At 08:02 98.06.22.§Zª GxŸÞZª€šx -0400, Timothy D. Gray wrote:
>I dont think a tach would be so expensive, 1 led, 1 phototransistor, 1
>tiny piece of plastic on the motor shaft. total cost 98 cents and no
>special circutry to translate to PIC compatable signals, just measure the
>frequency.

Cheaper way- measure frequency of collector switching spikes on supply.

>
>
>On Mon, 22 Jun 1998, Ron Fial wrote:
>
>> Another (perhaps old fashiond) way to measure DC permanent magnet motor
speed is to measure the back