Quote Originally Posted by Mad Professor View Post
Well with not quite knowing what is going on with regards to the current sensing resistors I tought it would be best to test how much current the board is pulling.

I am using a bench PSU with a clean adjustable voltage output, the PSU shows me the set voltage and current load.

I have preset the PSU to 13.8volts.

The board by it's self with no stepper motors connected is pulling 0.20a.

Here are the reading with just one stepper motor connected, with the board set to enable and motors at idle.

DIP Switches 3-6 are set to ON.

Bipolar Parallel
DIP Switches 1-2
ON/ON: 1.23a - 0.20a = 1.03a total /2 = 0.51a per phase.
OFF/ON: 0.76a - 0.20a = 0.56a total /2 = 0.28a per phase.
ON/OFF: 0.46a - 0.20a = 0.26a total /2 = 0.13a per phase.
OFF/OFF: 0.25a - 0.20a = 0.05a total /2 = 0.02a per phase.

Bipolar Series
DIP Switches 1-2
ON/ON: 2.10a - 0.20a = 1.90a total /2 = 0.95a per phase.
OFF/ON: 2.10a - 0.20a = 1.90a total /2 = 0.95a per phase.
ON/OFF: 1.05a - 0.20a = 0.85a total /2 = 0.42a per phase.
OFF/OFF: 0.40a - 0.20a = 0.20a total /2 = 0.10a per phase.

All the readings are aprox.

Now I am even more confused then when I started. :confused:
Measure the voltage across each phase... I suspect only one phase is energised when the motor is idling so your "/2" is wrong... what motors are these and what DC resistance?

At a guess I'd say your parallel and series figures are swapped. Again whats the DC resistance across A+ & A- in each mode?

Also remember that the chopper current limiting will regulate peak currents. A 1.5A nominal peak will show up as a 1.5/sqrt(2) RMS current on an analogue meter, i.e. about 1A. It doesnt make a lot of sense unless the resistance of the motors is such that the figure should have been higher on the 100% setting but would need more volts (anything higher than 5ohms would not get to the expected 3A peak - 2.2A rms - current limit on 13.8v, would need 24v)