# Stepper motor and Driver.

Discussion in 'The Projects Forum' started by ganeshram93, Jan 19, 2014.

1. ### ganeshram93 Thread Starter New Member

Jan 19, 2014
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I have 2 different stepper motors for my solar tracker project. The model make isn't specified. Is there any way to find out their voltage and ampere ratings?

And I'd like to know which stepper motor driver and heat sink device is the best suited for them.

And I'd like to know the circuit for connecting the driver and heat sink device.

2. ### MrChips Moderator

Oct 2, 2009
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It might be best for you to post a photograph that also shows a reference to the motor's physical size.

Jan 19, 2014
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4. ### THE_RB AAC Fanatic!

Feb 11, 2008
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Not a great photo. It helps if we can see the label writing on the motor and a ruler next to them for size comparison.

It looks like you have a size 23 and size 17 stepper there, but we can't even see their height which is needed to determine stack number and wattage.

Also we need to know the number of wires of each motor.

Jan 19, 2014
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6. ### THE_RB AAC Fanatic!

Feb 11, 2008
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With 5 wires both are forced to be "unipolar" so it is very important you get unipolar stepper motor drivers.

Motor 1 is a size 23 single stack, with older motors they are typically about 4 watts per phase.

Motor 2 is a size 17 or size 14, probably size 14 as that is 39mm square. That will run about 1.7W per phase.

Now you know the watts per phase, you measure the ohms of each phase coil. So put an ohmeter on 200 ohm range between the common wire and one of the other 4 wires. Common wire is usually white or black (other 4 wires are colours).

Let's say motor 1 reads 52 ohms per coil.
Use this calc;
Isquared = P / R
Isq = 4W / 52 ohms
Isq = 0.0769 (now press the sq root button on calculator)
I = 0.277 = 277mA.

So the motor has correct coil current of 277mA.

Old unipolar motors of that type often were meant for halfstep driving so if you use a microstepping driver you can increase the coil current by about 40%;
277mA * 1.40 = 388mA

ganeshram93 likes this.
7. ### ganeshram93 Thread Starter New Member

Jan 19, 2014
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Thanks a ton.
Can you suggest what Driver, Power transistor and other necessary devices can be used for the tracker circuit?
We are having Driver overheating problems and motor doesn't run at times.

8. ### THE_RB AAC Fanatic!

Feb 11, 2008
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The driver choice will depend on the motor current, so please do the ohmmeter test and calaculations as shown in my post above.

If you are worried about the calculation just tell us the ohms and we can help with the calc.

If you google for "unipolar stepper motor driver" there are a lot of options you can buy cheap.

Ebay has some very cheap full step motor drivers, or you can spend a bit more for microstepping.

Or if you want help with the driver you are using now that is overheating, please provide photos and a schematic etc so we can advise with that.

Jan 19, 2014
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10. ### THE_RB AAC Fanatic!

Feb 11, 2008
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That is a very low performance old-fashioned type stepper motor driver.

I suggest again; have a google for "small cheap Unipolar stepper driver module".

11. ### shortbus AAC Fanatic!

Sep 30, 2009
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RB, wouldn't your LinStepper be a good candidate for this?

12. ### THE_RB AAC Fanatic!

Feb 11, 2008
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Sure, it's one candidate. But the Linistepper kit requires time and skill to build and is more expensive than some of the really cheap pre-built drivers.

The OP's name and location (and re-use of old motors) gave me the impression that he might not want to spend much.

THe main benefits of the Linistepper are the ability to turn really smoothly, and programmability to make it do things. Neither is really of that much use here.

I'm not sure if the OP has googled yet, but I just googled for; "ebay" "stepper driver" and the top link showed up this;

http://www.ebay.com.au/itm/Hot-PCB-...tor-Driver-Board-Blue-1-PCS-NEW-/161183229206

For \$1.69 with FREE shipping.

Or this;

http://www.ebay.com.au/itm/New-Dura...LN2003-5V-4-phase-5-line-Hot-SH-/171223796230

Which is a motor AND driver for \$2.70 with free shipping.

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13. ### ganeshram93 Thread Starter New Member

Jan 19, 2014
6
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Yeah will do that