Problem using common ground for different voltages on negative of power suply

[borjaperez]

Hello everyone. Always I've thinker that I could use a common ground for multiple voltage circuits.
I am using a stepper motor with a driver to manage it.
The stepper works with 12 V and I must supply 5V to driver. I was connecting both grounds to the battery negative (battery of 12V). But I got stuck with it because stepper seems to work in a direction but when it has to turn in the other direction I only listen to a little noise, but no movement observed. In fact it shakes.
In the moment I've connected driver supply ground (5V) to the ground pin in Arduino board, everything has begun to work right.
What does it happen? I need to know something I don't know?

Thanks a lot

[jremington]

Please post a link to the stepper driver, the stepper motor and a photo of a hand drawn wiring diagram, with all pins and connection clearly labeled.

[Ballscrewbob]

There is a sticky thread somewhere about "common ground"
In general it is usually best to tie grounds together at a common point.

Whilst not always the case and there are circumstances where grounds should not be tied together most small voltage items can share a ground.

OK here is the link Common ground and why you need one

[gilshultz]

Think of ground as your reference point. On the Arduino you turn a led on and off, if you measure it from the Arduino ground to the anode it will be high when it is on and low when it is off. Now take another board and put it beside the arduino. Leave your ground connected to the arduino and turn on the second board with a different power supply and measure the voltages, they will not make any sense. Now connect the grounds together, not you have the same reference point and the measurements will be good. Chips work the same they need a reference point when one communicates with another. Hopefully this helps.

[johnerrington]

@borjaperez

I need to know something I don't know

so do we.

Which Arduino are you using?

Can you do a sketch of how the parts are connected?

How to make a schematic you can post.

When you submit a question on the forum you will usually need to add a schematic (circuit diagram). The tutorial that follows will explain some ways to create a useful image; however lets start by explaining how to add the image to your post. Its easy. Having created the image all you need to do is : Save the image somewhere convenient - maybe your desktop Start your post, and place the cursor (insertion point) where you want the image to be shown; [upload image to forum] 3: click th…

[borjaperez]

Hello everyone, sorry for not replying during the week.
I post a picture of the connections. I need to connect both grounds to the expansion board.
However, looking at the bottom side of the board both pins seems to be connected and therefore the same.
If I don't click in the ground to Arduino it does not work and if I don't click in the ground of the battery it does no work. Both must be connected to work.
That is what I don't understand what it is happening

I've drawn arrows on those pins to help you indentify them.

Thanks so much.

Ooh and Arduino board is an Arduino uno

[JohnLincoln]

You should always have a fuse in the battery lead when using lead acid batteries.
They can supply large fault currents.

[tinman13kup]

Wouldn't say you have a problem at all. You need a complete circuit from each power source (positive and negative (ground))
You are using power from the battery (12v to run the motor) and 5v from the uno to control the motor. Both circuits are on the same circuit board, and without anything isolating the circuits from each other the ground will be tied together

[johnerrington]

This explains with diagrams

Common ground and why you need one

Two common methods of grounding. Common ground can be broken out as two types. (simplified) Both are known as GROUND. In most cases you will probably use something similar to the post from Perry However if you are planning a CNC, multiple motors, servos, actuators etc. type of project there is another method to consider. STAR GROUNDING In its most simplistic it is a central point where all grounds meet using a "star" formation. Often also used in audio, musical instrument situations to na…