cheap, USB controlled, simple mechanical device (example: rotating gear)?

March 19, 2008 2:44 AM

I've made a small mechanical device but need help to find a USB-connected, -powered and -controlled part that gives mechanical input. It should be slow, turned on/off from computer, and really cheap.

The sought after part could come in many shapes and sizes, for example, a turning gear or wheel or a pistong. I can adapt the rest to work with almost anything that moves, as long as it satisfies these criteria:

- the movement is slow
- the movement can be turned on/off throught the computer (ideally it should run in both linux and windows)
- it is USB powered (i.e. no standalone power supply)
- it is really cheap (< 15$ , ideally around 5$)

The last criteria is important. Lego Mindstorms ( http://en.wikipedia.org/wiki/Lego_Mindstorms ), for example, can easily do what I want but it is too expensive and too complex for my needs.

I'm fine with buying some cheap device and picking it apart to get what I want. I've thought about buying and dissecting a USB powered fan, but they all have high speed rotation (naturally) and I'm unsure if any of them can be turned on/off from inside the OS rather than by plugging them in/out.

Any suggestions welcome!

posted by nolnar to computers & internet (9 comments total)

I'm struggling to think of anything quite that cheap. A $35 USB controlled missile launcher is the closest thing I can think of that already provides moving motors under PC control (there is a linux driver too, although the site is dead for me).
posted by samj at 4:46 AM on March 19, 2008

What is your background?

Just to be clear, it sounds like you basically want a USB controlled motor, right?

And by "controlled" what do you mean? Just on/off? I've never written a USB driver, but I would imagine you can turn the power on/off with the driver - so if all you need is on/off, your device only needs to be USB powered.

One option would be to buy a USB fan and either replace the motor with a gearhead motor, or add a gear box to the motor. I believe USB provides 5V, so look for a 5V motor. Also, most DC motors are designed to rotate quickly, slow rotation is normally accomplished by gearing them down.

For other ideas google "crapgadget"
posted by nazca at 4:54 AM on March 19, 2008

A USB controller that doesn't require dedicated hardware. The example listed is to a USB powered switch (with ten outputs), should be easy to simplify it to your needs. I think that AT90S2313P controller is about $4.

Just for interests sake, MAKE have an awesome USB connected controller, it's 149$ but has about as many outputs as you'd need. Use it as a general purpose solution, then simplify when you want to start production.
posted by Static Vagabond at 6:38 AM on March 19, 2008

This is somewhat more than you want to pay, but not completely outrageous: Phidgets servo controller.
posted by adamrice at 7:18 AM on March 19, 2008

This character may have what you're after.
posted by ostranenie at 7:23 AM on March 19, 2008

Your suspicion about those usb fans is correct, they're not going to be software-switched. In the old days (when we walked uphill through the snow to school - both ways) we would have done what you wanted with a serial port by setting a line low or high. USB's flexibility makes it not as easy since you no longer can control an entire port.

More complicated than what you need is the Adurino, but all the associated stuff is open source. The motor control component and information is here, perhaps it will be a good learning starting point for you. It's overkill -but- among what it has is motor speed control, so likely there will be some good information there for what you're trying to accomplish if you want lower speed w/o regearing.
posted by phearlez at 7:25 AM on March 19, 2008

Oh, and you might try looking for this answer over on the LadyAda forums. There's a general projects section there and this seems like a perfectly reasonable question to ask.

If you're prepared to pay for it perhaps Limor will make something for you. AdaFruit is her full time job, after all, and particularly if you're willing to subsequently release the design into the wild so people can use it and she can sell the hardware....
posted by phearlez at 7:30 AM on March 19, 2008

Why movement? Any USB device that has a software switched LED can switch a transistor instead, driving a motor off the 5V parts. If you're not familiar with these parts and it sounds scary and electrical, well, the learning curve is more intimidating than it is hard. Buy some kid's beginning electronics kits/books and open a new world of possibility.
posted by -harlequin- at 10:38 AM on March 19, 2008

Thanks for all these great comments! Some scattered replies:

First, just to be more clear, this is a small one of a kind artwork/hobby device that I'm making for myself and so I'm not trying to construct something to later put in production and sell or anything like that. Sorry if I was unclear.

samj, nice find! I could perhaps adapt that missile launcher for my needs. But it is pretty expensive.

nazca, yes some motor that I can turn on/off from software is basically all I need.

As a reply to many other comments, I have no experience at all with actual electronics and I had my mind set on solving this purely on the "mechanical side". From your comments I realize that I might get a solution that is cheaper and that fits my needs better if I only managed to pull off the electronics. But I'm afraid most of that, like the USB controller that Static Vagabond linked to, is out of my league currently. Another problem: I'm in Europe (Sweden) and so some very special electronic parts can be hard to come by here or cost drastically more due to international shipping. That said, if a part is listed in the www.ELFA.se catalog then I can get it since they have a store in my town.

I realize that if I do some basic reading then what seemed so very hard might be not be so impossible after all. But before investing time in that I'd like a better estimation of how complex steps such an electronical solution would actually involve. Is it mostly a matter of buying two large parts (a USB controller and a motor) and solder wires between them at two points and then moving over to the "software side", flashing firmware, installing drivers etc? Or would I need to do more complex soldering, adding several subcomponents and so on? Also, would I need some extra, expensive equipment (apart from a soldering iron)? And more specifically, can you spot components that would fit well with http://obdev.at/products/avrusb/powerswitch.html
in the mentioned ELFA catalog?
posted by nolnar at 4:51 PM on March 19, 2008