IS501 sensor -- my solution
ard at p850ug1.demon.co.uk
Mon Oct 4 15:42:30 CDT 2010
> Hi Tony
> Your solution to the waveform is interesting. You added the capacitor
> to fix the problem caused by the 74LS14. The problem is that the
> hysteresis of the LS14 is so large that it eats up the phase
> margines of the roughly sine/cosine from the optical sensors.
I don't think this is the same problem. Without the capacitors, and with
the 470R resistors, I was getting waveforms with roughtly 1:1 mark-space
ratio, and while not exactly in quadrature, pretty darn close. The only
problem was that every so often (perhaps 1 in every 10000 pulses), there
would be a glitch in one of the waveforms. It's not supply relateded, and
I couldn't repodcude it by, say, jiggling the encoder disk.
But that glitch was taken by the elctronics as a valid pulse which upset
AAdding the capacitors hasn't noticeably changed the mark:space ratio or
the phasing. But it's got rid of the glitches.
A lot of optical mice use the '14 and the output signals look pretty good
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