# Random on/off



## Revenant (Mar 17, 2007)

I was wanting to do one of those 2-axis motorized head thingies, but I had a thought: If the two motors would cut on and off in a semi-random or seemingly random fashion, it would give a more random look to the directions the head moves, instead of a constantly repeating loop of movement. Sometimes it would nod up or down, sometimes it would turn, and sometimes combined. I'd be using DC motors. So....

What would the most affordable way be to make a DC circuit that would cut and restore power to the motors?


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## Otaku (Dec 3, 2004)

Hmmm. Using two 555 oscillators with different on-off intervals can give the look of a random movement. You'd have to watch it for a long time to see any repetition of the sequence. Easy to build.


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## Revenant (Mar 17, 2007)

'kay...

Where do I find the circuit so I can build it?


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## Hallowennie315 (Sep 5, 2007)

what a bout a flicker circut.... would that work.....? I was actually thinking of doing that too!


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## Otaku (Dec 3, 2004)

Revenant said:


> 'kay...
> 
> Where do I find the circuit so I can build it?


Here's a good place to get the circuit you need. Build two 555 astable circuits, each one controlling a relay that switches power to one of the motors. Using fixed resistors or pots, adjust the on-off intervals to get a pseudo-random movement.

http://home.cogeco.ca/~rpaisley4/LM555.html

As far as using an AC flicker circuit goes, I've never tried it (yet), but I don't know what it would do to the power supplies. You would get a really choppy movement, I think.


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## TommaHawk (Sep 18, 2007)

Um... you could do the low-tech thing they sometimes do for "eyes in the bushes": put a metal can on a slow motor. Splice the power to your motor to this can, thus electrifying it, and have the lead to the motor rub against the outside of the rotating can. Haphazardly put tape or paint splotches or rubber cement or something on the shell of the can, so every-so-often the contact is lost as the rubbing-lead drags across the tape (killing the power to the motor). Have both of your motors touching different parts of the can, or use two cans - this way each motor will seem to run independently.

There's a good link for this technique out there somewhere - it might be on the Monsterlist.
Ah - here's one: http://www.minionsweb.com/eyes.htm


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## Revenant (Mar 17, 2007)

I was going to use cams to trip switches to the motors, but I changed my mind and decided to go the microcontroller route with a couple of relays. I can do it for under 25 bucks and I have to drag me arse into the 21st century sometime anyway heh might as well be now. Then maybe I could even synchronize the lighting with it all in one package.


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## SpookySam (Mar 27, 2007)

If you're using 12V, you could try using a blinker fuse from your Automotive store.


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