A fully "OPERATION-al" Halloween costume
Inspired by the original created by Felix Jung (http://www.avoision.com/portnoy/2004/october/29.php) in 2004 and somewhat by Jack W. Bell's take in 2005 (http://jackwilliambell.livejournal.com/86072.html), I took it upon myself to reproduce it this year with the addition of the mask and light up nose, hence the “Take 3”.
Step 1: THE CIRCUIT
The switch would be metal kitchen tongs (Felix’s idea) with the circuit completed by the flashing surrounding each hole. Each hole then connected together. Everything worked fine but I was disappointed with the fact that if the flashing was only barely touched, then LED and buzzer were feeble. I wanted a steady buzzer and LED no matter how lightly or briefly the flashing was touched. A little research led me to an IC, specifically a 555 timer in a monostable circuit. My favorite site was http://www.kpsec.freeuk.com/555timer.htm. They have excellent descriptions and examples of 555 timer circuits. Or try this one http://www.uoguelph.ca/~antoon/gadgets/555/555.html. So the circuit grew (see image 2).
To help determine what size capacitor and resistor to use for the timing circuit try the following program http://www.doctronics.co.uk/down555.htm. I went with a variable resistor (a 1Meg Potentiometer) so I could play around with how long the buzzer and light would go off. The 6V was 4 AA batteries in a case I picked up at Radio Shack. After putting everything together on a breadboard (it worked!), I tried my hand at soldering. Only two attempts to get it right. Image 3 is a shot of the circuit board.