Page 86 - 15 Dangerously Mad Projects for the Evil Genius

Chapter 5 ■ Balloon-Popping Laser Gun 65

Figure 5-30 The lid to the can jumper

light. If it does not return without you putting your
finger over the sensor hole, you will need to take it
apart again and reduce the sensitivity a bit.
You are now ready to use your can jumper. You
may find it amusing to place the can near one of
your minions and, while out of their sight, activate
Figure 5-29 The can with the board fixed the can with your laser gun. For best results, select
in place
a minion with a fear of the supernatural.

micro-switch in the “on” position. If the card has a
black side, this should be on the inside of the lid.
Theory

Testing the Can Jumper In this section, we take a look at some of the
technology behind this project. In particular, we
With just a small hole to allow ambient light in, look at the two types of transistors that we use.
the can is going to be quite dark inside, so you
First, we look at MOSFET power transistors
should be able to set the sensitivity to maximum. It
used to switch big loads like the the motor, and
is best to adjust the sensitivity with the board
then we look at the phototransistor that we use to
outside of the can as it is difficult to access the
trigger the MOSFET.
variable resistor when inside the can.
Maximum sensitivity means the variable resistor
MOSFETs
should be in its most counterclockwise position. So
set it to that and confirm everything is okay by MOSFETs (Metal Oxide Semiconductor Field
pressing the micro-switch. Unless you are working Effect Transistors) are a type of transistor that is
in the dark, the arm will fly up. Now reassemble excellent for switching high currents. When they
everything and put the lid on. The can jumper may are turned fully off, they have a huge resistance,
activate as you put the lid half in place, but you and when they are on, they have a very low
should hear the arm return to its resting place resistance. This means that they generate very little
when the lid is fully in place and blocking out the