FOR THE SETUP AT HOME:
Net-connected computer It’s helpful if it has
Soldering iron or wire-wrapping tool RadioShack
part #64-2802 or #276-1570. Wrapping wire
around component leads is less permanent than
soldering, but it’s OK for prototyping.
30-gauge wrapping wire RadioShack #278-503
Photoresistors, 5-pack RadioShack #276-1657
2N222 NPN transistors, 15-pack RadioShack #276-
1617. Or use relays for higher-powered devices.
Solderless breadboard RadioShack #276-003
Devices, DC powered that you want to control
DC power supplies with voltages that match your
devices. You probably have some spare wall-warts from appliances you don’t use anymore.
Cardboard box (optional) but recommended, large
enough to hold your computer screen
FOR THE REMOTE LOCATION:
Webcam that you can move and point (i.e. not built
into the screen)
Dark, flat surface
Build Your Web Chat
Time: 1 Hour Complexity: Easy
Set It Up
NOTE: You may need to insert an additional transistor/
relay for higher-powered devices.
58 Make: Volume 22
Then test whether the switching works for each
device by covering and uncovering the photoresistors with your hand.
Use electrical tape (Figure B) to tape the photoresistors sensor-side down on the computer screen,
spaced apart (Figure C, following page). Adjust the
screen brightness to a level such that the devices
switch off when the screen is black. With some
circuits, I found that I had to put a piece of paper
between the photoresistor and the screen to reduce
the light. I recommend also putting the computer
screen in a box to exclude non-screen light that
could interfere with the sensor readings.
Set up your devices however they’re going to
work. It helps if your home computer has a webcam
pointed at the devices, so you can remotely watch
At your work computer, connect a webcam and
set it up so that it looks at a dark, flat surface. I used
a PVC stand that I’d already made for the camera
and pointed it down onto a black T-shirt (Figure D).
Illustration by Julian Honoré/ p4rse.com; photography by Lee von Kraus
Establish the Connection
On your work computer, run Yahoo Messenger. Next
to your home username, select View My Webcam to
open a webcam feed, then leave it running.