thoughts on a circuit for Halloween hand

[LeftHandRobotics]

Hey guys I'm extremely new to this, new enough that all I've really been able to study are the parts and functions that make up the circuits.  I had an interesting idea, I'm hoping I can share it with you guys and not get ripped off.     It's pretty simple but I thought it would really be cool.  I'm pretty good at making silicon molds of things like body parts and what not.  I thought it would be cool to make a realistic looking hand with a few motors.  The hand would sit in a jar of dirty water, and the idea is that around Halloween you'd set this out as a decoration.  What I thought would be cool, and will need help for this, is to rig it up on some sort of sensor time delay so when an object (person) moves within 3 feet of it, and remains there it powers the motor in the hand that make the fingers wiggle.  The idea is that someone would see the hand and come in for a closer look, once they've been looking at it for say 4-6 second (enough to get real close and see if its real or not) then the fingers quickly wiggle and scare the Bejesus out of you.  Thought it would be cool to make, I'd buy one!  of course I have no idea how to make the circuit, although it sounds simple enough.

Thanks guys,

Lefty

[random robots]

okay so what you do is you have a sensor to detect the object. the output of the sensor would go to a capacitor which would then go to a resistor that goes to ground. the capacitor would also go to a diode which would go to an inverter which goes to a circuit that is exactly like the circuit above that lasts for as long as you want the motors to be on which would go to the output which turns on the motors. you control the timing for the RC+diode circuit with the formula R times C= time delay. so its sensor to a time delay signal blocker to an inverter to another time delay signal blocker to the motors. of course you can also program a microcontroller to turn it on as well. so the code would be wait for if sensor input = on, wait 4 seconds. if sensor input still = on, turn on pin_____ for_____ seconds.

[random robots]

also, you shold connect the output of the sensor to the gate of an SCR which controls the circuit's power supplies so it won't turn on as soon as you turn the circuit on.