1. Electronic Control Systems
Electronic devices have been developed to make life more enjoyable, easier, safer or more productive.
Some examples:
Microwave oven.
Traffic lights.
Computers.
Games consoles.

2. There are 2 types of Electronic device,
Purely electronic devices such as Digital Watches
Mechatronic devices such as a Video Recorders
Question: Why do you think a Video Recorder comes under Mechatronic devices?

3. Pupil Assignment List three electronic devices.
List three mechatronic devices.
Explain the ‘mechanism’ in each of the three mechatronic devices listed.
Some possible answers:
Gameboy, Television remote control, Calculator
Computer CD-ROM drive, Microwave oven, Remote door lock in a car

4. System Diagram
Both Electronic and Mechatronic devices have one thing in common, they both have a control unit.
The system diagram for a warning device for a freezer in a restaurant would be drawn as below.

5. Transducers
Input transducers are electronic devices that detect changes in the ‘real world’ and send signals into the process block of the electronic system.
Output transducers are electronic devices that can be switched on and off by the process block of the electronic system.
A popular electronic toy is shown. Try to identify as many input and output transducers as you can.

6. Pupil Assignment
List the Input and Output transducers for the following products
Personal Music Player
Vending Machine
Washing machine
Hairdryer

7. Microcontrollers
A microcontroller is often described as ‘a computer on a chip’
It has a memory and the ability to receive inputs and control
outputs
It is a small & inexpensive device
Often built into products to make them more intelligent and
easier to use
Usually programmed for a specific purpose/ product

8. Advantages of Microcontrollers
A microcontroller can often replace several parts or even a complete circuit.
The main advantages to using one are:
Increased reliability
Simplified product assembly (less parts)
Greater product flexibility (can be re-programmed)

9. Pupil Assignment
List three devices that may contain a microcontroller.
Explain why you think it would be useful to have a microcontroller in these devices.

10. Inside a Microcontroller
ROM
Read only memory (permanent)
Contains STAMP operating instructions
Retains this program even when without power
EEPROM
Electronically erasable programmable read only memory
Your program is stored here
The ROM will read this and carry out the instructions
RAM
Random access memory (temporary)
Stores information from calculations whilst running
Is wiped when the power is cut

11. Inside a Microcontroller
ALU
Arithmetic and Logic Unit
The control centre of the Microcontroller
Runs the instructions stored in the ROM
I.e. it can only READ from this memory and not write or send information to it!
Clock
The clock synchronises all of the internal blocks
It sets the operating speed of the system
Buses
Information is carried between the various blocks on buses
These are groups of wires
Data Bus carries data between the ALU and RAM
Program Bus carries data from ROM to the ALU

12. Inside a Microcontroller
IMPORTANT – Input Output port, connects to “Real World”

13. Stamp Controller Programming Procedure:
Draw a flowchart for the control task.
Write the program on the computer using the Stamp software.
Connect the download cable from the computer to the stamp controller.
Connect the power supply to the stamp controller.
Use the Stamp software to download the program.

14. Getting Started - Programming
main:
high 7
pause low 7
pause end
Start up the Stamp software and key in the program.
Save the program and then download it to the stamp controller by clicking ‘Run’.
Your teacher will give you help with the software, if you need it.
In your own words explain what the program does.

15. Pupil Assignment red 10 s red and amber 2 s green
Using the times shown in the table for each stage of a Traffic Light sequence, write a P-Basic Program for the lights then run and test your program.

16. Flow Charts Start / Stop Symbol Input / Output Symbol Wait Symbol
There are other symbols you will need to learn, but we will discuss those when we need to use them.

