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any ideas on where to get or how to make a torque based switch? Answered

Im wanting to make a motorised target changing rig that will need to stop against a back stop a set distance away from the shooter. i want to make the rig self contained (i.e. no additional switches etc. down range) so that different distances can be used. the only way i can think to do this is to use a switch that stops the motor when a certain torque is reached. 
any other ideas on how to do this are very welcome 


A simple motor at the shooting end and pulley at the target furthest point will work.

the switch is at the motor end.

target vr 2.jpg

Are we talking indoors or outdoors? You should be able to set up micro switches at the different ranges you want the target to stop at. Now the system can be simple as hitting the down range button and the target goes till it hits the first switch. Hit it again and it goes to the next switch and so on. The same thing happens with the return trip. Or you can set the system up with a micro controller so when button 1 is hit it stops at the first switch, when button 2 is hit it stops at the second switch, ect. The you can have a single button to bring the target all the way back to the shooter.

Alternately you can use a stepper motor to drive the target.Since each step the motor moves equates to a certain distance a micro controller can move the the correct number of steps needed to go the distance you want. Look at DIY CNC and 3D printers to get ideas for how to set that up.

hi, thanks for the reply, I should have said that it will be an indoor range. i have looked at setting up micro switches but i wanted to make the changer self contained without anything else down range. target changers i have used in clubs are just one unit with a couple of guide wires and a loop to move the target holder. the only thing i cant work out is how it stops automatically at the backstop regardless of what range it is at.

as far as stepper or servo motors are concerned, if i can help it id rather not have a micro controller involved just because of added cost and complexity.
sorry to throw these back at you

Treat it like a car window winder - they don't have switches, they just monitor the current - when its high, they stop the motor.

I am guessing that is a safety feature as well so the window doesn't amputate fingers caught in it when its closing.

Absolutely, but have you actually tried stalling a window by hand ?