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Topic: Stepper Motors -> powering them up (Read 368 times) previous topic - next topic

Shaare

Greetings,


My son just finished is first robotic arm prototype with servos and a joystick using an arduino.
See the video here. :)

https://youtu.be/-acm28uq5tw


After buying really really cheap stepper motors that are too weak, I got my son a couple of better stepper motors that are to be controlled via the same arduino. I'm told they should be independently powered. I have also sourced a bench power supply to test these stepper motors. Now, we need to learn how to power them.

Later on, how do you get power to these steppers from a wall outlet?

Most likely someone here faced this kind of issue before and because it involves electricity I thought it more prudent to ask people first. Anyone can spend some time providing some guidance, something to read on maybe, that would be greatly appreciated.

Thank you kindly for you time,

Antoine & Alex in Vancouver, BC :)

Note:

My son (11) and I have watched quite a number of youtube videos to find the answer, including reading lots of posts. I even bought a couple of Udemy course he's started on. Please understand, though this likely will look like an easy question, its not an easy question for beginners like us. I'm learning as well in order to help him out and spend time with him. And since it involves electricity and the potential to destroy electronics which are costly (for me at least) I hope that this forum is civilized and that those that don't have anything good to say won't.

Robin2

#1
Jul 13, 2019, 10:30 pm Last Edit: Jul 13, 2019, 10:30 pm by Robin2
First of all you will need a stepper motor driver for each of your stepper motors. The A4988 or DRV8825 drivers will be suitable for those motors - see the Pololu website which also has lots of useful info about using them. They are widely available, not just from Pololu but it may be worthwhile getting genuine Pololu modules to start with as their advice obviously is designed for their modules.

A bench power supply may not be the best choice because its power regulation may fight with the current regulation within the stepper drivers. I suggest you set the power supply to a high voltage (subject to the max for the driver, of course) and to a high current and allow the stepper drivers to protect the motors. The Pololu website explains how to adjust the driver current limit.

Any mains power supply that provides enough current at a suitable voltage can be used. I use a 19v laptop power supply to drive similar motors with A4988 drivers.

...R
Stepper Motor Basics
Simple Stepper Code
Two or three hours spent thinking and reading documentation solves most programming problems.

Shaare

Hi Robin and thank you for your reply. My son and I will get reading those links now. Also thank you for the laptop brick idea, indeed, that should work maybe some resistances needed? I'll get reading now with Alex.

Wish you a great evening!

Antoine & Alex

Robin2

maybe some resistances needed?
If you mean that you should add some resistors between the power supply and the stepper drivers then NO, definitely not.


Tell us why you think "resistance" might be needed.

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

MarkT

A bench power supply may not be the best choice because its power regulation may fight with the current regulation within the stepper drivers. I suggest you set the power supply to a high voltage (subject to the max for the driver, of course) and to a high current and allow the stepper drivers to protect the motors.
My advice is limit the current to 1A, voltage 12V in first instance, then if the current limit is completely wrong on the DRV8825's they won't overheat instantly - though if you've set the current correctly it shouldn't be an issue.

Current limiting can interfere with the chip, but its better than frying the chip through over-current(!)

Follow the procedure from Polulo for setting the current with no motor connected.

Never connect/disconnect a motor from a powered up stepper driver. 
Either connect motor windings to the output of a stepper driver, or connect nothing - the chip requires a highly inductive load to function.
The connections must be solid (breadboarding isn't ideal for this reason).  Any dodgy connections here and you can blow up the driver just as if you hot-swapped the motor...

Have a couple of DRV8825 modules spare, they are cheap enough to warrant it.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

Robin2

My advice is limit the current to 1A, voltage 12V in first instance,
I don't have a bench power supply myself but I have the impression from other Threads that if the bench power supply applies its limit before the stepper motor reaches its limit the whole system gets confused - I envisage a race condition, but I may be completely wrong or it may depend on the specifics of the bench power supply.

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

Shaare

If you mean that you should add some resistors between the power supply and the stepper drivers then NO, definitely not.


Tell us why you think "resistance" might be needed.

...R
Hi Robin,

The power supply I have for him

(https://www.amazon.ca/gp/product/B07H4LFN6F/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1)

is rated to 10 amps and so I think I'm supposed to read this, I hope, as 'it'll provide up to 10 amps' right? I just just started a udemy course on electronics with my son.

https://www.udemy.com/electronics-for-complete-beginners

Thank you for your input!

Antoine and Alex

Robin2

That power supply should work fine. However a higher voltage would be better if you want the motors to move fast.

Make sure to adjust the current limit on the stepper drivers to 0.4 amps to protect the motors.

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

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