On 2010-07-25, Ignoramus8473 wrote:

[ ... ]

I actually have a tachometer thingy, if I can find a way
attach it the spindle, I could know the speed more precisely. It
counts rotations.

Hmm ... some mechanical tachometers which I have include a
rubber-tired wheel which has a circumference of either 1/2 foot or 1
foot (thus diameters of 0.3.8197" or 1.9099") to reed in FPM or FPM*2.

If you have a surface on the spindle which is cylindrical and
accessible, you can measure the diameter, and calculate the expected FPM
for a given RPM -- then tune for that.

Or -- find a way to mount a magnet biased pickup coil near the
bull gear teeth and count the pulses as the teeth pass by. Of course,
you need to know the number of teeth, but then you can make something
which will convert this into a quite accurate RPM. (Higher speeds don't
need as many sensor points to give speed fairly quickly, but for very
slow speeds, the large number of teeth will give faster readings.

Enjoy,
DoN.

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