Pickup winder construction: platen design

[David King]

Jason,
The sensors I used were the reflective type. Once you get the light up and running it's just a matter of measuring the resistance between the two leads of the phototransistor as you pass the sensor over various materials. I used tinfoil tape and black sandpaper to get the greatest change in resistance. Then it's just a matter of fine tuning the distance between the sensor and the disc. It's likely that 1-2 mm is ideal but mine is much further away at about 1cm.
My part number was QRB1113 or QRB1114 I can't remember which but I imagine they will both work. I think one goes high and one goes low when the light gets through to it.
A 3V light source will be simpler to hook up since you can simply buy a 3V DC regulated wallwart power supply/charger or use 2 AA cells.

You might also search for an "opto switch" which might work more like a switch than the typical sensor.

[Jason Rodgers]

Looks like Mouser has plenty of options for reflective and interrupter type switches. If/when I go this way, I'll have to come back for some help with figuring out components and connections.