DRV8825 + REPRAPGURU NEMA 17 42STH40-1204 Low voltage? Low current?

Projects General Guidance
1

I have been reading through all the forums and seems like my issue isn't code related but a power issue, and I wanted to get guidance without blowing my driver or motor.
The problem is that I am getting a humming / stuttering noise from the motor, no movement. Sometimes 1 small step on power on if the shaft is moved prior to power on, then the humming. The shaft does hold torque though once powered on.

I have a KS42STH40-1204 Stepper Motor using DRV8825.
External 10V 600ma Power Supply @VMOT and GND
LEONARDO powering DRV8825 at 5v and GND
Vref is measuring @0.70v (equates to 1.4A according to Pololu documentation)
10.6v PSU to VMOT measures 160mA at run time
Coil A measures 0.50V at run time
Coil B measures 0.30V at run time
(Coil A and Coil B pairs checked for continuity)

Wiring diagram attached:

MY CODE

int pinStep = 9;
int pinDirection = 8;


void setup()
{
  pinMode(pinDirection, OUTPUT);
  pinMode(pinStep, OUTPUT);
}

void loop()
{
  digitalWrite(pinDirection, HIGH);
  for (int i = 0; i < 200; i++)
  {
    digitalWrite(pinStep, HIGH);
    delayMicroseconds(500);
    digitalWrite(pinStep, LOW);
    delayMicroseconds(500);
  }
  delay(500);
}

MY CODE Option 2 - Standard Blink program using LED pin only - LOL, code is not a problem as the same humming is happening when no signal is sent to any PINs related to DRV8825

int pinLED = 13;

void setup()
{
  pinMode(pinLED, OUTPUT);
}

void loop()
{
    digitalWrite(pinLED, HIGH);
    delay(500);
    digitalWrite(pinLED, LOW);
    delay(500);
}

EXTRA DETAILS

42STH40-1204 Stepper Motor

Details are limited:
Current: 1.8A Holding Torque:0.36 N.M (50oz*in) Inductance: 2.6 mH

Seen all the DRV8825 youtube video's (most famously):

Used various starter code from:

http://forum.arduino.cc/index.php?topic=324756.0
http://forum.arduino.cc/index.php?topic=277692.0
https://forum.pololu.com/t/a4983-and-a4988-getting-started-guide/2789
etc... etc...

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2

Measuring the coil voltage with a multimeter is not going to help much.

It is very important never to disconnect a wire between the motor and the driver while the driver is powered - it can instantly destroy the driver. Are you sure your driver is OK ?

If you have been trying the motor with code that causes a step every millisec then that is very probably much too fast. Try it with (say) 4 steps per second to start with.

How many amps can your power supply provide? Measuring the current going to the DRV8825 is not meaningful. Do you have the 100µF capacitor across the power supply?

You have linked to my Simple Stepper Code - it should work.

...R
Stepper Motor Basics

3

Robin2:
How many amps can your power supply provide? Measuring the current going to the DRV8825 is not meaningful. Do you have the 100µF capacitor across the power supply?

Thanks for the reply Robin:

Yes, 100uf 63v capacitor just as in the modified diagram shown above.

PSU is a 10v 600mA wall wart, but the DRV8825 only seems to draw 160mA.

As I mentioned, even if I load the standard BLink program, and no PINS are connected to the DRV8825, the humming/grinding/stuttering noise exists.

I don't think the driver is dead, I have only measured voltage at the pin leads while powered on (never disconnected accidentally). To test regardless, I used a new DRV8825 and after VRef adjustment to 0.68V, I came to the same results.

I am thinking do I need to upgrade my PSU to a higher amperage? Regardless of what VRef is outputting? Some how 160mA draw at VMot is not making sense....

4

rcatank:
PSU is a 10v 600mA wall wart, but the DRV8825 only seems to draw 160mA.

If think about it 160mA must be meaningless because your motor needs to draw up to 1.8 amps (or whatever your current limit is set at).

I am thinking do I need to upgrade my PSU to a higher amperage? Regardless of what VRef is outputting? Some how 160mA draw at VMot is not making sense....

The amount of amps that your power supply can produce has no effect on the voltage that is set by VRef.

10v x 0.6 amps = 6 watts which may be marginal, but I don't think you have told us the coil resistance of your motor so I don't know how many watts the motor needs. If it was my project I would use at least a 12v 1 amp power supply, and 18v or 24v would be better.

You can measure the coil current by putting an ammeter into the coil circuit while the system is de-powered. Just be careful that nothing can disconnect by accident while the power is on.

...R

5

Measure the resistance of the two coils. If there is a significant difference then one of them may be faulty.

When you said "KS42STH40-1204" did you mean "KS42STH40-1204A". I didn't find many references to "-1204" but plenty for "-1204A"