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Topic: Pololu A4988 wiring and current limiting (Read 479 times) previous topic - next topic

blabby

Hello,
I've been following this tutorial on wiring and setting up the Pololu A4988 with a small bipolar stepper motor .
I have followed the directions closely, however when I get to the point where I mesure the reference voltage using the potentiometer on the board I get 0.
I have provided the correct wiring and a picture of mine. In my picture I have removed the motor wires for clarity.






Did I miss something in my wiring ? Or is my A4988 not working ?

Please ask if any additional information is needed
Thanks for your help

MarkT

[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

rpt007

Before you ask:
Did you really read and understand How to use this forum ?
AND:
Do you have already some solution or is a part of the problem sitting in front of the screen?  :)

rpt007

Picture looks ok. I suspect that reset# and sleep# are connected?
Before you ask:
Did you really read and understand How to use this forum ?
AND:
Do you have already some solution or is a part of the problem sitting in front of the screen?  :)

blabby

As rpt007 stated enable is low by default

and it's hard to see in the picture but there yes reset# and sleep# are connected

Robin2

This Simple Stepper Code can be used for testing. It does not need any library.

...R
Stepper Motor Basics

Two or three hours spent thinking and reading documentation solves most programming problems.

rpt007

#6
Jun 23, 2016, 09:13 pm Last Edit: Jun 23, 2016, 09:18 pm by rpt007
one more thought:

did you make sure you connected the right wires (means coil A and coil B) to the driver?
You can measure, what wires belong together. Sometimes you cannot rely on the datasheet's colors, as I had to experience from time to time.

So I always measure before I connect the wires to exclude that kind of failure.

@Robin2:
Just for my personal interest: Do you know if you can adjust VRef of a driver with no stepper connected?
I didn't check the schematics so far and I always adjust the current with a stepper connected (or by listening to the stepper sound) watching my laboratory power supply.
Before you ask:
Did you really read and understand How to use this forum ?
AND:
Do you have already some solution or is a part of the problem sitting in front of the screen?  :)

Robin2

Do you know if you can adjust VRef of a driver with no stepper connected?
I don't think I ever tried that. So the answer is "I don't know"

...R
Two or three hours spent thinking and reading documentation solves most programming problems.

blabby

#8
Jun 24, 2016, 11:34 am Last Edit: Jun 24, 2016, 12:34 pm by blabby
Yes I have measured and identified the wires of my stepper motor (they were different from the datasheet!).

I just bought a new A4988 just in case, but I still have the same issue.

I dont see what I am doing wrong


Just to be clear, there is 5V between the red and the blue, but I am getting 0 volts here :

MarkT

BTW those cheap breadboard hookup wires cannot carry large currents, they are designed for
signals.  The breadboard itself will be struggling with the current too, watch out for overheating
and oxidized connections.

Use solid core wire directly for power and motar, it can carry more current.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

Robin2

The picture in Reply #8 suggests that you are measuring the voltage between GND and the screw-driver part of the potentiometer. What is that intended to show?

...R
Two or three hours spent thinking and reading documentation solves most programming problems.

TomGeorge

#11
Jun 24, 2016, 01:03 pm Last Edit: Jun 24, 2016, 01:07 pm by TomGeorge
Hi.
You protoboard has a break in the power line along the side, you need to bridge the gaps.


Tom... :)
Everything runs on smoke, let the smoke out, it stops running....

blabby

#12
Jun 24, 2016, 02:05 pm Last Edit: Jun 24, 2016, 02:12 pm by blabby
Thanks for the tip MarkT, I'll keep that in mind for later

According to this guide I am following and others I found online, the voltage between GND and the screw-driver part of the potentiometer is intended to show my reference voltage.

Thanks for the response but ss stated above I have 5V between the red and blue wires, and between the two pins on the board. The break in my power line after the board.

blabby

#13
Jun 24, 2016, 02:27 pm Last Edit: Jun 24, 2016, 02:36 pm by blabby
@Robin2 and @rpt007
According to this youtube video from pololu, you do not need the motor to be connected to mesure or adjust the VRef of a driver

bvoi

Any resolution on this, blabby?  I am experiencing the same problem where I am unable to adjust the vref because it always reads 0 on the multimeter.

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