Hardware Reference
In-Depth Information
THINK YOU'VE GOT
fast ingers? Find out in this chapter as take your irst steps in hard-
ware interfacing to build a reaction timer. You'll program the Raspberry Pi to wait a random
time before turning on a light and starting a timer. he timer will stop when you press a button.
Welcome to the Embedded World!
For some people the idea that computers aren't always big black or beige boxes on desks is a
surprise, but in reality the majority of computers in the world are embedded in devices.
hink about your washing machine - to wash your clothes it needs to coordinate turning the
water on, keeping it heated to the right temperature, agitating your clothes by periodically
spinning the drum, and emptying the water. It might repeat some of these steps multiple
times during a wash, and has diferent cycles for diferent types of fabric. You might not have
realised it's a computer program. It takes inputs from switches to select the wash and sen-
sors that measure water temperature, and has outputs that heat the water and lock the door
shut, and motors to turn the drum and open and close valves to let water in and out.
Take a moment to consider the number of appliances and gadgets that need to measure
inputs, do some processing to reach a decision and then control an output in response.
A modern kitchen is crammed with computers that watch over and automate our appliances
to save us efort. Computers aren't just embedded in practical products either; they're in
electronic toys and entertainment devices. After working through this chapter and the other
examples in this topic you'll be on your way to designing your own embedded systems to
make your life easier, or entertain you.
Before you get too carried away connecting things up it's worth considering a couple of warn-
ings that will protect you and your electronic components.
Good Practice
Electricity can be dangerous, so it is important to use it safely. he muscles in your body are
controlled by tiny electrical signals, and these can be afected if electricity lows through your
body. Your heart is a muscle that can be stopped by an electric shock.
he low of electricity can cause heating, which will either cause burns to your body (some-
times deep within tissue) or can cause a ire.
Electricity can kill! Only experiment with low voltages and currents, and never work with
mains. If you are ever in doubt, then you should check with someone suitably qualiied.
