I was looking for hackable electronic toys at the local thrift store. The dolls were nearby. I couldn't avoid them. There were hundreds of them, strange limbless torsos and disheveled Barbies lying in twisted entangled piles.
One bald head --- just the head --- sat alone on the top shelf.
As I walked past it the doll's eyes fluttered, then suddenly snapped open in an unfocused stare. I freaked out... until I realized the vibrations from the nearby pillaging children were causing the eyes to operate. I was relieved and decided I had to have it. For 50 cents, how could I resist?
It turns out that the eyelids are on a pivot. A metal weight holds them shut or opens them depending on the head's orientation. However, the weights are so delicately balanced that any small vibration (or magnetic field) can cause them to flutter, or even snap open unexpectedly.
I needed to learn to control this frightening phenomenon. If I can control it, I take away its power over me. (And can frighten other people instead). A cheap RF remote-control, some motors and LEDs gave me some ideas.
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| Schematic circuit diagram for making a creepy Halloween doll head prop with cheap RF remote controls. The LEDs cause the skull to glow. The small vibrator causes the eyes to flutter. The big motor was intended to make the head spin on a spiked pedestal, but I might replace it with an electromagnet to pull on the metal weights and make the eyes snap open suddenly. |
I have posted about how easy these cheap RC units are to work with, but didn't include any real examples. So I worked up a quick breadboard example in Fritzing last night. I haven't hooked it up yet, so there are probably errors in the circuits (I just did the diagram to help me think about how to do the project). But it gives you a good idea of the kinds of things you can do with a $10 radio remote control.
The items used in the schematic are available from Amazon.
The doll-head's pale, unnaturally pink skin is partially translucent, so an LED causes the skill to glow eerily from within. I'm using red and green LEDs for a nicely diffused sick glow. I pull the power directly off the RC receiver's pins with a current-limiting resistor placed inline.
The small vibrator also pulls power from a receiver pin. I used an NPN transistor and protective diode to form a basic motor driver circuit. It causes the eyes to flutter (but not open) and is startling because, well, doll heads don't typically buzz and vibrate. (Or maybe they do, how would I know)
The big motor needed a driver board and extra batteries. I was originally going to put the head on a pedestal and have it spin. (Fun, fun, fun) But after working on a gearing system and stand, I started to think of other options.
Right now, I'm thinking about using an electromagnet to pull on the metal weights of the eyes. They should snap open quickly to great emotional effect. And the small ones only need about 5v, so the extra batteries and driver-board might not be needed.
I'll work on this and put an example out for some of my friends to experience. I'll let you know what happens.
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