I saw the featured Bare Instructable on building paper houses with a painted circuit that lights the house up in the dark.
Christmas was a few days away, and I was thinking of making something for the two grandkids that we could work on together. They love art projects, and so decorating the finished houses seemed like a great idea.
I had bought a container of BARE conductive paint from Sparkfun with the idea of making interactive popup pages. I didn't have much luck in my initial tests, so I just shelved the project.
I checked out Sparkfun and the paper house kit is about $20; I thought I could whip something together myself.
Step 1: Materials
I set up a breadboard with the components. Neither transistor worked with the circuit design given. After some fiddling around and experimenting, I came up with the circuit shown in the photo.
There are several variables which affect the circuit: the photoresistor you are using, the thickness of the paint, the leds you are using.
However, using a 10K trim pot seems to give a wide variance in adjusting the sensitivity correctly.
Here's my parts list:
10K-Ohm micro-size potentiometer #271-0282 $1.69
9V battery snap connectors(5) #270-0325 $3.69
Cadmium-Sulfide photocells(5) #276-1657 $2.99
2N3906 transistor (15) #276-1604 $2.99
LED - use 2 - Radio Shack sells various kinds
cardstock to print on
a self-healing cutting board is nice
cardstock or paper that fits in your printer
ballpoint pen - a dead one works great to score the folds in the paper
snips or scissors to cut leads on parts
Tacky Glue or UHU stick glue
a small screwdriver to turn the micro potentiometer
I have included the pdf designs on this page for download.