Hardware Reference
In-Depth Information
Figure 13-11:
A wireless
remote kit.
his is the irst time in this chapter you have used a transistor. Although transistors have
many uses, one of the lesser-known uses is the capability of a bipolar transistor to switch
things of and on. With the lat surface facing you, the PN2222 transistor has three pins
from left to right: the emitter, the base and the collector. When voltage is applied to the base
the transistor allows the current to low through the emitter (source) to the collector (drain).
You will construct a switch similar to what you did in the section “Project 1: How to Create a
Motion Sensor and Door Switch”, but instead of a door switch you will use the transistor to
switch the Raspberry Pi GPIO when the wireless receiver receives a signal. he reason you do
not connect the receiver directly to the GPIO pin is that it has an external 5V supply and will
damage the GPIO pin, which has a 3V maximum.
Be extremely careful when working with circuits (especially 5V) that connect to the GPIO pins
as they are not protected and you can very easily cause permanent damage to your Raspberry
Pi. Double-check the wiring before powering on the Raspberry Pi and the external power
supply.
