Hardware Reference
In-Depth Information
Table 13-6
What You
Will Need
QTY
Item
Description
1
Wireless remote kit
his is shown later in Figure 13-11. here are a number of kits
available on the market that consist of a key-fob remote and a
receiver. he receivers are usually 5V-10V and have four digital
outputs. he key fobs vary from one button to four buttons. here
are diferent kinds of receivers (momentary, toggle and latch).
You are using a momentary receiver here (explained further later).
1
5V power supply
Although this is not mandatory because the Raspberry Pi does
have a 5V power supply, I recommend a separate power supply for
the receiver. It is best to not overload the Raspberry Pi, and I have
found that the current required by this RF receiver exceeds that
of the Raspberry Pi, which afects the distance you can get
between the key fob and the receiver. An old cell phone power
supply should work (5V 700mA). Be sure to check the voltage and
current of both input and output in the data sheet of the receiver
you purchase. he output signal voltage should be 5V.
1
PN2222A transistor
Switching NPN bipolar transistor 40V/.6A.
1
10kΩ resistor
Brown, black, red, gold.
2
1kΩ resistors
Brown, black, orange, gold.
1
Solderless breadboard
A prototyping board for which parts and wires can be connected
by clipping them into the board. It is used for prototyping elec-
tronics without having to solder parts together.
3, 4
Jumper wires
Male to male for breadboard connections, male to female for con-
necting the breadboard to the GPIO pins. Jumper wires usually come
in packs of various quantities, colours and sizes. Although you need
only 7 for this project, having 20 to 30 of each should see you
through most projects. Any size will do for this project, but shorter
male to male (10 cm) and longer male to female (20 cm) are best.
Construction
Radio frequency circuits are complex and not worth building yourself when they are readily
available prebuilt for a minimal cost (as shown in Figure 13-11). As discussed earlier, there
are diferent types of radio frequency circuits available on the market (momentary, latch and
toggle) that all work slightly diferently. A momentary receiver's digital output will remain on
as long as the key-fob button is pressed. he latch receiver will ensure that only one output
pin is on at any one time. For example, if you press button A, digital output A will go on. If
you press B, A will go of, and B will go on - and so on. A latching receiver digital output goes
on when a button is pressed in and out, and of when the same button is pressed in and out.
In this project you will use a momentary receiver, but you can use any type and adjust the
Python code to suit the type of the receiver.
