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Author Topic: 24 Volt, 4 Amp Nema 23 Stepper Motors  (Read 7084 times)
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I'm in a bit of a fix. We're setting up an installation with 10 motors in a weeks time. I was using small motors with very little power because they were super cheap but I needed more juice. I came across this ebay site with really cheap Stepper Motors (http://myworld.ebay.co.uk/cnc4you/?_trksid=p4340.l2559). The guy was super helpful and really nice but he doesn't know much about Arduinos. I would recommend him to anyone making CNC equipment! I didn't want a 4-axis pre-built driver though...

Being a little impulsive, I bought them and figured I would sort the controller out later. I bought a 24V 15A power supply to run all of them and an Adafruit Motor Controller Shield
http://www.adafruit.com/index.php?main_page=product_info&cPath=17_21&products_id=81.
I knew I was going to blow up the transistor so I wired only 2 of the 4 coils in the motor (it is an 8 wire motor).

Ran for about 3 seconds and puff! no more L293D.


Any help would be most appreciated.
J
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If time is an issue you are best off with a motor driver module, like the one you identified from Solarbotics (the L298 one) or our own Rugged Motor Driver. Really, if that will work depends upon the voltage you are applying and the current you want to pump into each phase. It sounds like 24V is the voltage given the power supply you bought but I'm not sure you mentioned what the per-phase coil current is for the motors you bought, nor what current you WANT to run them at to get the required torque.

Any more details on your motors or application?

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The Gadget Shield: accelerometer, RGB LED, IR transmit/receive, speaker, microphone, light sensor, potentiometer, pushbuttons
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That was the idea behind the Adafruit but in getting the motor to just spin, I blew out the transistor. I've attached the two data sheets I have for it.

I initially had it rigged to a 24V 0.8A power supply from Maplin running through a Darlington array and it grunted a little bit but never spun. Thus the increased amps.

It's still not entirely clear to me how I control the amperage going into the motor which is also why I'm depending on the motor driver. How do I know the Rugged Motor Driver won't blow out? It's only rated to 2.8A whilst the motor is 1.3-4.

The application: It is running a vertical assembly up and down with bits of timber (as light as possible) and some bending sheet material. The weight is as yet unknown which is why I'd like the protection of a bigger motor.

* Nema motor dimensions.pdf (24.41 KB - downloaded 95 times.)
* Nema motor info.pdf (316.47 KB - downloaded 60 times.)
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The motor info link is a duff, nothing is shown in the displayable document.

You need to know what current you want to drive. Four amps per coil is a lot of power, you will have to have a driver that has separate FETs for this.

There are two ways of limiting the current. One is by applying the appropriate voltage to the coils, the other is by using a chopping driver. These have current sensing resistors and turn off the voltage when the current rises to the value set. Therefore you get the chopping effect on the voltage. This has the advantage of being able to get the maximum speed out of a motor.

It sounds like you are applying too much voltage either for the motor or your driver.
« Last Edit: March 20, 2011, 07:01:04 pm by Grumpy_Mike » Logged

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There's no such thing as a 24V 4A Nema 23 stepper motor - it would require forced liquid cooling.  If its 4A its probably about 2V or so - high current motors like this should be driven with a current-limiting driver.  The supply can be 24V in this case as the driver does buck conversion - high voltage means the motors can be driven faster (this extra voltage overcomes the back-EMF and does useful work).

I suspect the original spec meant there was a 24V driver circuit available for it.

Basically there are two approaches to stepper motor design - one uses high resistance windings to limit the current so that they can be voltage driven and not burn out.  These motors can't spin very fast.  The other uses low-resistance low-inductance windings to maximize operating frequency and these are designed for constant-current drive and are capable of high-performance.
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The motor is actually 24-50V, 1.3-4A. It has very low resistance in the motor--the distributor told me that. I was looking into a current limiter but got lost in the pre-made driver boards
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Ah yes, the voltage is just a recommendation for driver circuitry.  I note there are some fairly cheap and well featured 3- and 4-axis stepper controllers on ebay - should be something that can handle that kind of current (you don't necessarily need to run a motor at its full current, BTW, so a controller where you can tune the current is a good idea).  They tend to have a parallel port connector but the control is usually a 5V logic step and a direction signal per axis.  Microstepping is good if you can afford it - motors run much smoother and more quietly.
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