GB2323697A

GB2323697A - Electrical control systems

Info

Publication number: GB2323697A
Application number: GB9706358A
Authority: GB
Inventors: David Smith
Original assignee: Manchester Metropolitan University
Current assignee: Manchester Metropolitan University
Priority date: 1997-03-27
Filing date: 1997-03-27
Publication date: 1998-09-30
Anticipated expiration: 2017-03-27
Also published as: GB9706358D0; GB2323697B

Abstract

This invention relates to an apparatus and a kit for teaching students how to build and program electrical control systems. Building and programming electrical control systems is known to be a difficult task for students particularly in the early stages of tuitition. According to one aspect of the present invention there is provided an apparatus for teaching a student to build and program circuits, which apparatus comprises a support 15 for receiving a microcontroller chip and at least one output device, wherein when received in the support the chip is selectively connectable to the or each device, thereby to enable the chip to control operation of the or each selected output device to which it is connected. The support may be a zero insertion force socket 22. There is also disclosed a kit for building and programming control circuits, the kit including the above apparatus and instructions, such as a computer program, to assist a student with configuring the micro controller.

Description

AN APPARATUS AND A KIT FOR TEACHING STUDENTS HOW TO BUILD AND PROGRAM ELECTRICAL CONTROL SYSTEMS This invention relates to an apparatus and a kit for teaching students how to build and program electrical control systems.

Building and programming electrical control systems is known to be a difficult task for students particularly in the early stages of tuitition. This is because the circuits required are often complex and include many different components which each have to be programmed to interact to provide the desired result. One of the systems which is most commonly used as a teaching exercise is a simple traffic light system. However, even this relatively simple system involves a great deal of circuitry, for example an oscillator circuit, counters and logic decode circuitry, which the student has to assemble and then program.

According to one aspect of the present invention there is provided an apparatus for teaching a student to build and program circuits, which apparatus comprises a support for receiving a microcontroller chip and at least one output device, wherein when received in the support the chip is selectively connectable to the or each device, thereby to enable the chip to control operation of the or each selected output device to which it is connected.

Preferably the support is a zero force insertion socket.

Preferably, the apparatus is such that when the microcontroller is received in the support each of its pins or ports is connected to 4mm socket, thereby to enable the output devices to be selectively connected thereto.

Preferably, each output device is connected to 4mm socket, thereby to enable the pins of the microcontroller to be selectively connected thereto. The output devices may comprise a plurality of LEDs which may be coloured.

The output devices may also comprise a 7 segment display and/or a buzzer and/or an alphanumeric display.

Preferably at least one input device is provided.

Preferably the input devices are able to simulate for example detectors for burglar alarms and/or operational switches and/or output from sensors for counting and/or position or limit sensor outputs on machines with moving parts. The input device may comprise a switch and/or a keypad. In addition an LCD display may be provided with the keypad and used in conjunction with a menu system.

The input device may comprise an analogue to digital converter. The analogue to digital converter may provide information on light level and/or voltage and/or temperature.

Preferably the support, the or each output device and the or each input device are provided on at least one board.

Preferably, the support is provided on a first board, the or each input device is on another board or boards and the or each output device is on yet another board or boards.

Preferably the microcontroller and the output devices, and/or the microcontroller and the input devices are connectable using standard 4mm leads.

According to another aspect of the present invention there is provided an kit for teaching a student how to build and program control circuits, which kit includes the apparatus according to the first aspect of the present invention and additionally instructions to assist the student with configuring the microcontroller.

Preferably the instructions provided comprise a computer program. Preferably the computer program comprises a configuartion section which sets input and output ports of the chip. The computer program may comprise a subroutine section containing at least one program which the student can use when programming the microcontroller chip. The sub-routine may provide a delay routine. The delay routine may be edited by the student, thereby to enable the delay to be varied.

An apparatus and a kit in which the present invention is embodied will now be described by way of example with reference to the following drawings, of which: Figure 1 is a front view of a teaching apparatus; Figure 2 is a circuit diagram of the apparatus of Figure 1; Figure 3 is a circuit diagram of a power supply for the apparatus of Figure 1; Figure 4 is front view of a programmer; Figure 5 is a circuit diagram of a first control circuit; Figure 6 is a circuit diagram of a second control circuit; Figure 7 is a circuit diagram of a third control circuit; Figure 8 is a circuit diagram of a fifth control circuit; Figure 9 is a circuit diagram of a sixth control circuit; Figure 10 is a circuit diagram of a seventh control circuit; Figure 11 is a circuit diagram of a eighth control circuit, and Figure 12 is a circuit diagram of a nineth control circuit.

