Post on 22-Dec-2021
Learning Objective: To explain how computers and computer programs are used in a variety of products.
Programming Pioneers
Simple electrical systems are used in
products all around us. This steam iron uses only
electrical components; there are no computer-
controlled parts inside it.
A thermostat is a device that can control
temperature and switch on or off at a specific
temperature.
The hot plate is heated until the temperature set by the
thermostat is reached; the thermostat turns off the indicator lights, showing that the iron is hot
enough to use.
Thermostat controlled by dial
These products are controlled only with simple electronic components. How do they work?
KETTLE SECURITY LIGHTELECTRIC
TOOTHBRUSH
When the switch is flicked on, a heating element boils
the water. When a thermostat detects the water is at boiling temperature, it
turns off.
The sensor detects movement near the light and
turns it on. A quartz timer (like those in wristwatches)
detects when a certain amount of time has passed,
and turns it off again.
When the button is pressed, the
motor starts vibrating the bristles, and the indicator light turns on. When two
minutes have passed, the light flashes to show that it's time
to stop brushing!
Why do you think this product is
controlled by a computer system? Which of its functions cannot be
performed by a simple electrical system?
Other products, such as this washing machine, are more
complex and are controlled by computer systems.
The washing programmes have complicated instructions which cannot be
memorised or controlled by a simple electronic system. The programmes must be stored in computer memory and controlled
with a computer system.
How do modern computer memory chips work? How do you think they store information?
A circuit board from a modern SSD hard drive. SSDs store
data on memory chips.
How Memory Chips WorkMemory chips store data by setting thousands, millions or even billions of tiny switches (called
transistors) in on or off positions. The changes in the level of electrical current flowing through the open
or closed switches can be read and interpreted. Can you work out what three-letter word is being spelled out by the three switching circuits below?
Switch state (open = 0, closed = 1)
Corresponding letter
i. ii.1 0 A
0 1 B
1 1 C
0 0 D
Did you work it out? Modern microprocessors and memory
chips contain millions or even billions of tiny transistors. They're hard to see, even using
a microscope.
How Memory Chips Work
AC B
By Pauli Rautakorpi (Own work) [CC BY 3.0 (http://creativecommons.org/licenses/by/
3.0)], via Wikimedia Commons
T h i s t ra f fi c l i g h t i s monitored and controlled by a computer system. Normally, traffic lights A and B are green, unless a car approaches traffic light C, which has a sensor for detecting approaching cars.
A
B
C
Can you write a set of instructions which explain how this traffic light system
might work?
Were your instructions
similar to these?
1.Traffic lights A and B are set to green. Traffic light C is set to red.
2.If the sensor on traffic light C detects a car approaching, a ten-second countdown timer starts.
A
B
C
Were your instructions
similar to these?
3.After ten seconds, traffic lights A and B change to red.
4.Once traffic lights A and B have finished changing, traffic light C changes to green.
5.A twenty-second countdown timer starts.
6.After twenty seconds, the lights will all change back to their starting setting.
A
B
C
Devices such as these are too big, expensive and
unnecessary for systems like traffic lights! Instead, microcontrollers are used.
Embedded computers in systems like those traffic lights don't have touch screens, mice
or keyboards like the computers and devices we're used to using.
Microcontrollers are small, inexpensive computer systems on chips. They are usually designed and built for one specific purpose, such as controlling a
traffic light system. You may have small devices, with microcontrollers on them, at home or at school, which you can program yourselves! Arduinos
and Raspberry Pis have microcontrollers on them. You can connect screens, mice and keyboards to them to program them.
Arduino UnoRaspberry
Pi
Microcontroller
Some products which are monitored and controlled by microcontrollers may be designed, prototyped and tested on a breadboard (bottom-left).
The programmer writes a set of instructions in human language, then turns those instructions into an algorithm written in computer code which the
microcontroller understands (centre). The final design is made on printed circuit boards (PCBs). The program is stored
on a microcontroller on the PCB (bottom-right).
The traffic light instructions, or algorithms, you wrote are similar to the one written by the
programmer who programmed the microcontroller embedded in the traffic light system. Another way of
showing instructions or algorithms is with a flow chart.
START Traffic lights A and B are
green; traffic light C is red.
If the sensor detects a car approaching, a 10 sec.
countdown timer starts.Lights A and B change to red.
At the end of the 20 sec. timer, the lights change back.
A 20 sec. countdown timer starts.
When lights A and B finish changing, light C changes to
green.
Do you think you could write instructions or draw flow
charts showing how you think other products with embedded
systems are programmed?
GlossaryQuartz - an electronic component called a quartz oscillator is
used to measure the passing of time in a circuit. When a tiny electric current is passed through a microscopic quartz crystal, it vibrates. Simple electronic circuits such as those in security lights
count the number of vibrations, then turn off the light.
Did you know that quartz crystals vibrate exactly 32,768 times a second?!