Current sensing on stepper

[originator]

I have used this AD628 IC on a product to detect current on a single motor application, and it works very well, with highly sensitive detection. In the case of 4 motors however, I am wondering about the PS design. The single motor design uses the sense resistor on the input to the motor driver. For 4 motors, it is not that simple. So I am considreing using four 4 amp transformers, 4 bridge rectifiers and caps, 4 variable regulators, and a sense resistor on each driver boards power in to detect current on each motor. Is this the best method to you guys to accomplish 4 motor detection?

http://www.analog.com/UploadedFiles/...eets/AD628.pdf

[ViperTX]

Well that would most likely work....and you're trying to monitor the current of all the steppers for a reason?

Are you going to monitor the current in both motor directions.....clockwise and counter clockwise rotation?

[smarbaga]

perhaps something like the attached
plan will help

[originator]

Not for CNC use, for multiple doors, so that if an obstruction is detected, the door will retract. The only direction that the processor will monitor is the closing direction of the door. Another application is skylights, where one motor pushes the skylight up, another pushes it over. Another is a 4 axis machine in the works with no encoders.

[originator]

Thanks Smarbaga. So you prefer one large >10 amp supply over 4 smaller ones? I will look into a transformer that larger plus regulator, I've never built anything that larger yet. Sounds simpler though. I can buy 3.5 amp transformers off the shelf locally. Any preferences on a reguator?

[ViperTX]

Well for door closure....you will have changes in current usage based on increasing friction as the door is repeatidly used...in that case I would defer to an infared obstruction sensor.

In any other application I would opt for a current shunt (current sense resistor) in line with the motor lead(s)...

[smarbaga]

well actually i would prefer separate power supplies, that way if one goes you are not totally out of commision, the cost is higher tho.