Figure 1 shows an apparatus having a housing in which housing are supported six boards 15,16,17,18,19,20 arranged in two rows of three 15,17,19 and 16,18,20 respectively. Board 15 is a microcontroller board, boards 16, 17 and 18 are input boards and boards 19 and 20 are output boards.

Microcontroller board 15 is typically provided with a zero insertion force socket 22 for receiving a microcontroller. The socket 22 has a series of individual sockets each of which is adapted to receive a pin of the microcontroller and each of which is connected to a 4mm socket 24. This enables each input port A0, Al, A2, A3 and A4 and each output port BO, B1, B2, B3, B4, B5, B6 and B7 of the microcontroller to be connected to an external device. Included on board 18 is a crystal oscillator 26, typically having an oscillator frequency of 32.768kHz, for providing the necessary clock for the microcontroller, and a pull up resistor for the master clear pin which appears as a RA4, see Figure 2. In addition, the microcontroller board 18 has an on-board voltage regulator 28, see Figure 3, and can be adapted to provide 5 volts to all of the other boards.

The frequency of 32.768kHz is chosen for its practicality in respect of timing events since it easily divides down into whole seconds and readily usable fractions such as 0.5, 0.25 etc. However, it will be understood that any suitable frequency could be used.

The zero force insertion socket 22 is provided to make the fitting of a microcontroller as easy as possible and eliminate problems such as bending pins on insertion.

Typically, the board 18 is designed to receive any of the 18 pin PIC microcontrollers and so can receive virtually the entire PIC 16CX range.

Adjacent the microcontroller board 18 is input board 16 which includes a logic level switch board. This has four basic on-off switches SW1, SW2, SW3 and SW4, each of which is connected to a 4mm socket 30 to enable it to be connected to the microcontroller. These switches SW1, SW2, SW3 and SW4 can be used to simulate many things, for example detectors for burglar alarms or operational switches or outputs from sensors for counting or position or limit sensor outputs on machines with moving parts.

Adjacent input board 16 is input board 17 which has a keypad 32 thereon, typically a matrix keypad 32 having 12 buttons arranged as 3 columns and 4 rows. Each button is connected to a 4mm socket 34. In addition to the keypad 32, input board 17 may be provided with a LCD display.

Board 17 can be used for developing designs that require some kind of data entry, such as personal identification numbers (PIN) or sophisticated burglar alarms or electronic locks such as ignition immobilisers for cars and so on.

Adjacent board 17 and the microcontroller board 15 is input board 18 which includes an analogue to digital converter. The analogue to digital converter may provide information on three types of analogue output, these being light level, voltage and temperature. It will be readily understood by the person skilled in the art that a range of systems can be developed and demonstrated using this board such as automatic night lights with optional programming features, photographic light meters, central heating control systems and battery condition testers.

Adjacent input board 18 is output board 19 which has a 7 segment number display 33 and a buzzer 35. Each segment of the display 33 and the buzzer 35 is connected to a 4mm socket 37. Printed onto the board showing the standard arrangement of 7 segments of a 7 segment display there is graphic. Therefore, not only can the method of coding the digits of a 7 segment display be demonstrated but it can also be usefully included in a project development to achieve designs such as rev counters, simple voltmeters and event/item counters. The buzzer 35 can be used in projects which use an alarm or as a limit warning device.

Adjacent input board 17 and the microcontroller board 15 is output board 20 which includes, typically 8 LEDs 36, each of which is connected to a 4mm socket. The use of 8 LEDS 36 enables each pin of an entire output port of the microcontroller to be viewed. The LEDs 36 can be coloured and arranged so that for example binary counting or a traffic lights system can be demonstrated. The LEDs can be used to simulate many kinds of output, for example indicating the status of a signal line, or when a motor or mains relay is turned on or off, or as indicators in a product design.

When the microcontroller chip is received in the socket 22, each of the devices on the input boards 16, 17 and 18 the output boards 19 and 20 are selectively connectable to its pins via the 4mm sockets using standard 4mm leads. Hence, a student can readily build and experiment with a multitude of different circuits, each circuit being dependant on the output and/or input devices selected.

