le_chiffre

Hi. I'm searching for an actuator or some kind of motor, that has only two positions. What I'm looking for is a very small device, that allow me to release a very small compressed spring when a small current is applied. (kind a circuit breaker, or something like a relay). It has to be small, and cheap. I don't know how this devices are called (i believed they are "actuators"), therefore I cannot google it, , so I'm asking here.

Do you know anything like that? how expensive they are?

thank you very much

Hank Fletcher

You might try searching for "solenoid," they have plenty at electronics goldmine surplus, inlcuding a pinball mechanism, if I recall, which seems similar to what you've described.

I'm kind of in the same boat as you right now, I think, with an application I'm working on. I should warn you to save you the trouble I went through that using solenoids require more current than, for instance, a DC motor would for equivalent power output. For that reason, I'm considering using a gearmotor instead and just converting the rotary power to linear to suit my mechanical needs. With a gear ratio that's fast enough for your application, but high enough to hold in the two positions you've described, it might be an option worth considering. Take a look at the recent thread I started about the tamiya motors in this part of the forum to get an idea of what I'm thinking about.

If this doesn't suit you, is there anything more you can tell me about your application?

le_chiffre

Thank you Hank.

Have you seen those ballpoint pen that have a mechanism for retracting the tip?

http://en.wikipedia.org/wiki/Image:Ballpoint-pen-parts.jpg

That's exactly the kind of action I'm looking for, the only difference is that I want to release the spring using a small current: The user of the device push down a key/switch (smaller, lighter, than a keyboard key). The swicth compress an spring and get stucked by some mechanism. When I want to release the switch, I make a small current run through something and voila, the spring releases and the switch go back to normal position.
Because I want to have a lot of this, in an small area, I want it to be cheap, simple, and if possible, with low consumption.

Thank you very much

Hank Fletcher

What you've described seems identical to power locks on a car. Is that right, but you want them on a scale about the size of pen instead?

How many do you need?
How fast do they need to switch from one position to the other?
What's your budget?
Does it matter how loud it is, that is, can it be as clicky as a pen?

How about this doodad?
http://www.solarbotics.com/products/gm10/
It looks like it presses forward, and then returns with spring. You could modify the actual mechanism from a cheap pen to serve your purpose, and use this thing to tap the end to switch positions? Looks like you'd just have to put power to it briefly when tapping the pen, and it wouldn't be using any power when idle.

Hank Fletcher

Just had another thought that's kind of related to your interest. Recently I was fixing some trumpets, and the pistons on trumpets are returned to their open position with springs. The problem with these trumpets is that the springs had somehow become more stiff, I think with age and oxidization, so the pistons were harder to press down, and returned to open quite fiercely and with a bit of a clunk.

If you find that the springs in your pens are the same way too hard to compress, you might try tinkering with them a little bit. It should only take a very light spring to return a pen mechanism, and no doubt many of them are sold with tighter springs than need be. Just something you might consider when you're shopping around in the stationary shop for pen options. A lighter spring will mean less of a power/tprque requirement from your motor, allowing it to be smaller and/or more efficient.

Hank Fletcher

Tinker with the spring in your pens. Lol.

le_chiffre

Thanks Hank

A lot, maybe 100
[quote] How fast do they need to switch from one position to the other?[\QUOTE]
mmm, I don't know, < 1 sec
I don't have one, but I was thinking in some mechanism that each one of this retracting parts costs as most 1 dollar... I'm not sure if I'm dreaming here, but that's what I was looking for
Yes, it can be as clicky as a pen
Thank you, but the price is prohibitive!

I will tell you what I need this for, I have no reasons to keep it secret. I thought it could be cool to make an Electromechanical Go Board ("Go" is a chess like chinese game
http://en.wikipedia.org/wiki/Go_%28board_game%29 ). Instead of placing stones I think that the board could have some kind of rotating tri-side piece, with each side with a different state (space/white stone/black stone) printed or something like that. It's nice to play Go in real boards instead of computer display, but to count spaces and stones is boring and you can make mistakes... So I thought that with an electromechanical go board, you could have a microcontroller do all that stuffs and automatically spin the tri-sided piece if it happens that that space has been conquered.I want the pen mechanism to spin this tri-side pieces: when a player want to put a white stone in some space, it spin manually this piece. When the black player eats this stone, the microcontorller automatically spins it back to the normal state. Plus, watching the rivals stones disappears with a pen-like click could be great!
The thing is that Go board has almost 400 spaces (19x19)!!!! Thats a lot of tri-sided pieces!... Neveless, you can play Go in a 9x9 board (81 spaces) ... so thats why i want it to be very cheap, and simple and small (you must pack together 81 pieces).
There are some electronics boards that uses LEDs, but I'm not interested in that solution... this is simple an idea I had some years ago, and I just remembered today.

Thank you

Thanks again

Hank Fletcher

Sorry, I haven't had much of a chance to read up on the game yet, but I think you might be going about this a bit excessively in terms of parts. How many pieces have to be turned at any given time? Is a rate of one piece per second acceptable, or is it that lots of pieces will have to be turned all at once?

It seems to me that the more economical solution would be to build one flipping device, and move it around to the piece that needs to be flipped. Someone recently posted a link to an easy, low cost CNC router video on youtube. Go to youtube and search for "easy CNC" and watch the video. Consider that you might be able to convert the X-Y axis alone to move your piece flipping mechanism. That seems like a solution that could only cost somewhere in the $25 to $50 range, plus your efforts, of course!

Here's the video I was referring to:
http://www.youtube.com/watch?v=6drMZqmyXQc

le_chiffre

Nice video, but I think that to build a XY robot arm is too much for what I had in mind. It could work in a slow way, but I think it would be a diferent project. Anyway, it's an interesting concept.
Maybe what I'm looking for doesn't exist, but I wiil keep searching some more time.
Maybe I could use this motors....
http://www.pagermotors.com/Products....category=Pager

Although $1.50 each still is expensive!

Thanks again

toy4crawlin

pretty amazing mini actuators , many applications and RC hookup
http://www.robotshop.ca/home/product...-298-06-I.html

toy4crawlin

Hey guys, I'm all new here to this great looking forum.

I have been doing research for my crawler project, thought you all might like these.
they come in many configurations



good luck to you

Ri

toy4crawlin

try Firgelli or servo city

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The Mad Professor

Old cell phones (or pagers) might yield a solution, those that have the ability to vibrate when a call is received. This is achieved by the use of an small electric motor that may be suitable for miniature robotics applications.

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It may seem like a good idea at the time , but never stir your cold coffee with a soldering iron.

Mikebits

Good idea kinda like those old electric football games, but in this case the piece vibrates instead of the board.

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h-tone

You should look into muscle wire. It's a wire that contracts when a current passes through it, and then can be stretched back with a spring (or another piece of muscle wire pulling the other way like a see-saw) You can get spools of it. Check out the inchworm robot on youtube.