[GreenKeys] Lorenz dual motor speed control

[jdangus at att.net]

It's been an interesting project.

The whole things started as a result of discussing the i-Telex project with
Henning. I wanted to be able to run 66 WPM for the i-Telex system and
be able to switch speeds to 60 WPM for playing with Amateur radio RTTY.
AND...I wanted to accomplish this without ANY adjustments. Admittedly,
there is one adjustment, but it's for adjusting the bias on the photo diode.
It has no effect on the speed calibration.

The first picture is the photo-diode and optical pick up pair that looks at
the spots on the edge of the motor. At the required RPM of either 2454
for 60 WPM operation or 2700 for 66 WPM the sensor output is either
495 Hz or 450 Hz respectively.

The second picture is the control card sitting under the pair of resistors
that are in series with the motor and are switched in and out by the
controller. The solid state relay is a zero crossing (SCR) type to minimize
and switching transients and any subsequent RF interference.

Final results are 2455 RPM (+1 RPM) for 60 WPM operation and 2699
RPM (-1 RPM) for 66 WPM operation. An accuracy of better than .05%.

And a special thanks to both Henning and Heinz for their assistance
with this project.

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