Stepper Motor Power Issues

Hi Guys, I am new to the Arduino community and purchased an Uno about a month ago. I am doing a project that involves the use of an old printer stepper motor.

Using this found from Arduino site (http://www.tigoe.net/pcomp/code/circuits/motors/stepper-motors/) I wired everything up using a L293D dual H-bridge and a bi-polar stepper from the printer. Everything was working perfect. I first used the 5 volt pin off the board for the motor supply, which I don't think was the correct thing to do, but it seemed to work just fine (only slow and not very powerful which I expected).

The stepper motor is rated for 24 volts so after I got all the code squared away I decided to use the old power supply from the printer. Sure enough it had a 24 volt DC rail so I put the + side of the rail directly into the H-Bridge chip (pin 8) and the - side to the common ground. This is when everything went south. When I turned it on the motor was just twitching, I burned up an H-Bridge chip, and now my Uno wont connect to the computer (but still powers up an all).

The specs on the H-Bridge says it can handle 36 volts. What did I do wrong?

(I am also by no means a electronic expert so I am sorry for improper terms/ silly comments)

Specs: Stepper Motor: M42SP-4N L293D dual H-bridge data sheet: http://www.futurlec.com/Others/L293.shtml Power supply: From printer, had 2 24volts rails (assuming 1 rail for each stepper), and a 5 volts rail.

Need pictures and schematics of how you had things hooked up. Other than that, the best we could say is that 'something' fried...

First you have to be careful with bipolar stepper motors, the voltage rating can be meaningless.

The parameters you must find are the current rating and the winding resistance (which you can measure).

Bipolar motors are usually driven with a constant-current chopper driver, and the voltage across the winding depends more on the motor rotation speed (back-EMF) than the IR-drop across the windings.

The M42SP-4 series motors come in several varieties, including unipolar with high-resistance windings and bipolar with 5 ohm windings. If your motor is 5ohm and you put a static 24V across it then 5A would try to flow and melt the L293D - molten chips connected to 24V will then likely put 24V on every pin (including your Arduino).

The 293 is not a chopper driver and wouldn't be appropriate for a high-performance bipolar motor - or for driving this motor at high speed. There are chopper driver chips like the A4988 and L6208 and various others that are good to drive bipolar motors from high voltage supplies.

The windings read 5 ohms so I sent to many amps thru the chip which is what fried it.

So the next question I have is: Are there 2 types of bi-polar stepper motors, being chopping and normal? Can I just use ohms law to determine the voltage needed by the stepper?

Thanks for your help.

MarkT: First you have to be careful with bipolar stepper motors, the voltage rating can be meaningless.

The parameters you must find are the current rating and the winding resistance (which you can measure).

Bipolar motors are usually driven with a constant-current chopper driver, and the voltage across the winding depends more on the motor rotation speed (back-EMF) than the IR-drop across the windings.

The M42SP-4 series motors come in several varieties, including unipolar with high-resistance windings and bipolar with 5 ohm windings. If your motor is 5ohm and you put a static 24V across it then 5A would try to flow and melt the L293D - molten chips connected to 24V will then likely put 24V on every pin (including your Arduino).

The 293 is not a chopper driver and wouldn't be appropriate for a high-performance bipolar motor - or for driving this motor at high speed. There are chopper driver chips like the A4988 and L6208 and various others that are good to drive bipolar motors from high voltage supplies.

Are there 2 types of bi-polar stepper motors, being chopping and normal?

No just one sort of motor. Two types of driver though.

Just supplying the motor with a voltage to give it the rated current will work but it will not be able to move as fast as if you use a chopping driver and a higher voltage.

Ok, I understand now. Thanks for your help.

I think i'm going to get an EasyDriver stepper motor driver from sparkfun. https://www.sparkfun.com/products/10267

But now the question is how much voltage can I give the chip so I wont burn anything out again? Is this the 24 volts that the stepper motor data sheet called out?

The other question I have that may be off topic for this thread has to do with the code. But, can I still use the same stepper code: Stepper(steps, pin1, pin2, pin3, pin4), stepper.step(), etc. I'm going to assume not b/c I see that there is only the step and direction pin

Are you sure your motor is rated for 24V? that's awfully high for a bipolar stepper. These types of drivers control the current that flows through the motor winding, whatever the voltage (but don't exceed their max voltage). You don't need the stepper library when you use a driver with step and dir inputs, just connect two output pins, set the direction and send pulses on the step pin.

The issue is that bipolar motors with low-resistance windings are designed for chopper-drive, so that the voltage rating often reflects what the winding insulation is rated for and/or the expected back-EMF at the full rated speed of the motor.

If you have a stepper motor with all three ratings, current, resistance and voltage, then its easy to see if the voltage matches the resistance x current rating - if so then its clearly not aimed at chopper-drive.

Many large high performance stepper motors have ratings like current = 5A, resistance = 0.6 ohms, and would run from something like 80V via a chopper-style driver. If you ran them from 3V you'd be lucky to get 60rpm out of them, from the chopper drive 1000-2000rpm are more typical figures. Most of the 80V is needed to overcome back-EMF at these speeds.

I thought he meant that there's 24V written on the stepper, I do have old unipolar 24V steppers but modern bipolar ones use much lower voltages, if not using a chopper.