axe020

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revolution

28-P28-P28-P28-P28-PINININININ PPPPPRRRRROJECTOJECTOJECTOJECTOJECT BBBBBOOOOOARDARDARDARDARD

Contents:

AXE020 28-pin Project Board with input/output cables

Introduction

The 28-pin p roject bo ard is designed to allow rapid prototyping with

28-pin PICAXE microcontro llers. The b oard provides connection s for

eight d igital inputs (inp uts portC 0-7), four an alogue inputs (inp uts

portA 0-3) and eight digital outputs (ou tputs portB 0-7). Each of the

outputs is driven through a ULN2803A darlington driver, which will drive up to

800m A per outp ut. Ribbon cables with conn ectors are also included, which enable easy

interfacing to the board. Space is provided on th e board for adding an option al motor

driver IC, thro ugh which DC motors can be con trolled with forward/reverse direction al

control.

Power

The b oard can be po wered by a single, or two separate, power supplies. When two power

supplies are used the second separate supply (V2+) is used to power the output devices.

This is useful when a higher voltage is required ( e.g. when d riving a 12V stepper m oto r) or

when it is necessary to isolate the o utpu ts to avoid no ise problems (e.g. when using radio-

control servos).

The p rimary po wer supply (V1+) for the in terface is a 5V or 4 .5V DC. This is conn ected via

the b attery clip conn ector. DO NOT use a 9V PP3 battery, as the interface does not include

a voltage regulator.

Revolution Education Ltd. Web: www.picaxe.co.uk Version 3.0 04/201028-PINPROJ.P65

these two pins

connected

0V

V2+

When two p ower supp lies

are required the second

supply is con nected to

jumper E as shown right.

When a single power

supply is used a jump er

link is required on the

external power jum per

link E as shown right.

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revolution Revolution Education Ltd. Web: www.picaxe.co.uk Version 3.0 04/2010 AXE020.PMD

228-PIN PROJECT BOARD

Digital Outputs

Each digital outpu t is connected to a darlington transistor as shown below.

ULN2803A

M

MICRO-CONTROLLER

V1+ (5V)

0V

V2+ (5-12V)

0V

1

2

3

4

5

6

7

8

9

18

17

16

15

14

13

12

11

10

both 0V lines must be connected

separate supply

M

MICRO-CONTROLLER

5V

0V

28-Pin Project Board Circuit

On the board the transistors are contained in a single ULN2803A darlington driver IC.

The equivalent output circuit is shown below.

28

27

26

25

24

23

22

21

20

19

18

17

16

15

1

2

3

4

5

6

7

8

9

10

11

12

13

14

4 MHz

4k7

V1+

0V

Optionalresetswitch

ULN2803A

analogue 0

analogue 1

analogue 2

analogue 3

(serial input)

(serial output)

V2+

in 0

in 1

in 2

in 3

in 4

in 5

in 6

in 7

out 7

out 6

out 5

out 4

out 3

out 2

out 1

out 0

all 10k(array)

jumper link addedwhen using singlepower supply (V1+)

0V

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1 0V

2 0V

3 7

4 V2+

5 6

6 V2+

7 5

8 V2+

9 4

10 V2+

11 3

12 V2+

13 2

14 V2+

15 1

16 V2+

17 0

18 V2+

19 V2+

20 V2+

0V

out 7

out 6

out 5

out 4

out 3

out 2

out 1

out 0V2+

digital outputs

The d igital outpu t pins o n the b oard are identified as follows:

The ou tput ribbo n cable conn ector has th e following pin arrangement ( wire 1 is marked

with red ink).

wire 1

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Motor Driver

An option al L293D mo tor driver IC (not supplied) m ay be added to th e basic interface.

This provides forward-backward control of two DC motors, controlled by outputs 4 to 7.

Naturally, if only on e mo tor is to be controlled then only two outp ut lines are used.

Both inputs low - motor halt

First output high, second output low - motor forward

First output low, second output high - m otor reverse

Both inputs high - motor halt

Changing the states of the input pins has the effect of altering the direction of current

flow throu gh the mo tor, as shown below.

Note th at the L293D will become warm with continuo us use. The end user may choo se

to bon d a heatsink onto the top of the chip (to h elp keep it cool) if required.

Motor A and B are connected to the interface via the pads provided beside the L293D

chip position . It is necessary to solder conn ectors or wires into these pad s.

optional L293Dmotor driver IC

0V

V2+

0V 0V

M

Pin 4

L293D

5V

In 1

Out 1

0V

0V

Out 2

In 2

V+

5V

In 3

Out 3

0V

0V

Out 4

In 4

5V

1

8

16

9Pin 5 To V2+

V2+

Motor A M

Pin 6

Pin 7

Motor B

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Digital I nputs

The d igital inpu ts have a 10k

pull down resistor on each

input pin.

The equivalent input circuit is

shown right.

The inp ut ribbon cable conn ector has the following pin arrangement (wire 1 is markedwith red ink).

MICRO-CONTROLLER

input pin

10k

5V

0V

digital inputs

V1+

in 0

in 1

in 2

in 3

in 4

in 5

in 6

in 7

0V

wire 1

20 V1+

19 V1+

18 V1+

17 0

16 V1+

15 1

14 V1+

13 2

12 V1+

11 3

10 V1+

9 4

8 V1+

7 5

6 V1+

5 6

4 V1+

3 7

2 0V

1 0V

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Analogue Input Channels

The an alogue input chan nels are left floating (n o conn ection) .

The equivalent input circuit is shown below.

The an alogue input ribbo n cable connector has the following pin arrangement (wire 1 is

marked with red ink).

MICRO-CONTROLLER

input pin

V1+

0V

analogueinput

analogueinputs

V1+

in 0

in 1

in 2

in 3

0V

Order Codes:

AXE020 28-p in Pro ject Bo ard

AXE0 40 In fra-red Up grad e Pack

AXE02 7 USB Pro gram m in g Cab le

IC03 0 L29 3D 16 -p in Mo to r D river IC ( op tio nal)

10 V1+

9 ADC0

8 V1+

7 ADC1

6 V1+

5 ADC2

4 V1+

3 ADC3

2 0V

1 0V

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