In use of the apparatus the student typically has to do three things, firstly design a control circuit, secondly program the microcontroller to control that circuit and finally build the circuit including the microcontroller chip. However, in the early stages of tuitition, the circuit design is generally provided so that the student commences with programming the microcontroller chip.

In order to program the chip to control the circuit into which it is to be incorporated various programmers can be used, for example the device shown in Figure 4. This is a PIC 16C84 programmer 40 comprising a zero insertion force IC socket 42, a standard power socket 44, and a standard 36 way IEEE-488 socket 46 which is adapted to accept normal mains cable from a PC. In use the programmer 40 is connected to say a PC and a chip is fitted into the socket 42. The chip is then programmed by typing the necessary program into say a PC and assembling that program into a language which the microcontroller chip can understand, usually using a program provided by the chip manufacturer, and then running the assembled program.

Other programmers can be used, for example the Parallax programmer.

In order to assist the student program the microcontroller, a starter or header program is provided to configure the microcontroller chip and set up some simple subroutines. This program can either be provided on a disc for the student to use or can be provided in an instruction manual and then typed into for example a PC by the student and saved. By providing this header program, the steps which have to be taken by the student are simplified, so that the student can focus on programming the actual control circuit and not become distracted by having to set up the microcontroller itself. A header program suitable for the 16C84 chip is typically as follows (NB this uses the standard instruction set for the 16C84): instruction explanation HEADER84.ASM for 16C84. This sets PORTA as an INPUT (NB 1 means input) and PORTB as an OUTPUT (NB 0 means output). The OPTION register is set to /256 to give timing pulses of 1/32 of a second.

1 second and 0.5 second delays are included in the subroutine section.

"EQUATES" SECTION TMR0 EQU 1 ;means TMR0 is file 1.

STATUS EQU 3 ;means STATUS is file 3.

PORTA EQU 5 ;means PORTA is file 5.

PORTB EQU 6 ;means PORTB is file 6.

ZEROBIT EQU 2 ;means ZEROBIT is bit 2.

COUNT EQU OCH ;a register to count events.

LIST P=16C84 ;we are using the 16C84.

ORG 0 ;the start address in ;memory is 0 GOTO START ;goto start! SUBROUTINE SECTION ;1 second delay.

DELAY1 CLRF TMR0 ; START TMR0 LOOPA MOVF TMR0.W ;READ TMR0 INTO W.

SUBLW .32 ;TIME - 32 BTFSS STATUS.ZEROBIT ;Check TIME-W = 0 GOTO LOOPA ;Time is not = 32.

RETLW 0 ;Time is 32, return.

;0.5 second delay.

DELAYPS CLRF TMR0 ;START TMR0.

LOOPB MOVF TMR0.W ;READ TMR0 INTO W.

SUBLW .16 ;TIME - 16 BTFSS STATUS.ZEROBIT ;Check TIME-W = 0 GOTO LOOPB ;Time is not = 16.

RETLW 0 ;Time is 16, return.

;CONFIGURATION SECTION START BSF STATUS,5 ;Turns to BANK 1.

MOVLW B'00011111' ;5bits of PORTA are I/P TRIS PORTA MOVLW B'00000000' TRIS PORTB ;PORTB is OUTPUT MOVLW B'00000111' ;Prescaler is 1/256 OPTION ;TIMER is 1/32 secs.

BCF STATUS,5 ;Return to BankO.

CLRF PORTA ;Clears PortA.

CLRF PORTB ;Clears PortB.

This program sets up certain parameters and configures the microcontroller so that 5 bits on Port A are inputs, ie A0, Al, A2, A3 and A4 and 8 bits on Port B are outputs that is BO, B1, B2, B3, B4, B5, B6 and B7. In addition the "subroutine section" provides two simple delay routines, DELAY1 which is set up to provide a 1 second delay and DELAYS which is set up to provide a 5 second delay. Each of these can be used by the student and additionally, each can be edited by the student to alter the time delay as appropriate.

Having entered or opened the headed.asm program, the student is then able to concentrate on the more important aspects of how to actually construct and control various circuits.

Figure 5 shows an example of a control circuit which can be used for switching a light on and off repetitively.

In order to make this circuit function, the student has to write a suitable program for the microcontroller. This program commences for example with the program "header.asm" so that the student merely has to add a program specifically for controlling the selected devices in the desired manner, for example: instruction explanation BEGIN BSF PORTB,0 ;Turn ON BO.