17. Pupil Assignment
A microwave oven operates with the following sequence. Draw a flowchart and write a P-Basic program for this sequence.
Light on
Turntable on
Magnetron on
Wait 30 seconds
Magnetron off
Wait 10 seconds
Turntable off
Buzzer on
Wait 0.5 second
Buzzer off
Light off
You can decide for yourself which pins to allocate to the outputs transducers

18. Adding Comments
Comments are always added to program listings to help explain the program operation. An example is shown below.
Main:
high 7 ‘switch pin 7 high
pause 1000 ‘wait 1 second
low 7 ‘switch pin 7 off
goto main ‘jump to label main
Note the apostrophe which tells the program that what follows is a comment, not a line of code.

19. White Space
Lets have a look at the layout of the previous code. Note how the code is indented, (tabbed in). This is known as leaving “WHITE SPACE”. White space makes the layout and reading of programs much clearer.
The start of the program is indicated by the “LABEL” main, note the colon after the label. Labels can have any name as long as it is not a P- Basic command.
Copy down the program below and label each part as shown.
White Space
Main:
high 7 ‘switch pin 7 high
pause 1000 ‘wait 1 second
low 7 ‘switch pin 7 off
goto main ‘jump to label main
Label
Comments
Code

20. Symbols Key in the program, then run and test.
Sometimes it can be hard to remember which pins are connected to which devices. The ‘symbol’ command can then be used at the start of a program to rename the inputs and outputs.
symbol red = 7 ' rename 7 ‘red’
symbol green = 5 ' rename 5 ‘green’
main: ' make a label called ‘main’
high red ' red LED on
low green ' green LED off
pause ' wait 1 second
low red ' red LED off
high green ' green LED on
goto main ' jump back to the start
Key in the program, then run and test.

21. LOOPS
main:
high 7
pause 2000
high 6
pause 1000
high 4
high 5
pause 3000
low 4
low 5
low 6
low 7
pause goto main
Sometimes it is necessary to create programs that loop ‘forever’, as is the case in this flowchart. There is no ‘Stop’ symbol because the program never ends!
What command makes the program loop?

22. Pupil Assignment
red
10 s
red and
amber
2 s
green
Draw a flow chart for the control of the traffic lights
Write a P-Basic program using the symbol command to give names to pins
The program should loop
Run and test your program

23. Pupil Assignment
A fountain in a garden centre is to be used to attract visitors to a new range of plastic ponds. The garden centre owner wishes to develop a microcontroller-based system that can be programmed to switch the fountain pump and an external lighting system on and off at regular intervals.
Draw a flowchart for the control sequence and add the missing comments to the program listing.
main: high 7 ' switch the pump on
pause ' wait 10 seconds
high 6 ' switch the lights on
pause ' …
low 6 ' …
pause ' …
low 7 ' …
pause ' …
goto main ' …

24. Pupil Assignment
A toy shop has a train set in the window. The train set has an electric train, a set of red/green signals and a set of moving track points that allow the train to move around two different loops of track. Draw a flow chart and write a P-Basic program to control the train set.
Input
connection
Pin
Output 7
train motor 6
points 5
green signal 4
red signal 3 2 1
Switch the green signal on
Switch the train on for 30 seconds
Stop the train
Switch the green signal off and the
red signal on
Switch the points on
Switch the points off
Switch the red signal off
Jump back to step 1

25. Output Module
Allows output transducers to be connected to the stamp controller
Typical output transducers are Motors, Buzzers and Bulbs
To use the output module, the output device should be connected between the screw-terminal numbered output (4–7) and a V+ connection.

26. YOUR TEACHER WILL EXPLAIN THE MODULE CONNECTIONS
Pupil Activity
Connect 2 dc motors to the output module, enter the following code then run and test your program.
YOUR TEACHER WILL EXPLAIN THE MODULE CONNECTIONS
main: ' make a label called ‘main’
high 5 ' motor A forward
high 7 ' motor B forward
pause 1000 ' wait 1 second
low 5 ' motor A halt
low 7 ' motor B halt
high 4 ' motor A backward
high 6 ' motor B backward
low 4 ' motor A halt
low 6 ' motor B halt
goto main ' jump back to the start

27. Pupil Assignment Copy the flow chart into your work book
Write a P-Basic program to control the movement of the buggy as indicated by the Flowchart

28. Pupil Assignment Build a maze on the table out of books.
Write a PBASIC program to steer the buggy through the maze.
Add comments to each line in your program to explain how it works.

