bipolar stepper motor beginner

ambroxio

Hello. I have a handful of bipolar (4 wire) stepper motors around . searching I found some info about theese and I want to be able to use them with the propeller . Before I get the parts I need I would like smoeone to give me the right direction about this .

This is the schematic I will try
http://www.tigoe.net/pcomp/img/bipolar_stepper.png

Can I run the stepper motors with 3.3 volts ¿¿ Is there something missing in the schematic for using with the propeller ¿

ambroxio

there are many chances I dont find the parts I need at the local electronics store so I might try this circuit here http://www.cs.uiowa.edu/~jones/step/circuitsf/14.gif

any recommendations about this one would be nice too

ElectricAye

ambroxio wrote: »

...

Can I run the stepper motors with 3.3 volts ¿¿ Is there something missing in the schematic for using with the propeller ¿

Can you provide a link or data sheet for the type of motors you intend to use? Chances are that 3.3 volts will be too low to get any good performance out of a stepper motor. It's not uncommon to run stepper motors at 24 volts, for example.

ElectricAye

You might have a look at these:

http://forums.parallax.com/showthread.php?120436-How-best-to-control-a-2-amp-stepper-motor-with-the-Propeller

http://dkc1.digikey.com/us/en/tod/STMicroelectronics/StepperFundamentals_NoAudio/Stepper_Fundamentals_NoAudio.swf

LoopyByteloose

Often a beginner wants to just make their motor (either normal DC or stepper) just work with the voltage available. I am a bit suspicious of your request to run at 3.3 volts.

First of all, though the microprocessor requires a regulated voltage to run right; motors can do very well without a regulated supply -- even when an interim stage from the microprocessor controls the direction, speed, and/or step.

Many begineers are completely ignoring the reality that the motor they have requires much more power than the microprocessor can provide. One has to consider how much power the motor requires in order to provide the right voltage and right amperage since Watts = Volts X Amps. And then work backwards to gain proper control. If you are unsure, you can use something that provides much more than the required amps at the appropriate volts - like a TIP120 or TIP125 darlingtion. But you still need to somehow determine the power requirements of the motor by doing the math and at least applying Ohms Law and the Power equation.

More often than not, the begineer has a motor without any specs and will never get the specs. But fortunately, many of the motors available are tolerant of abuses. I'd just try test runs as 6 and 12VDC to see what happens. Internal heat or an incredibly fast spin are warnings that you are abusing the motor. So keep your thumb on the motor when you apply power and if it gets too hot to touch, disconnect.

Using motors at 3.3 or 5 volts DC is possible, but H-bridges and Darlingtons and MOSfets have far less leaway for poor design. If you really want to make a sucessful motor control, it is probably easier to just provide 12VDC for the motor than to fool around with more tempermental low voltage designs.

Transistors and diodes have an internal voltage drop of 0.7v each and when you start using them in control combinations, these voltage drops begin to eat up your much needed Voltage. For instance, a Darlington has Two voltage drops or 1.4v - so with a 3.3volt supply, the best the motor will get is 1.9 volts. Rather wimpy results.

LoopyByteloose

Yes, beginners overlook many of the issues of motor control, but they really want some quick results. I'm just trying to offer a better starting point. 3.3volts driving a mystery stepper is rather challenging. One needs to at least measure the internal resistance of the coils and get some idea of what it might do at 3.3volts. Directly connected to Propeller I/O is likely to cause damage to the Propeller. And of course, you mention that motors can easily perform better with higher volts AND less amps.

ambroxio

ok . thanks for the pacience ^^

Most stepper motors i have dont have any information or useful identifier on them. So if I use a 24 volt power supply I guess its gonna be ok right.

Thanks for the datasheets and the code ldbruce, the first schematic I mention seems simple to me . and the article has code examples
http://www.tigoe.net/pcomp/code/circuits/motors/stepper-motors
What problems could I have with this schematic ¿

I see there would be two voltages, 5 volts for the inputs and enable, and the motor voltage, also there would be 3.3 for the prop; is it just a matter of connecting those 2 grounds ( 5 volts and 24 volts, and get the props 3.3 from the 5 volts ) and the wires "control 1" and "control 2" to propeller pins or do I need optoisolation ( as you mentioned it )

ambroxio

got it . thanks !

Ray0665

Speaking of beginners could my object "Mother of all Led Sequencers" and a little external circuitry be used for experimental purposes?
I had someone ask me this but I didn't have the skills to properly answer when I saw this thread.

Ray0665

As you may know the sequencer generates waveforms as well as led patterns. My poor knowledge of stepper motors leads me to believe that you need several phase related signals to properly energize the coils such that the motor turns. Now it is obvious that the prop outputs cannot drive the motor coils with either the voltage nor the current so thats where the external circuitry comes in. I was thinking in terms of some transistors that would be the drive circuits. Clearly this is just for experimental purposes So the question remains.

Ray0665

Thanks Sorry I didnt intend to hijack this thread.
FYI the original question was about a display that had a bunch of lights and a stepper motor to position something (I dont have a lot of details) So anyway he did not want to invest in a real driver and was more interested in positioning than moving something. I have no Idea if anything came of it, and I've never seen him on the forums.