Potentiometer to limit dc motor torque

Other Hardware Motors, Mechanics, Power and CNC
1

Hi,

I am using an arduino to control a driveway gate. Amongst other things, it has a 24v 48w dc motor, driven by two relays that determine the direction of the gate. The dc motor has a hall sensor that is used to count revolutions.

I need to add a potentiometer to limit the torque so that the gate can sense an obstruction and have the dc motor stop.

I am new to electronics. How can I achieve this? I have read some posts where a hall sensor can be used to measure current. Is this correct, and if so, can it be used to measure both revolutions and current? If not, what component should I add to allow me to measure the current, and hence be able to limit it with the potentiometer?

Thanks for any help.

Lee

2

The Hall sensor you need to measure current is different from the one you need to measure revolutions. The first measures magnetic field generated by current, the second sense magnetic field cause by a magnet attached to the motor shaft.

Here SparkFun Current Sensor Breakout - ACS723 - SEN-13679 - SparkFun Electronics is a Hall sensor on a breakout board that might be suitable for your current measurement.

3

Hi dc42,

Thanks again for the info and explanation. I presume that one that measures up to 5A will be sufficient for my needs. What do you think? Presumably the motor will use just 2A (24v 48w), but could it spike and damage the ACS712?

Regards,

Lee

4

LeeD:
Thanks again for the info and explanation. I presume that one that measures up to 5A will be sufficient for my needs. What do you think? Presumably the motor will use just 2A (24v 48w), but could it spike and damage the ACS712?

The datasheet for the ACS712 says it can take 100A for 100ms, so I think it should be OK.

5

Excellent. Once again, many thanks.