That explanation makes sense in some ways, but I've got a nagging doubt. Here's why.
On p. 211 of saint's book theres a pic showing a Happ Optical PCB and a mouse PCB, with the caption "a close-up look at a couple of different
optical encoders..." Fast forward to the Ultimarc DIY Optical Sensor page
http://www.ultimarc.com/optipac4.html, where Andy explains the two methods of connecting a spinner to the Opti-Pac, one of which is the Happ Optical PCB. So, back to saint's caption that indicates the two are both optical encoders, and you can see why I assumed that I can connect the mouse PCB to the Opti-Pac.
And another thing...Ultimarc's second option is to glue two opto-switches together, add a resistor, and connect this directly to the Opti-Pac. Seems pretty simple. What I don't understand though is how this simple opto-switch can interface with the Opti-Pac in the same manner as the Happ Optical PCB which has all kinds of resistors, an IC chip, etc. Surely the output of the Happ Optical PCB is of a more refined flavor than the output of the opto-switch pair, and yet the Opti-Pac apparently can understand both very different signals and respond accordingly.
Finally, despite all the above theorizing, the simplest method is no doubt the best, which would be to connect my homemade optical board (the emitter/receiver on the radio shack board, not the mouse PCB) directly to the Opti-Pac. This isn't really any different than the Ultimarc DIY opto-switch option. I've assumed that an additional resistor wouldn't be needed since, according to saint also on p. 211, it's likely that the IR receiver I desoldered from the mouse is actually a pair of receivers in one physical package. If that's the case, then the question becomes which wires from the emitter/receiver board go to what connectors on the Opti-Pac?
Please forgive the lack of brevity....what else am I missing here? Thanks....