I started out first experimenting with the aluminum flashing. Previous costume creators used electrical boxes and aluminum foil. I thought aluminum roof flashing would be perfect. I picked up a 6V piezoelectric buzzer (Radio Shack) and a 10 Candela LED (Fry’s) and was off and running. Since my electrical engineering knowledge is wanting, I found these sites helpful for dealing with the LED http://led.linear1.org/1led.wiz
See image #1 for the original circuit diagram I was going to use.
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.