CALL DELAYPS ;Wait 0.5 seconds BCF PORTB,0 ;Turn OFF BO.

CALL DELAYPS ;Wait 0.5 seconds GOTO BEGIN ;Repeat END ;YOU MUST END The whole program, that is header.asm plus the control program written by the student, should then be saved, for example as FLASHER.ASM. The next task is to assemble FLASHER.ASM into an object code that the microcontroller understands. This is done by running an assembler program, for example the standard assembler program MPASM. Once the files are assembled, the microcontroller is fitted into the programmer and is programmed.

Having completed the programming the student then has to build the circuit. This involves the student removing the chip from the programmer and fitting it into the zero insertion socket 22 on the microcontroller board 15. The pin B0 of the microcontoller is then connected to one of the LEDs 36 on output board 20. The circuit is then complete and the LED can then be switched on and off under the control of the microcontroller.

Figure 6 is a circuit which can be used to simulate a traffic light system. In this arrangement, the microcontroller output ports B0, B1 and B2 are connected to LEDs G2, A2 and R2 to represent one set of lights and output ports B3, B4 and B5 are connected to LEDs G1, Al and R1 to represent another set of lights. In contrast to the traditional traffic lights circuit, the microcontroller circuit is simple.

In order to program the microcontroller the student again uses the header.asm program. However, in this case in order to increase the time delays the "subroutine section" could be edited to provide say a 2 second delay and a 5 second delay, by for example editing the subroutine section as follows: SUBROUTINE SECTION ;2 second delay.

DELAY2 CLRF TMRO ; START TMRO LOOPA MOVF TMR0.W ;READ TMRO INTO W SUBLW .64 ;TIME - 64 BTFSS STATUS.ZEROBIT ;Check TIME-W = 0 GOTO LOOPA ;Time is not = 64 RETLW 0 ;Time is 64, return ;5 second delay.

DELAYPS CLRF TMR0 ;START TMR0.

LOOPB MOVF TMR0.W ;READ TMRO INTO W.

SUBLW 1.60 ;TIME - 160 BTFSS STATUS.ZEROBIT ;Check TIME-W = 0 GOTO LOOPB ;Time is not = 160 RETLW 0 ;Time is 160, return Having edited header.asm, the student is then able to add a program for controlling the sequence of the lights, for example: instruction explanation ;Program starts now.

BEGIN MOVLW B'00100100' ;R1, R2 on.

MOVWF PORTB CALL DELAY12 ;Wait 2 Seconds.

MOVLW B'00110100' ;R1, Al, R2 on.

MOVWF PORTB CALL DELAY2 ;Wait 2 Seconds.

MOVLW B'00001100' ;G1,R2 on.

MOVWF PORTB CALL DELAY5 ;Wait 5 Seconds.

MOVLW B'00010100' ;A1, R2 on.

MOVWF PORTB CALL DELAY2 ;Wait 2 Seconds.

MOVLW B'00100100' ;R1, R2 on.

MOVWF PORTB CALL DELAY2 ;Wait 2 Seconds.

MOVLW B'00100110' ;R1, R2, A2 on.

MOVWF PORTB CALL DELAY2 ;Wait 2 Seconds.

MOVLW B'00100001' ;R1, G2 on.

MOVWF PORTB CALL DELAYS ;Wait 5 Seconds.

MOVLW B'00100010' ;R1, A2 on.

MOVWF PORTB CALL DELAY2 ;Wait 2 Seconds.

GOTO BEGIN END The program is then saved and assembled as before and the microcontroller chip is fitted into the programmer and is programmed.

Having completed the programming the student then has to build the circuit. This involves the student removing the chip from the programmer 40 and fitting it into the zero insertion socket 22. Ports B0, B1, B2, of the microcontoller are then each connected using 4mm leads to the LEDs G2, A2, R2 respectively on output board 20 and ports B3, B4, B5 are connected to the LEDs G1, Al, R1 respectively also using 4mm leads, so that G1, Al and R1 represent one set of traffic lights and G2, A2 and R2 represent another set. Once connected each set of traffic lights can be switched on and off under the control of the microcontroller.

In this way, because of the use of the header program, the student is able to program the microcontroller to control a set of traffic lights using only three lines of code. In addition, the student is able to alter the delay used to sequence the lights by altering the time delay set in the subroutine section of the header.asm program. This enables the student to experiment with the times delays so that he could alternatively program the chip to control the circuit to operate as say a set of disco lights.

