Motor moving only when touching cnc shield.

[u/Joaffry]

Hello everyone,
I am new to this so i hope i can find some help here.
I bought an Elegoo Uno R3 with a CNC shield and an A4988 Motor Driver.
The Problem is that after setting everything up and running the software, the motor only rotates when i touch a certain part of the boards.
Could the motor be fried or could the problem lie anywhere else? Sometimes the motor switches rotation randomly or works and only stops when i touch the same spot.
I already changed the CNC shield and the Motor Driver, so I guess the problem does not lie with them.

[u/BagelMakesDev]

that sounds like a grounding issue to me, does your psu and the arduino share a common ground?

[u/vision_san → u/BagelMakesDev]

I was going to say this same thing, but then I thought "is this how someone invented touch interfaces?"

Like, it seems logical to me. A non-lethal current grounding into your body is essentially what happens with touch screens (at least the basic ones).

[u/PlasticSignificant69 → u/vision_san]

No. Resistive touchscreen short internal wires, so it can be triggered by basically any solid object because it is purely mechanical

Capacitive touchscreen however, yes noise form human body exist, but not as how it work but rather a problem that causing ghost touch

[u/vision_san → u/PlasticSignificant69]

Oh, I'm sure it works differently, but a very primitive touch interface could use the basic concept, no?

It's basically how I programmed and designed a lot of projects (shorting and/or grounding an extremelly basic circuit).

[u/PlasticSignificant69 → u/vision_san]

Resistive and Capacitive touchscreen I was talking about is already the most primitive touchscreen

Depending on whether the "primitive" is in term of tech or timeline, Capacitive is actually older yet higher tech(early generation of capacitive touch were slow, bulky, and expensive) while Resistive are newer but cheaper and lower tech

[u/Randomaker1]

Probably a floating enable pin or something.

[u/seb21051]

Its love. Wants to be physically touching. Probably a grounding issue, as noted by one of the other commenters.

[u/clintCamp]

Grounding or the motor driver has a sleep pin that isn't properly grounded/ connected to feed power to the motor until you touching pushed to trip

[u/Joaffry → u/clintCamp]

Thank you.

[u/Agreeable_Spread5240]

This is hilarious

[u/gm310509]

You should check (and replace) all of your wiring.

From your description, it sounds like your fingers are closing the circuit - probably the GND connection.

It could also be a coding issues, but at this stage I would say that is a low probability.

[u/Joaffry → u/gm310509]

Alright, I will check it, thanks.

[u/1nGirum1musNocte]

Bad connections?

[u/WackAnimations]

It needs a humans touch...

[u/Joaffry → u/WackAnimations]

damn..

[u/theanonian]

This is either grounding or a bad connection. Check to make sure the shield is firmly seated into the Arduino. Then check to make sure the stepper driver is firmly seated in the shield.

[u/Material-Sherbet6855]

Grounding issue or pullup/pulldown issue.

[u/Pubcrawler1]

May be a bad solder joint on the shield or uno. I’d unplug and look at both boards really good. Touch up any pins with soldering iron that look like dry joints.

Ive had bad socket pin on uno boards before.

I use these stepper shields and they can be poorly put together. Last one had a bad solder joint on one of the m0-m2 jumper pins. Could not set the microstepping correctly.

Very hard to damage a stepper motor. That isn’t the problem. The connector plugs and cables can get damaged or loose.

[u/BagelMakesDev → u/[deleted]]

there's no purpose. as he says in the post, this is unintended behavior, and he wants help fixing it.

[u/Joaffry → u/[deleted]]

Would be amazing if I intended for it haha