any portion of the audio path. Its all passive. The relays basically just route the audio signal and the uC is there to switch them.

  2. The audio sections and digital sections do share a ground. I've heard/read about separating digital/non-digital grounds. But to be honest, I have no idea how to actually do this (maybe this discussion should wait until i post the schem).

  3. Again, dumb ME here so bear with me. The intent of the 100r and 10uF [R1 & C1] are to create a LPF to smooth the 9VDC to the regulator, RIGHT?? Also, this noise doesn't sound like a typical ground loop hum which I am VERY familiar with unfortunately.

  4. Nope. No diodes across the coils. I've used this exact same setup with an ATtiny85 and single relay for bypassing a single pedal with no issues. This design is really just an extension (x5) of something that I've continually used with no problem. These are TQ2-L-5V single coil latching relays. Maybe I'm not thinking about this right, but wouldn't the diode prevent the uC from reversing the HIGH/LOW signals to the coil pins to reset the switches??

  5. I have no idea what you're talking about :stuck_out_tongue:

So the power schem I posted is from another project that needed 5V, 3.3V, 9V, and 4.5V... none of the other supplies are in this project, just the 5V. But as a side note, on the previous project, the separate power rails were all screwed up until I added those 100r resistors.

Guitar pedals are a hobby of mine and D1 and C1 are components i see in lots of schematics. Yes D1 is for reverse polarity protection, and i believe C1 is a smoothing cap for DC ripples??