29. Speed Control There are two ways to control the speed of a d.c. motor.
Vary the voltage applied to the motor. Unfortunately the ‘turning power’ (torque) of the motor will also drop, which means the whole motor system will be less powerful.
The second way to control the motor is to always apply the full voltage but then to switch the power supply on and off rapidly. The advantage of this system is that the torque remains quite high.
This method is known as PULSE WIDTH MODULATION

30. Pulse Width Modulation
Motor off is known as SPACE – Larger Space to Mark Ratio = slow speed
Motor on is known as MARK – Larger Mark to Space Ratio = fast speed

31. Pupil Activity
Connect a d.c. solar motor across the ‘V+’ and ‘7’ terminals on the output driver module.
Key in, download and run the program listed below. This program drives the motor at approximately half speed, as the space (off time) is twice the length of the mark (on time).
main: high 7 ' output high
pause 5 ' pause for 5 ms
low 7 ' output low
pause 10 ' pause for 10 ms
goto main ' loop
Try out different speeds (by experiment) by altering the length of the pause delays.

32. Pupil Assignment
Explain the terms ‘mark’ and ‘space’ in relation to PWM speed control of a d.c. motor.
Describe the advantages and disadvantages of using PWM speed control.
Sketch 2 PWM graphs, one for a fast speed and one for a slow speed.

33. Pupil Assignment
The motor on the washing machine is controlled by outputs 6 and 7 (motor B). Switching output 6 on will make the motor turn one way; switching output 7 on will make the motor turn the other way.
Draw a flowchart and write a PBASIC program that will make the motor rotate at full speed in each direction for five seconds.
Write a second PBASIC program that will make the motor rotate at half speed in each direction for five seconds. Use PWM speed control for the motor.

34. For Next Loops
It is often useful to repeat the same part of a program a number of times, for instance when flashing an LED. In these cases a ‘for … next’ loop can be used.
START
SET COUNTER = 5
SWITCH PIN 7
HIGH
WAIT 1 s
LOW
HAVE WE
LOOPED 5
TIMES?
STOP
Note the new flowchart symbol. This is the decision symbol NO ?
YES

35. For Next Loops – Pupil Activity
Key in, download and run the following program.
symbol counter = b0 ' define the variable ‘counter’
symbol red = 7 ' define pin 7 with the name ‘red’
main: for counter = 1 to 5 ' start a for … next loop
high red ' switch pin 7 high
pause ' wait for 1 second
low red ' switch pin 7 low
next counter ' end of for … next loop
end ' end program

36. Pupil Assignment Connect the buggy to the output module.
The buggy should follow the path shown in the diagram, moving in each direction for three seconds.
Draw a flowchart for the movement of the buggy, making use of a ‘for … next’ command structure.
Write a high-level program in PBASIC to control the movement of the buggy as shown by your flowchart.

37. Sub - Procedures
A sub-procedure is a separate ‘mini-program’ that can be called from the main program.
Once the sub-procedure has been carried out, the main program continues.
Sub-procedures are often used to separate the program into small sections to make it easier to understand.
Sub-procedures that complete common tasks can also be copied from program to program to save time.

