I am trying to use Nema 17 stepper motors. I have tried two A4988 and one DRV8825 driver for them. The problem is when I try to the Vref reading the numbers on on the multi meter jump all around. It goes high then low and back and forth. When I try to adjust the pot on the drivers it doesn't change anything, the reading keeps fluctuating and quite rapidly.
I am grounding on the driver module or the power supply and touching the pot with the positive lead. I have tried two different multi meters and it does the same thing with both. I set to meters to DC volts. I checked both meters by checking the power supply voltage. They both read that fine. I have tried a couple of different power supplies.
I have tested the Vref with the driver and motor set up correctly and just the driver with power to it.
I heard there is a way to check the current getting to the motor but haven't tried that, don't know how.
I have had the Nema 17 set up with the Nano and the drivers and can get the motor to run but I don't want to damage the motor with too much current.
I think I have something set up wrong but can't figure out what it is.
A Nema 17 stepper motor is a stepper motor with a 1.7 x 1.7 inch (42 x 42mm) faceplate. The NEMA 17 merely designates the motor's faceplate, it defines nothing about the motor. The actual specifications for your motor would help.
Next the actuql stepper motor power is pulses so what were you expecting to see on a meter? I would expect the motor voltage and current to be bouncing around. A scope is likely the best way to see what is going to the motor. You need to understand the waveshapes used to drive a stepper motor and how rotational speed and direction are accomplished.
The two motors I have tried are rated at, 3.5v @ 1amp, 12v @ 1.5 amps.
I have watched quite a few videos on the internet on how to take a Vref reading and the numbers don't bounce around, they change only if they adjust the pot.
From what I have seen in some of the videos you don't even need the motor hooked up to take the reading.
Try that. Keep in mind that for the A4988, the proper Vref setting depends on the current sense resistor. Since different manufacturers use different sense resistor values, you need to know that value.
Check all your solder joints for good connections with no short circuits between them. You cannot use a breadboard for motor currents, as the tracks will burn.
Please post a hand-drawn wiring diagram, with pins and connections clearly labeled, and links to the motors and power supply.
Well, I've made some progress. I set the two A4988 and one DRV8825 because I am determined to figure out how take a Vref reading and set the pot. I got good readings on all of them this time, the first A4988 at.85, the second at .55 and the DRV8825 at 1.56. The power supply was a wall wort at 4.5v and 1.2a.
I think when I was trying to taking my readings before I didn't have it grounded right, or at all. Today I grounded at the power supply and I got steady numbers.
The only thing is I can't adjust the output with the pot, it stays the same no matter how much or which way I turn it. I think maybe I ruined the pots before by trying too much.