Stepper motors & controllers

[az]

For a uni project I'm looking for a stepper and controller that can be controlled and run on power from USB (if that is not possible, I'll settle for RS232 or PCMCIA) - anyone know of such a thing?

Thank you very much

AZ

[gt40]

Most I've seen work off the printer port - does this work for you?

[az]

It has to work off a standard notebook computer, actually I don't know what interfaces they have nowadays (I suspect only USB and PC-Card).

Also, it would be VERY nice if it could also get its power from the notebook (I don't need a lot of torque or high speed).

AZ

[Marshmallowman]

hehe..one of those lego kits

[degrub]

An inductive load like a motor would likely burn out a USB port. You would have to know the startup current at that voltage. How about using an external supply with the control signals from the USB ?

Frank

[spadnos]

Originally posted by az
It has to work off a standard notebook computer, actually I don't know what interfaces they have nowadays (I suspect only USB and PC-Card).

Also, it would be VERY nice if it could also get its power from the notebook (I don't need a lot of torque or high speed).

AZ

You won't want to power any motor from any PC port. It's almost too much to power a stepper controller from a parallel port (in fact, it is too much). USB can only supply around 100mA at 5V, so that's out (laptops are also notorious for having sub-standard output voltages/currents).

It would help to know what kinds of things you will want to do with the motor(s), and how many you want to run simultaneously (and if you need to control multiple axes relative to each other (like drawing circles).

In general, a simple stepper setup has 3 pieces: the controller (generates step pulses at the desired rate), the driver (actually powers the phases of the motor), and the motor

For low speed stuff, you can use the PC to generate step pulses. Low speed in this case is anything under around 1000-5000 pulses per second. Even those slow rates need low level drivers to work well. Once you get to somewhat higher pulse rates, you need a standalone board or a realtime OS on the PC, which Windows certainly isn't, and Linux mostly isn't.

There are several options for standalone boards:
Something like this can work if you only want the computer to say "Go clockwise" or "Go counterclockwise" (or "Stop").
If you need more flexibility, you can go for a CNC type controller like DeskCNC. This is driven by a Windows program. I'm not sure how controllable the unit is from software other than their CAM controller, but it is a good board. It costs $125.
You can use a manual pulse generator, like the one I recently designed. I haven't written the software for serial control yet, but I did put a serial port on the board. It was designed to output step and direction signals to a separate driver, but it can also directly drive a 4 phase unipolar stepper motor (the kind you'd buy from DigiKey in the US), at up to 30 or so volts, 1 amp (the transistors are rated for 1 amp, though these will melt the solder on the board before they burn up). I can add simple software to accept a speed and direction from the computer. This is $200 (though I can probably sell it for a bit less, since you wouldn't need the $20 encoder knob used for manual control)

Next in line is the motor driver. There are a bunch that are fairly cheap (in the $30-100 range per motor)
Here's one on eBay that could work OK if all you want is for the computer to command FWD or REV motion, at a single (preset on the board) speed. You'll need to be sure that you have a omputer with a parallel port, or a custom serial card, to be able to tell this card what to do. It is cheap, though.
Here's another one on eBay - a little more expensive, and more of a pain to power, plus it needs a pulse train generated by the computer.
For larger motors, you should look into something like the GeckoDrives. These are VERY well made drivers, which take step and direction signals. G201 - $114 each.

I have lots more info on this (in case you couldn't tell) - I've been researching things necessary for a CNC retrofit of a milling machine, and motors/drivers/controllers are a big part of that.

Let me know if you need any more info.

- Steve

[Wulfman]

might be worthwhile to check c't. they had a project like this running some time ago. I think they built some kind of usb-controlled camera (security style) or so, but I'm not sure.

mfg
wulfman

[William]

I don't know of any particular part that you can buy; but it has to be possible; because canon have a line of scanners entirelyy powered from a USB port, and that has a stepper motor in it. Maybe dissasemble one & have a look?

[az]

Thanks Frank (I feared this would be the case), Steve, Wolf.

OK, here's the lowdown:

We need to turn a Sensor in defined steps (say, 5°). We don't need a lot of torque or speed, but I need to be able to control the motor one step at a time, left and right. This should be controlled by a standard notebook, so no PCI controller cards, no parallel port. Ideally USB. It would be nice if it could be powered from the laptop, but if that isn't going to work, we'll just use a separate power supply.

I am not entirely clear about the software side of things. What kind of software does a controller usually ship with? How can I automate stuff? Is it easy to code for this? (As you may be able to tell, this is my first uni project and I've never seen a stepper/driver/controller before.)

AZ

[Fluff]

Can you not look at a canon usb powered scanner and get the stuff out of that. That has a stepper motor inside.

[Drizzt]

Originally posted by az

OK, here's the lowdown:
[cut]
AZ

I cannot help you on the power source side (even if I'm pretty sure you can find a stepper that can be powered by RS232 or USB or else), however on the programming side:



If you go for USB, you will need a really cood programmer as USB is not that easy to use.

If you don't need excessive speed, the best thing you can do is go for Visual Basic and COM ports. COM ports are common, and VB is really easy to use regard them.

If you really need speed and millimetric control, simply use C.

It would be really nice to have the stepper and the sensor powered by their own source, and control them via an Irda COM port
(that is, it's really easy to do)

[az]

I was hoping that controllers came with libraries containing the functions to easily use them. Damn

AZ

[TransformX]

Most old notebook computers (2-3 year old ones, P-III 500) have a parallel port...

[az]

Yeah, but I'd want this to work with ideally any Windows notebook, though I'd settle for RS232.

AZ

[Fluff]

https://www.rswww.com

have a look on there