38. Pupil Activity symbol red = 7 ' rename pin 7 ‘red’
symbol buzzer = 6 ' rename pin 6 ‘buzzer’
symbol counter = b0 ' define a counter using variable b0
main: ' make a label called ‘main’
gosub flash ' call the sub-procedure flash
gosub noise ' call the sub-procedure noise
goto main ' loop back
end ' end of the main program
flash: ' make a sub-procedure called ‘flash’
for counter = 1 to 25 ' start a for … next loop
high red ' red LED on
pause 50 ' wait 0.05 second
low red ' red LED off
next counter ' next loop
return ' return from the sub-procedure
noise:
high buzzer ' buzzer on
pause ' wait 2 seconds
low buzzer ' buzzer off

39. Flowchart Symbol
Sub-Procedure symbol
Your teacher will show you the correct way to draw a flowchart which includes a sub-procedure

40. Pupil Assignment
A washing machine motor should rotate 15 seconds in one direction before reversing and rotating 15 seconds in the opposite direction. This should repeat 10 times.
Draw a flowchart
Write a P-Basic program making use of sub-procedures
Run and test your program

41. Input Module Allows sensors to be connected to the stamp controller
There are 4 digital and 2 analogue inputs
Pins 0 and 1 have a test button, they can be pressed instead of adding switches

42. Digital Signals and Input Transducers
Digital Sensors act like switches
They are either ON or OFF
HIGH or LOW
1 or 0
Some common switches you will meet are the ,
Microswitch
Push and Rocker switch
Reed switch

43. Analogue Signals
Volts (V)
Time (s)
Analogue signals can vary between a maximum and minimum value and depend on the conditions being monitored, for example light or temperature.
Common analogue input transducers are the Light Dependent Resistor, thermistor, (temperature sensor) and variable resistor.

44. More Symbols Microswitch (Single pole, single throw).
Light Dependent Resistor, LDR
Push Switch -t
Push to make
Thermistor
Variable Resistor
Reed Switch
Magnet

45. if-then Command
To enable the Stamp Controller to accept inputs, we need to learn a new command, the IF – THEN command
Connect a switch to pin 0, key in, download and run the program listed below. This program makes output pin 7 flash every time the push-switch on input pin 0 is pushed.
main: ' make a label called ‘main’
if pin0 =1 then flash ' jump if the input is on
goto main ' else loop back around
flash: ' make a label called ‘flash’
high 7 ' switch output 7 on
pause ' wait 2 seconds
low 7 ' switch output 7 off
goto main ' jump back to start

46. Pupil Assignment
A burglar alarm must sound a buzzer and light a warning signal for 20 seconds when any of the 2 windows in a room are opened. Each window contains a reed switch that is connected to the alarm.
Draw a flowchart and write a PBASIC program that will operate the burglar alarm correctly. Use the following input and output connections.
Input
connection
Pin
Output 7
red light 6
buzzer 5 4 3 2
switch 1 1
switch 0

47. Pupil Assignment
As part of a Christmas decoration in a shop, a lighting sequence is to be controlled by a microcontroller. The output connections are shown below.
When a visitor treads on a pressure mat under the carpet, the lights should flash on and off in sequence three times.
Input
connection
Pin
Output 7
red light 6
yellow light 5
green light 4 3 2 1
pressure mat

48. Pupil Assignment
Develop a PBASIC program that will carry out the instructions shown in the flowchart. Use the following pin configuration.
Input
connection
Pin
Output 7
red light 6
amber light 5
green light 4 3 2 1
start switch

49. Pupil Assignment Input connection Pin Output 7 motor reverse 6
A washing machine operates as follows.
Wait until the start switch is on.
Wait until the door switch is on.
Switch on the LED.
Switch on the solenoid bolt.
Wash cycle: repeated 20 times – motor forwards for five seconds, motor backwards for five seconds.
Spin cycle: repeated 10 times – motor forwards for two seconds, motor backwards for two seconds.
Switch off the solenoid bolt.
Switch off the LED.
Draw a flowchart and write a PBASIC program to control the movement of the washing machine as described above.
Input
connection
Pin
Output 7
motor reverse 6
motor forward 5
solenoid bolt 4
LED 3 2
door
Microswitch 1
start switch

