Read current (voltage drop across resistor) in two directions

[eblc1388]

Hi Odysseas,

I looked again at your motor control schematic and cannot be sure it will work as you would have intended.

Supply of each motor is controlled via a single 1P2T relay but then you switched the common of all the motors via another relay.

This will not allow individual motor to rotate in either direction. You have created a situation that a motor can either run in a certain direction or just stop, depending on the state of its control relay.

In order to run motor in both directions, you would need a 2P2T relay for each motor to reverse the current to the motor.

If you place the current measurement resistor of each motor before this relay then all the current will be in a single direction and you don't have to use differential Opamp for voltage measurement.

Is this really what you have wanted?

edited: correct bad spelling.

 

[Odysseas]

Yes, this is fine. I am aware of the restriction that all motors can only run in one direction or be off, but, as I said, I cannot modify the wiring of the motors, so I have no influence here to change this.

I am presently testing a different solution, without precision current metering... I'll post again here once I know whether or not it works

 

[Speakerguy]

Bidirectional current sense amplifier? Try MAX4081.