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[on:]

So, my fiancee and I are pretty big into Halloween - every year, the party gets a little more extreme; more decorations, bigger, badder, etc... last year we had a live dj! anyways

we're getting to the point where we've started purchasing actual animatronics from Spirit Halloween store and the like; which are cool, but at anywhere from $200 to $300 a piece their kinda lame in what they actually do; ie: just flashing lights or some sounds...

Anyways - kinda just looking for idea's on servo's - i got my decimilanova in the mail the other day - made sure it worked, got comfortable with the language (looks like php to me, as it should being based on c), played with a servo from a old gas RC car i had - very cool

posted this to facebook, someone suggested i make a frankenstein monster

i guess i'm asking - servos turn anywhere from 0 to 360 for the continuous ones, motors are stronger and provide more force.

how would you build something that pushes? like, a monster thats holding his head with his hands and lifts the head off of the body ? (i have one of these) - that lifting mechanisum - what is that? is it a servo with some plastic / metal pieces that produces a lifting motion? i'd open it up, but its covered in finished latex and i'd have to cut it to get to the internals - a piston i guess i'm describing - but i havent been able to find anything like it for small projects like this

obviously weight is an issue - for the monter i think i'd use newspaper to give the body depth and keep the motion down to a minimum - hinge at the hip and sholder...

any thoughts?

-Mario

[Reply #1 on:]

Windshield Wiper motor from the junkyard with carefully positioned switches for feedback?

http://www.scary-terry.com/wipmtr/wipmtr.htm

Would be an expensive servo solution, I think.

[Reply #2 on:]

You can buy servos with a huge range of torques, depending on your needs.

To turn rotational movement into linear movement you can use a simple slider crank mechanism (piston). Here is an example in wikipedia.
http://en.wikipedia.org/wiki/Multibody_system

You wont need it to rotate more than 180 degrees to get the full linear movement so a typical servo will work (not continuous rotation).

[Reply #3 on:]

Sometimes called a solenoid by industry, what you are looking for is an actuator.

You'll need a motor driver for it, but if you head to your local Wally World or Princesses Auto, you can usually find a "Door Lock Actuator" kit that will include a keychain FOB, receiver and 4 12V actuators.  Pulse the 2 wires one way, actuators push outwards.  Reverse polarity and they pull inwards.

That will give you a few inches worth.

If you need extreme linear movement, usually hobbyist level pneumatics are the key.  I've seen a few props powered this way.  Air is released into one tube that slides over another.  Most roaming carny "funhouses" use this technique, hence that unique sound common to all of them.

[Reply #4 on:]

Also a stepper motor turning a threaded rod material and nut type travelers can make for a low cost, high torque, long linear travel actuator. You can use limit switches at both desired end of travel positions or just a home position switch and use open loop software to determine desired travel (count steps).

Lefty

[Reply #5 on:]

thanks guys - this helped a lot

[Reply #6 on:]

http://www.firgelliauto.com/default.php?cPath=110

found this when i searched google for "dc actuator"

little expensive - the mini ones look to hover around $60 or so while the bigger ones are around $120 or so (usd)

not entirally bad - the goal is to keep the project under $250 / 300

12 volts dc - if memory serves me right, the servo / motor shield should be able to power that fine with an external power supply

-Mario

[Reply #7 on:]

I like the last video on this page:

http://www.firgelliauto.com/robotics-animatronics-projects.php