In addition to enabling a student to design control circuits for controlling output devices the apparatus and kit can be used to teach students how to build and program both input and output devices. For example Figure 7 shows a circuit which comprises two input switches SW1 and SW2 on the input board which are connected through the microcontoller to an LED on the output board. This circuit can be used to simulate a switching system in which the LED is turned on when SW1 is switched momentarily from one state to another and the LED is turned off when SW2 is switched momentarily from one state to another.

As before, the student commences with programming the chip. Again the header.asm is used and again the student has to add a program suitable for controlling the circuit, such as: instruction explanation ON BTSC PORTA,0 ;Wait for SW1 to be pressed GOTO ON BSF PORTB,0 ;Turn on LED1.

OFF BTSC PORTA,1 ;Wait for SW2 to be pressed.

GOTO OFF BCF PORTB,0 ;Switch off LED1.

GOTO ON ;Repeat sequence.

END In this case since a time delay subroutine is not required, this could be removed from the header.asm before the whole program, that is header.asm plus the program written by the student, is saved.

As before the program is the converted into assembly language using the assembler, the microcontroller is fitted to the programmer and then programmed. The student then removes the chip from the programmer and fits it into the circuit shown in Figure 7. Once the chip is fitted, the LED can then be switched on or off under the control of the microcontroller chip by activating the switches SW1 and SW2.

Another circuit which relies on the interaction between input and output devices is a scanning circuit, which circuit is operable to monitor the condition of a number of inputs in turn and then execute a section of program if any of them are active. Practical examples of control systems which employ scanning circuits include burglar alarms, in which input sensors are monitored and a siren sounds if an input is active, or keypad scanning circuits in which an LED can be lit or a buzzer can be sounded when a particular key is pressed.

Figure 8 shows a simple scanning circuit in which four switches SWO, SW1, SW2 and SW3 are connected through microcontroller chip to four LEDs, LEDO, LED1, LED2 and LED3. The student can program this circuit so that if a switch is pressed an LED will light and stay on until another switch is pressed.

As before the header.asm program is used and a control program is added by the student. A typical program for controlling this circuit is: instruction explanation ;Program starts now.

SWO BTFSC 2PORTA,0 ;SwitchO pressed? GOTO SW1 ;No.

CLRF PORTB ;Yes, switch off all LEDs.

BSF PORTB,0 Switch on LEDO.

SW1 BTFSC PORTA,1 ;Switchl pressed? GOTO SW2 ;No CLRF PORTB ;Yes, switch off all LEDs.

BSF PORTB,1 ;Switch on LED1.

SW2 BSFSC PORTA,2 ;Swich2 pressed? GOTO SW3 ;No CLRF PORTB ;Yes, switch off all LEDs.

BSF PORTB,2 ;Switch on LED2.

SW3 BTFSC PORTA,3 ;Switch3 pressed? GOTO SWO ;No.

CLRF PORTB ;Yes, switch off all LEDs.

BSF PORTB,3 ;Switch on LED3.

GOTO SWO ;Rescan.

END It should be noted again that the "subroutine" section of header.asm is not required in this case, so that it could be removed before the program is saved.

As before the program is then converted into assembly language using an assembler, the microcontroller is fitted to the programmer and then programmed. The student then fits the programmed chip into the circuit shown in Figure 8 and the LEDs can then be switched on or off under the control of the chip by activating the switches SWO, SW1, SW2 and SW3.

Figure 9 shows another example of a scanning circuit.

In this example the key pad is connected into the microcontroller. Keypads are usually arranged in a matrix format to reduce the number of input and output connections. Typically, a 12 key keypad is arranged in a 3 x 4 format requiring 7 connections. Hence, in this case the input devices are in fact connected to port B, rather than port A as used in the previous examples.

From Figure 9 it can be seen that the column of the keypad containing 1,4,7,and * is connected to BO, the column containing 2,5,8 and 0 is connected to B1, the column containing 3,6,9 and &num; is connected to B2, the row containing 1,2 and 3 is connected to B3, the row containing 4,5 and 6 is connected to B4, the row containing 7,8 and 9 is connected to B5 and the row containing *,0 and # is connected to B6.

