Low Voltage Solenoid or linear Actuator

[quantumplasmathingie]

Do any of you extremely clever fellows know where I could get a miniature solenoid or micro actuator that fits the following constraints:

.5" to .75" travel
9V or lower
1" high housing (or smaller)
Preferably a push, but a pull solenoid might work too (would require some re-engineering).
?

The project is the old AMT snowspeeder. The application is to raise the breaking flaps. I think there just might be enough space under the hull to shoehorn a 1" box or tubular housing in.

I'm hoping such a tiny solenoid exists off-the-shelf already. I've hunted high and low, but most electronic supply sites seem to deal with 12V or 24V solenoids only, and with housings that are too large.

I've thought about using nitinol muscle wires to acheive this effect, but I'm doubting that the material contracts enough to raise the flap sufficiently. "Training" the material seems arduous, and I'm also concerned that the wire will stretch and become less effective after repeated cycling.

Any information or ideas is, as always, greatly appreciated!

-QPT

[Kylwell]

Most the solenoids I've delt with used a capacitor to trigger them, thus able to use a low voltage source to trigger a higher voltage unit. Some where around here I've got some smaller solenoids but they may be too big for your needs.

Have you tried Mouser & All Electronics?

SciPlus

SmallParts

[macfrank]

You could also use a small servo motor (from an RC plane) and with the proper linkage get the same results as a solenoid. Plus servos are much easier to control than a solenoid.

[quantumplasmathingie]

Drat, that first linear motion slide looks to be the perfect size...but at 89 bucks apiece rules it out as a possibility.

Since the load is only a few grams, I might be able to underpower the solenoid. I would like the brake to stay raised as long as the pushbutton switch is closed, so I'm not sure if driving it with a capacitor would result in that effect.

I'm going to experiment a bit with some solenoids that I pulled out of some device or other that I ripped apart, just to see if I can underpower them. They're all too large, but at least I can figure out my power requirements.

If I can't find a prefab component anywhere (with a reasonable price), I might break out my fly-tying apparatus and attempt to wrap my own coils around fine plastic tubing and use a pin as the plunger core.
Last night, I extracted the coils from earphone speakers, and managed to tease the end of the wire loose. I'm a little insecure about whether or not I can handle these tiny-a** wires without scraping the insulation off. I have some other small motors and speakers around that I might cannibalize for a slightly higher gauge of wire if the earphone wire proves too difficult to work with.

Thanks for the leads and the feedback!

[quantumplasmathingie]

Oh, and MacFrank (said with a strong scottish accent, like Mahkfrrrehnck!), I think you're absolutely spot-on with the servo idea. I've dug around and found that the Futaba HT-micro servos are just about the right size and operate on 4.8V! They're only about 14 bucks a pop, so these will pretty much do the trick! With some careful positioning of the servo horn, I won't even have to build a lever system to transfer the motion...which I was considering as a necessary evil if I went with a solenoid, simply due to the limited space. I might even be able to control the rear flaps simultaneously.

http://www3.towerhobbies.com/cgi-bin/wt ... XNCV6&P=ML

I had mentally blocked out servos, because I thought the cost would be prohibitive. You can imagine my surprise when I discovered how cheap they are!

The additional plus, is that the flaps will raise more slowly than with a solenoid, and have that motor-driven feel (well...because they will be). I was guessing that the solenoid would just snap the flaps open.

These should just about squeeze in alongside the cockpit tub. If I'm careful, I should have plenty of room in front of the servos for the lighting modules and the sound effects chip and speaker.

My next big problem to figure out, is how I'm going to hide all the pushbutons and rocker switches that control all the stuff.
I'm planning to have all the electronics integrated into the craft, so that the nephew can actually play with it, and not have the speeder just sitting on a stand.

[Balok]

Don't servos have stepper motors and need a pulsed current. I'm wondering because I'm scavenging an old crummy RC car to run a ship model and the steering element that ran the car steering is bad. It outputs a constant 6VDC, alternating directions as you use the controller. Can I run a servo with the pulses from a 555 or 4060 going either right or left depending upon which of the three wires I use? I assume the black is the Futaba pic is a ground. Hmmm...

[macfrank]

Don't servos have stepper motors and need a pulsed current.

Nope. A servo is just a DC motor (and gearing) driven by a frequency to voltage circuit. Depending on the frequency you send to the servo, you get either no motion, or deflection in one direction or the other. You can use a 555, but there are probably better circuits out there.

[Balok]

Well, that's welcome good news. Thanks as usual Frank. I'll pick one up and solve my little problem. Since the Yamato is for my nephew and his friends to sink, I can afford the $14 servo. Gotta hand it to you Frank, your advice is often my departure point for new forays into techniques and electronics.
Incidentally I'm hatching a plan for an even bigger tracking telescope with some advice from the Chabot Telescope Maker's Workshop. I want to build a 24" or something in that range, offset, large focal length maybe F8 or something like that, a real stout challenge. The mirror size and F# may be limited by the length of the testing room however. Gotta save up for that blank. Man, life is good with such projects.

[MSW]

This begs the question. What did ILM do to operate the air brakes on the snowspeeders?

I mean they are filming with motion control cameras, so the brakes on the models had to function at a precise time and speed during each shot. Computer controlled stepper motors seems likely, but wern't they too large at the time (1979 - 1980) to fit into the snowspeeder models? Or did they mount the control mechanism to the support stand and connect it with cables or some other mechanical means to operate the air brakes?

Of course with so much of the films effects being stop motion, maybe they did it that way?

Just curious is all

[Balok]

Yeah I wonder. My guess is pneumatic. Some guy blowing on a tube. I'm probably wrong though.