DIY Dual State Relay issue

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Bumfluff101

New member
Taking inspiration from a number of forumites I'm working on a footswitch project using an ATtiny85 to control two non-latching relays (FTR-B4CA4.5Z), and I've hit a wall that I can't seem to figure out. The logic involves a short press toggling one relay (Engage/Bypass) and a long press cycling/selecting the other (Drive 1/2).

The Problem: I ordered some pcbs and populated everything but the relays do not click when they are supposed to in the circuit. Using a bit of Gemini I've tried to run diagnostics, but things seem to be working - thought I'm now doubting if the circuit is actually right o_O I'm hoping a fresh pair of eyes might spot something I've missed.

Setup:
  • MCU: ATtiny85 running at 1MHz internal clock.
  • Relays: 2 x FTR-B4CA4.5Z (4.5V non-latching).
  • Driver: 2N3904 NPN transistors with 4.7kΩ base resistors and 1N4148 flyback diodes.
  • Power: 9V supply regulated down to a stable 5V.

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leadfoot said:
So, you've now entered the world of embedded systems. :)

Are you sure it isn't the code you're running in the ATtiny85?
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Lol yep

I think the code works, as standard there is 5v on each of the coil pins, on pressing the switch, pin 1 on the really drops to about 169mv which should effectively ground it and switch the relay state but it..er .. doesn't
 
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