50. Analogue Sensing
Copy the program to your workbooks. Connect a LDR to the input module, key in the program, run and test. In your own words explain what is happening
main: ' make a label called ‘main’
if sensorA > 50 then red ' jump to red if the value > 50
goto green ' value is < 50 so jump to green
red: ' make a label called ‘red’
high 4 ' switch output 4 on
low 5 ' switch output 5 off
goto main ' jump back to start
green: ' make a label called ‘green’
high 5 ' switch output 5 on
low 4 ' switch output 4 off

51. Pupil Assignment
A street lamp must turn on when the light level is below the level ‘100’ and turn off when the level is above ‘100’.
The lamp is connected to output 7 and the LDR light sensor is connected to sensor A.
Draw a flowchart and write a PBASIC program that will make the street lamp work correctly.

52. Pupil Assignment
State whether each of the input transducers below is an analogue or digital sensor.
(a) LDR
(b) reed switch
(c) microswitch
(d) thermistor
(e) variable resistor
(f) tilt switch
(g) push switch
(h) rocker switch
For each of the input transducers give an example of an electronic product that may use that transducer. Explain how the transducer would be used within the product.

53. Number Systems
The Stamp Microcontroller can accept decimal numbers as well as binary numbers. However, we need to tell the microcontroller what we are using.
Decimal values are written as usual: 10 (= 10 in decimal)
Binary values are indicated by a % symbol: %10 (= 2 in decimal)
Your teacher will now show you how to convert decimal to binary and binary to decimal.

54. Pupil Assignment
Convert each of the following binary numbers into decimal. % % % %
Convert each of these decimal numbers into binary. 17 23 11 38 33

55. To do this we use the dirs command.
The “let dirs” command
Up till now, if we wanted to switch on more than one output, we needed to switch them on one by one. However, by using binary, we can now switch on more than one pin at a time.
To enable us to achieve this, we must first tell the microcontroller what pins are outputs and which are inputs.
To do this we use the dirs command.
Let dirs = % ‘let pins 0 to 3 be outputs the rest inputs

56. The “let pins” command
Once we have instructed the microcontroller what is outputs and what is inputs, we use the let pins command.
Let dirs =% ‘all pins outputs
Main:
let pins = % ‘switch on pins 0 to 3
pause ‘1.5 second delay
let pins = 0 ‘switch all pins off
let pins = % ‘switch on pins 4 to 7
let pins = 0 ‘switch off all pins
end ‘end program

57. Stepper Motors
Stepper motors are very accurate motors that are commonly used in computer disc- drives, printers, X–Y plotters and clocks. Unlike d.c. motors, which spin round freely when power is applied, stepper motors require that their power supply is continuously ‘pulsed’ in four different patterns. For each pulse, the stepper motor moves around one ‘step’, typically 7.5 degrees (giving 48 steps in a full revolution).

58. Stepper Motors
The table below shows the four different steps required to make the motor turn. Copy the table into your workbook
Step
Coil 4
(output 7)
Coil 3
(output 6)
Coil 2
(output 5)
Coil 1
(output 4) 1 2 3 4

59. Pupil Assignment
An X-Y plotter movement is controlled by stepper motors. Write a P-Basic program that will rotate the one stepper motor 20 steps in one direction then 20 steps in the opposite direction.
Your teacher will show you how to connect the stepper motor to the stamp.

60. End of unit Assignment
A new automatic railway crossing is to be installed at a local site. The operation of the crossing should follow a set sequence.
Design a PBASIC control program to control the sequence described on the next slide. The train sensors give a logic (1) when the train is sensed. For this simulation, you only need to control one side of the crossing, (one barrier and one warning light).

61. End of unit Assignment
When a train is 1 mile from the crossing, a signal is sent, warning of the train’s approach.
When the warning signal is received, the crossing’s warning lights begin to flash.
The lights should flash on and off continuously at 1 second intervals.
After 30 seconds, the crossing barriers come down.
The barriers remain down until the train activates a second signal 1 mile further down the track.
After 30 seconds the barriers should rise and the lights should stop flashing..