Multiple Stepper Drivers but one step pin

Projects General Guidance
1

Hi,

I have wired up 2 stepper drivers (DRV8825) such that the STEP pin on both drivers is connected to the same Arduino Uno pin, and the EN pins are connected to two separate Arduino Uno pins.

e.g. EN1 connected to Arduino UNO pin 2, EN2 connected to Arduino UNO pin 3 and STP (both drivers) connected to Arduino UNO pin 4.

When I activate one stepper motor (NEMA17) via EN1 pin, the stepper fails to turn but does make a sound. However, when I disconnect the STP pin on the second driver of the motor I am not turning, then motor 1 turns without any issues.

I would like to know why this is the case, and is there a way around it so I can continue to use one Arduino UNO Pin to control STP of multiple drivers? (All of the motors will be running at the same speed, and only one motor will be turning at any one time).

I hope this makes sense.

Asim

2

asimbhuta:
When I activate one stepper motor (NEMA17) via EN1 pin, the stepper fails to turn but does make a sound. However, when I disconnect the STP pin on the second driver of the motor I am not turning, then motor 1 turns without any issues.

If the exact same thing happens regardless of which motor is disabled then it seems as if an Arduino I/O pin cannot provide enough current to trigger the two drivers. I have never tried this but I find it rather surprising. If that is the reason then there is a risk that your Arduino's I/O pin will be overloaded and damaged.

Is there any reason why you can't use two separate step pins on your Arduino?

...R

3

Yes, the same thing happens regardless of which motor I enable.

I'll be driving at least 3 motors, and have 3 IR through-beam sensors and will be attaching a barcode scanner as well. So the less I/O pins I use the better.

As an iteration, I was hoping that I could get 2 motors working with this setup.

I do find it surprising as well, as I would've thought that the driver that is disabled wouldn't pull any current.

Worst case scenario, I'll just use a MEGA, but would be a good learning experience to figure out how to solve this problem.

Thanks

4

Just out of curiosity will the single step pin drive both motors at the same time when the two DRV8825s are enabled?

Posting your program would be a big help or a short program that illustrates the problem. Also make a pencil diagram that clearly shows all your connections and post a photo of the drawing. See this Simple Image Guide

...R

5

Both drivers will never be enabled at the same time. My power supply wouldn't be able to handle it anyway.

I'll post the code and pencil drawing shortly.

6

asimbhuta:
Both drivers will never be enabled at the same time.

I understand that. I am just curious to know if your problem has anything to do with the fact that one of the drivers is disabled.

Can't you get a suitable power supply to use temporarily for a test?

...R