over current detection

Brian Carpenter

I am not sure i am using the right term for it. I am looking to create a very similar feature as is in my wife's honda pilot window regulator motor.When it senses an obstruction, it stops and goes back down. It is my assumption that what it is doing is sensing a current out side of its bounds and the electronics reverse the motor. Is this a fair assumption?
So, i have a motor that drives a gear and screw. i want it to stop when it meets a certain torque or current.

Any pointers as where to start?

Is this simple with passives or is there an ic that does this for me?
current wont exceed an amp.

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T Chap

For motor current sensing I use an IC called an AD628, which is a programmable gain difference amp. Set the gain to suit your needs, feed the output to a 339 comparator and set a reference level on the other comp input. You can tweak this to get extremely sensitive current readings. I have tried other current sensing ICs but haven't found anything as nice as this IC for this purpose.

Brian Carpenter

i found this. it looks like what i am after.

http://www.romanblack.com/current.htm

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Phil Pilgrim (PhiPi)

Brain,

That should do it. For greater precision, you can substitute a comparator for the transistor circuit.

-Phil

Brian Carpenter

thanks guys. i will put one of these together

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