Page 74 - 15 Dangerously Mad Projects for the Evil Genius

Chapter 5 ■ Balloon-Popping Laser Gun 53

Cats are much better for testing than dogs,
because most dogs will abandon the chase once
they have worked out that they cannot eat the little
red dot. Cats, on the other hand, will happily chase
the elusive dot around the room for some
considerable time. In this respect, they are
somewhat similar to minions.

The Balloon Popper

In this section, we will describe how to make the
Figure 5-8 The balloon popper
balloon-popping part of the project. If you are
more interested in shooting cans than in popping
The balloon popper has a control knob that sets
balloons, skip this section.
the sensitivity of the sensor, and a switch that can
The balloon popper (Figure 5-8) is a small box be set to “live,” “off,” or “test.” When set to “test,”
containing a battery, a light sensor, and some other the resistor does not get hot; instead, an LED lights
electronics. When light from the ray gun hits the up. This lets you set the correct sensitivity.
light sensor, it turns on a transistor that allows a
The electronics for the balloon popper are
large current to flow through a resistor. The
contained in a plastic box. Most of the components
resistor is fixed to a terminal block and taped to
are mounted onto the lid of the box. Figure 5-9
the balloon. The resistor gets hot enough to burst
shows the schematic diagram for the balloon popper.
the balloon after 10 or 15 seconds.

S1a
Live
Off
T1
Test
S1b
Test Live
Off
6V D1
4 x AA R3

R4
2.2
R2
100
1K

R1
T2
100K

N

Figure 5-9 The schematic diagram for the balloon popper