Setting Fires With Electrical Timers

WARNING: Be sure to place the wires on the correct side of the kitchen timer. If the numbers
are painted on the rotating dial instead of on the body of the timer, then things can get confusing.
In this situation, move the rotating dial to have it point to zero (there should be no ticking). Now
the number 51 on the rotating dial will indicate the location of the 9-minute mark on the body of
the timer, where one wire should be taped in place. The number 50 will indicate the location of
the 10-minute mark, where the second wire should be taped in place.
Step 3: Strip ½ inch of insulation from the ends of both wires on the 9-volt battery-snap.
Step 4: From the spool of wire, cut off a 12-inch (30 cm) piece. Strip ½ inch of insulation off one end and solder
it to either of the two battery-snap wires. The other end of
Figure F: Close-up of one wire taped to kitchen
this 12-inch wire will go to the igniter and is known as a timer. Notice how it makes a 90 degree bend to
“firing wire.”
allow the tape to grip the wire more securely.
Step 5: From the spool of wire, cut off a 6-inch (15 cm)
piece. Strip ½ inch of insulation off one end and solder it to
the other battery-snap wire. Strip 1¼ inches of insulation off
the other end of the 6-inch wire and tape it to the body of the
kitchen timer at the 10-minute mark. Secure it firmly with
three strips of tape and a sharp bend as shown in Figures F
and G.
Step 6: Attach male bullet connectors to the loose ends of
firing wires #1 and #2.
How It Works:
As the kitchen timer winds down, the matchstick on the
rotating pointer will push the two wires together, thus
completing the circuit. The 9-volt battery is then able to send
electricity to the igniter. One of the wires should have a bend
or kink in it to ensure that the wires will touch each other and
make a good connection. The two wires are placed near the 9
and 10 minute marks because some kitchen timers are
pathetically weak as they reach zero and don’t always have
enough force in their spring mechanism to push the wires
together. Positioning the wires away from zero (i.e. the 9 and
10 minute marks) reduces escape time but significantly
improves reliability.
The sharp bend and the multiple pieces of tape keep
the stripped end of the wire from moving when the
rest of the wire is shifted or bumped. One strip of
tape goes vertically and two strips of tape go
horizontally.
The Finer Points of Construction:
The success of this timer hinges on the matchstick being able to push the first wire into the second wire. Build
a sample timer and observe closely how this happens. By paying attention to fine details of construction, you can
make the first wire less rigid and better able to move freely:
• The tape should be kept further back on the timer body (at least ¼ inch away from the edge of the timer
body).
• The wire is stiffer wherever it has insulation on it. Strip enough insulation off the end of the wire so that the
insulation stops where the tape stops. In other words, the wire should be bare starting at the point where it
exits from under the tape.
• The wire becomes stiffer as it becomes more twisted. Keep just a slight twist in the wire to hold the strands
together.
• The diameter of the wire must not be too thick.
Here’s another detail that will help the matchstick push the wire: When gluing the matchstick to the rotating
pointer, tilt the matchstick at a slight angle so that its tip is elevated above the body of the kitchen timer. The goal
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