Assuming my new M41A counter with sound works properly when the prototype boards arrive from China (they have been made and dispatched, I'm just waiting for them to arrive then I can start building and testing) I guess my next job will be to design and build an M51 smart gun equivalent.
I've already started on the design part (in the hope that the M41A design is correct) though there are few things I need to tweak before I send them off to be prototyped. I've decided to drop the card edge connector that I use for programming the M41A version, even though it makes my life harder when building, but it does make the overall size as small as possible.
Here's my initial design:
As you can see there is even more electronics involved in this model, but fortunately the larger size gives me more room to play: