Ball mouse turned into cheap tachometer...

Well, first off, what's wrong with the circuit that comes with the
mouse?  You can always desolder the sensors from the board but connect
them to it with wires.  If you want to build your own electronics,
IIRC, the guts are something like this: pulsed led on one side, dual
phototransistor with either common emitters or common collectors.  The
led is pulsed to save power since a serial port can't supply much.  You
won't need to do that.  You'll want to put a resistor, probably 10k or
so but you can experiment, in series with each phototransistor across
your 5v supply.  Put the center taps of those into a 74LS14 or a
comparator with hysteresis to clean up the signals.  Unless you're
spinning it way faster than a mouse does you can probably decode the
quadrature signals in software on an mcu.

chris

lmcgill2@uiuc.edu wrote:

   I would just use the circuits and all that are in the mouse.  Google
for the PS2 protocol for serial mice and write a "SPI-ish" micro
interface to talk to the mouse.  In this way you get the fully X/Y
movement which should do wonders for dead reconning on your robot.

DLC
--
-------------------------------------------------
Dennis Clark          TTT Enterprises
www.techtoystoday.com
-------------------------------------------------