The keypad works so that for example when the button 6 is pressed then B2 will be joined to B4 and when key 1 is pressed BO is joined to B3 etc. In order to determine which button has been pressed, the chip should be programmed by the student to set to 0 the port which is connected to one of the columns, and then scan the ports connected to one of the rows to see if one of the buttons in that column has been pressed. If the scan indicates that none of the buttons in that column has been pressed, then the chip moves onto the next column and repeats the scan of the rows. This is repeated until the button pressed is determined.

In this case the header program is slightly different to that employed previously. This is primarily because Port B has to be set up as the input port and Port A has to be set up to be the output port. A typical program is as follows: instruction explanation HEADER84.ASM for 16C84. This sets PORTB as an INPUT (NB 1 means input) and PORTA as an OUTPUT (NB 0 means output). The OPTION register is set to /256 to give timing pulses of 1/32 of a second.

"EQUATES" SECTION STATUS EQU 3 ;means STATUS is file 3.

PORTA EQU 5 ;means PORTA is file 5.

PORTB EQU 6 ;means PORTB is file 6.

LIST P=16C84 ;we are using the 16C84.

ORG 0 ;the start address in ;memory is 0 GOTO START ;goto start ;CONFIGURATION SECTION START BSF STATUS,5 ;Turns to BANK 1.

MOVLW B'00000000' ;PORTA is output TRIS PORTA MOVLW B'11111000' TRIS PORTB ;PORTB is mixed I/O BCF STATUS,5 ;Return to BankO.

CLRF PORTA ;Clears PortA.

CLRF PORTB ;Clears PortB.

The student then has to add to this, a program which enables the microcontroller to work out which button is pressed.

Other circuits which utilise the interaction between input and output devices are shown in Figures 10 to 12.

Figure 10 shows how the 7 segment display 33 on input board 19 is connected to the microcontroller chip. This circuit can be used to count for example how many times the switch SW1 is pressed. Figure 11 shows a more complicated counting circuit. This circuit can be programmed for example to count how many times switch SW1 is pressed and then switch on LED1 when a preselected number of counts is reached. Finally, Figure 12 shows a circuit which uses the analogue to digital converter.

This circuit can be used say as a voltage indicator. As before, for each of these circuits instructions are provided to enable the student to configure the microcontroller chip as required. The student is then able to concentrate on how to control the various devices in the circuits to provide the desired result.

The prgrams described hereinbefore are all directed to the 16C84 microcontroller chip. However, it will be understood that when a different chip is used, and this chip understands a different set of instructions, these programs would have to be adapted to use the appropriate instruction set.

Whilst each of the devices on the input boards 15, 16 and 17 and the output boards 19 and 20 are selectively connectable to the pins of the microcontroller via the 4mm sockets described hereinbefore, it will be understood that additionally or alternatively, the devices could be selectively connected to the microcontroller using selectively operable switches.

The apparatus of the present invention provides a student with considerable scope to experiment with many different circuits.

The kit in which the present invention is embodied enables the student to concentrate on programming the microcontroller chip to control the interaction of the components of the circuit which he has designed without becoming confused or distracted at an early stage of the tuitition by the problems associated with configuring the chip itself.

Claims

CLAIMS:

1. An apparatus for teaching a student to build and program circuits, which apparatus comprises a support for receiving a microcontroller chip and at least one output device wherein, when received in the support, the chip is selectively connectable to the or each device, thereby to enable the chip to control operation of the or each selected output device to which it is connected.

2. Apparatus as claimed in claim 1 wherein the support is a zero insertion force socket.

3. Apparatus as claimed in any preceding claim wherein the apparatus is such that when the microcontroller is received in the support each of its pins or ports is connected to a socket, thereby to enable the output devices to be selectively connected thereto.

4. Apparatus as claimed in claim 3 wherein each output device is connected to a socket, thereby to enable the pins of the microcontroller to be selectively connected thereto.

5. Apparatus is claimed in any preceding claim wherein at least one input device is provided.

6. Apparatus as claimed in claim 5 wherein the support, the or each output device and the or each input device are provided on at least one board.

7. Apparatus as claimed in claim 6 wherein the support is provided on a first board, the or each input device is on another board or boards and the or each output device is on yet another board or boards.

8. A kit for teaching a student how to build and program control circuits, which kit includes apparatus according to any preceding claim and additionally instructions to assist the student with configuring the microcontroller.

9. A kit as claimed in claim 8 wherein the instructions provided comprise a computer program.