On Mon, 06 Jul 2009 18:29:03 -0400, axolotl wrote:
Buerste wrote:
Imagine a simple fractional hp DC gearmotor with a torque limiter or
torque limiting clutch that powers a small machine at 60 or so RPM.
Lets say the machine jams and the torque limiting device kicks out.
How can I cheaply, easily sense this condition and turn off the motor?

This is a personal project and when I get it running it will amaze and
astound!

This is a maybe, since I don't have details of the application. Use a
PTC thermistor (fuse type) limiter for the motor. Let the PTC perform
the torque limiting. Put the LED (properly current limited) of an
optocoupler across the thermistor. When the thermistor goes high
resistance, there will be enough voltage across the optocoupler input to
turn it on. The output of the optocoupler goes back to your office, or
wherever.

Seems like there's just one complicated solution after another
so far in this thread, that all involve adding a bunch of parts.
Here's one that uses *fewer* parts: Take out the torque limiting
device; couple the motor straight through to the machine; take
out the motor mounting bolts; fasten the motor in place with a bit
of string or duct tape. When the machine jams, the motor spins
and its power leads wind up and twist off, stopping the motor.

--
jiw