Hi,
I've been trying to build a hi resolution encoder for a while now with mouse parts, up gearing and so on, but i just came across an easy source of high density encoder wheel and detector - a deskjet printer.
I opened up a HP deskjet printer - 712, and it had a 3" encoder wheel and detector on the shaft connected to the paper rollers.
I got this printer second hand for $5.
plenty of second hand ones around on ebay, gumtree.
you'll need a T10 and T9 torque screwdriver to open it up.
the detector had Q9863 printed on it which is a HP part number, and after a bit of searching found the pinout.
1. gnd
2. channel A
3. +5v
4. Channel B
I hooked it up to an oscilloscope and found it generates TTL level sine waves.
since i needed pulses for my microcontroller, i just connected the channels to a quad schmitt trigger CD4093, then inverted it with the next nand gate on the same chip (tie two inputs to form a NOT gate), and lo and behold, square pulses.
works beautifully. now i am not sure if this detector signals vary in amplitude for slow rotation, but from tests, even very slight movements generated square pulses. so amplitude was sufficient for the schmitt trigger to output pulses.
I don't know the details of the detector but you can see it emit a faint red glow. so its not IR.
and you get true quadrature output with each channel 90 deg apart.
the codewheel has 200LPI printed on it, but i havent counted the number of lines as yet. will do so shortly.
but even if it is say 1500 lines per 360 deg rev, using quadrature, that would be 6000 ppr. and if you gear even as low as 1:2, you'd get 12000 ppr.
whats even better is there is one more detector on the print carriage head thats linear. i'm not sure if it would work well as rotary, but worth a try.
Now to print my own codewheels, i bought this transparency film from officeworks for $19,
http://www.officeworks.com.au/retail...ies/ACPP100C20 and used this software to print my own wheel on my work photocopier/printer machine.
http://www.mindspring.com/~tom2000/Delphi/Codewheel.html#Generating%20a%20Cod ewheel
I was able to print a 1400 line codewheel with a diameter of 4 inches at 600 dpi.
So if you don't have access to an old deskjet, you can use the OHP paper above to print your own wheel and get much higher densities than a wheel from a ball mouse.
thought it might be useful for those who haven't built one yet.