Power supply is 4 D cells producing 6.29V on my meter, measured at the Vmot and Gnd pins. A 100 µf electrolytic capacitor is as close as possible on my breadboard. I tried to duplicate the minimal wiring as well as possible, as show in your spec sheet, and in the current setting video.
With the pot turned fully CCW vref is 6.14V. Turned fully CW it is 5.08V. Stepper motor is not connected (5V NEMA 14).
Without changing the breadboard, I unplugged the DRV8834 and replaced it with an A4988 and got similar results ( voltages were withing 0.05 of the DRV8834). I must be doing something wrong, but haven’t been able to figure out what. I can send a photo of the breadboard if that would help.
Can you post some pictures that show your setup and how you are measuring VREF?
Too late. Since I posted
my issue, I’ve taken the breadboard apart and tried several
different layouts. I gave up on the DRV8834 and the A4988 and
ordered a L298N. Thanks for the offer of help. I do appreciate
I figure that if you are kind enough to offer help, I should do a better job of accepting it. After all, I can’t do much until the L298N arrives. I redid the breadboard only this time I used a different power source for logic and the DRV8834. I thought perhaps the 6V overpowered the driver, which has a max of 5.5V. The reading were about the same taking into consideration the logic voltage was now 5 instead of 6. With 5.05V in, adjusting the pot gave a range of 5.05 to 4.03V. I snapped a photo but I’m not sure how to attach it. Hope this works.
So, I realized I was using the wrong pin to measure the reference voltage. It works now. I still appreciate your help. You made me think a little harder. Thanks.
I am glad to hear you decided to give it another shot and got it working!
I am not sure how you have things powered now, but your logic and Arduino power connections in your picture look problematic. I would definitely avoid applying logic power greater than 5.5V to the DRV8834 or your Arduino since that could potentially damage them; they should really be powered with a regulated 5V supply. Also, if you are going to power the Arduino through its 5V pin, you will need to be especially cautious to not accidentally connect power backwards to it, and it is generally not good practice to do that while the Arduino is connected to USB or external power (such as through the barrel jack). That would essentially short different power supplies together, which is especially bad if the voltages are different.
Thanks Patrick. While
testing my sketch, I have powered the Arduino via the USB only, so
the DRV8834 is being powered by the Arduino. In other words, there
has been no change to the breadboard other than removal of the 5V
logic connection. So, do you recommend powering the Arduino via
the barrel jack once things are done?
I assumed from your earlier picture that you were separately providing >6 V to your boards (where you have the label “6.29V”), but I realize now that could be from when you measured it using the wrong reference. Powering your Arduino from USB or the barrel jack and then powering the DRV8834 logic from your Arduino’s 5V pin sounds like a good approach.