Hello all,
It's been a while since I was last here...

I'm in a world of hurt trying to wire up some form of spindle speed detection for a lathe.

I've got some Darlington photointerruptors (KTIR0121DS) which I think are the right thing for the job. I want to power them from a 5V supply, and sense the outputs on inputs to a parallel port (the PCPPS breakout board from DIYCNC).

Can anyone suggest the right circuit and resistor values for this?
I've made 3 versions now, and all of them seemed to work OK (swing from 0.6V to 5V when interrupted) until connected to the parallel port inputs. Once connected though the voltages were different, and only moved around 0.2V when interrupted, which is not enough to change the inputs.

I'm clearly doing something wrong, but after 3 attempts to start from scratch and recalculate, I haven't got things running...

Can anyone help?