Arduino Forum

Using Arduino => Motors, Mechanics, Power and CNC => Topic started by: Ronbabious on Dec 01, 2018, 08:21 am

Title: [HELP] Powering a stepper motor with a battery
Post by: Ronbabious on Dec 01, 2018, 08:21 am
Hello there!
I'm doing an arduino project where I use a stepper motor SM42HT38-1684AC (https://www.google.dk/search?rlz=1C1GGRV_enDK751DK751&ei=LfgAXJiCCoLzsAGak62QDA&q=SM42HT38-1684AC+datasheet&oq=SM42HT38-1684AC+datasheet&gs_l=psy-ab.3..33i10.41296.42601..42665...0.0..0.70.561.9......0....1..gws-wiz.mxD0mbU6z1M) it's connected to a L298N (http://www.alldatasheet.com/datasheet-pdf/pdf/22440/STMICROELECTRONICS/L298N.html) driver. I'm trying to power it with a battery, according to the stepper motors datasheet it should need 3V and 1.6A. I used 3x3.7v 1400mAh (https://m.aliexpress.com/item/32854931810.html?pid=808_0000_0101&spm=a2g0n.search-amp.list.32854931810&aff_trace_key=&aff_platform=msite&m_page_id=6531amp-gmCoZXumfGzKR7Trs685JQ1543617470010) connected in parallel, but literally nothing happens when I power the stepper. When the stepper is connected to a wall adapter it runs just as it is supposed to. Anyone have an idea of what could be wrong?
Title: Re: [HELP] Powering a stepper motor with a battery
Post by: Robin2 on Dec 01, 2018, 09:27 am
A low impedance stepper motor like that is not suitable for driving with an L298. You need a specialized stepper driver like a Pololu DRV8825.

Also the motor is not intended to be driven at 3v. 12v or 24v would be more appropriate. The specialized stepper drivers can be adjusted to limit the current to protect the motor.

And, stepper motors are very inefficient so are most unsuited to power from batteries. They draw full current even when stationary.

What is the project you want to create? Maybe there is a better option.

...R
Stepper Motor Basics (http://forum.arduino.cc/index.php?topic=284828.0)
Simple Stepper Code (http://forum.arduino.cc/index.php?topic=277692.0)
Title: Re: [HELP] Powering a stepper motor with a battery
Post by: Ronbabious on Dec 01, 2018, 10:33 am
Thanks for replying Robin
The project is a ping pong ball shooter and is for a course I'm taking. I'm using the stepper to pull back a hammer of sorts that locks in place at a certain position and is then released to 'kick' the pong ball. At my first attempt, I tried using a step-up converter to step the batteries up to 12v, since the wall adapter I was using had an output of 12v and 1A and worked fine. But after having no luck, I looked up the datasheet and read that I took 3v, figured I'd try to remove the step up, but that didn't work either.

I am aware the batteries aren't suited for stepper motors, but since this project only needs to work with batteries for a short demo, I thought it would be fine.

Hope this clarification can assist.
Title: Re: [HELP] Powering a stepper motor with a battery
Post by: jremington on Dec 01, 2018, 04:39 pm
Quote
I thought it would be fine.
Obviously, it is not.

Use the wall adapter for the demo, and you are all done.
Title: Re: [HELP] Powering a stepper motor with a battery
Post by: Robin2 on Dec 01, 2018, 07:01 pm
I'm using the stepper to pull back a hammer of sorts that locks in place at a certain position and is then released to 'kick' the pong ball.
I suspect a geared DC motor would be more suited to that. Maybe something like the Pololu micro-gear motors which are widely available at much lower prices. There is also a widely available gearmotor in a plastic housing which has a bigger DC motor.

...R
Title: Re: [HELP] Powering a stepper motor with a battery
Post by: MorganS on Dec 02, 2018, 09:44 am
You realize that the L298N drops a lot of volts? Powering it at 3V leaves basically zero for the output. Everything is lost in the inefficiency of that driver.

You need a proper stepper driver like the DRV8825 and you need to power it with a voltage much higher than the stepper's nominal voltage. 12V is good for most purposes but higher is better.
Title: Re: [HELP] Powering a stepper motor with a battery
Post by: MarkT on Dec 02, 2018, 02:36 pm
Usually the notion of "battery" and "stepper motor" in the same sentence is a warning.

Steppers are _considerably_ more power hungry than alternatives, and consume power
constantly (not just when under load).  If you don't need easy position holding or
open-loop position control, a stepper is the wrong answer.