ARM HOW-TO GUIDE Interfacing Relay with LPC2148 … · 12/23/2014 · Pin Assignment with LPC2148 RELAY SPDT LPC2148 Lines RELAY Power Select s ... The Interfacing Relay with LPC2148

ARM HOW-TO GUIDE

Interfacing Relay with

LPC2148 ARM

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Contents at a Glance

ARM7 LPC2148 Primer Board ........................................... 3

Relay ............................................................................... 3

Interfacing Relays ............................................................ 4

Interfacing Relay with LPC2148 ........................................ 5

Pin Assignment with LPC2148 .......................................... 5

Circuit Diagram to Interface Relay with LPC2148 .............. 6

Source Code .................................................................... 6

C Program to control Relay in LPC2148 ............................. 7

Testing the LED with LPC2148 .......................................... 8

General Information ........................................................ 9



ARM7 LPC2148 Primer Board

The ARM7 LPC2148 Primer board is specifically

designed to help students to master the required skills in

the area of embedded systems. The kit is designed in such

way that all the possible features of the microcontroller will

be easily used by the students. The kit supports in system

programming (ISP) which is done through serial port.

NXP’s ARM7 (LPC2148), ARM Primer Kit is proposed to

smooth the progress of developing and debugging of

various designs encompassing of High speed 32-bit

Microcontrollers.

Relay

Relays are devices which allow low power circuits to

switch a relatively high Current/Voltage ON/OFF. A relay

circuit is typically a smaller switch or device which drives

(opens/closes) an electric switch that is capable of carrying

much larger current amounts.



Interfacing Relays

Fig. 1 shows how to interface the Relay to

microcontroller. There are 2 input channels. Each input is

connected to the triggering coil of the respective relay.

There are 2 output channels that each correspond to an

input. When the input is energized, the relay turns on and

the '+' output is connected to +12v. When the relay is off,

the '+' output is connected to Ground. The '-' output is

permanently wired to Ground.

Fig. 1 Interfacing Buzzer to Microcontroller



Interfacing Relay with LPC2148

We now want to control the relay operations by using

LPC2148 Primer Board. Here we are using two Relays. The

relay consists of a coil and a switch. When the coil is

energized, the switch closes, connecting the two contacts

together. ULN2803 is used as a driver for port I/O lines,

drivers output connected to relay modules. Connector

provided for external power supply if needed.

Relay Module : Port P1 pins (Realy1 – P1.20) and

Relay2-P1.21) for relay module, make port pins to high,

relay will activated.

Pin Assignment with LPC2148

RELAY SPDT LPC2148 Lines RELAY Power Select

REL

AY

Mo

du

les Relay-1 P1.20

JP8

- Internal +5V (Stepper Motor)

Relay-2 P1.21

Note : Relay selection make switch SW28 to SM/RL label marking position

+5V

ONOFF

SW28

PWR ON/OFF

1234

8765

7SEGLCDSM/RLGLCD

2 3 1



Circuit Diagram to Interface Relay with LPC2148

Source Code

The Interfacing Relay with LPC2148 program is very

simple and straight forward, which control the relays in

LPC2148 Primer Board. The relay is working that uses a

delay procedure loop based software delay. The C programs

are developed in Keil software.

STM_A

U4

ULN2803A

I11

I22

I33

I44

I55

I66

I77

I88

GND9

O118

O217

O316

O415

O514

O613

O712

O811

COMM10

STM_B

STM_DSTM_C

RL2RL1

C32

22pf

C33

22pf

X11

12MHz

3.3V

LPC2148

U16

VSS16 V

DD

A7

VSS218

VD

D3

23

VSS325

VD

D2

43

VSS442

VR

EF

63

XT

AL1

62

XT

AL2

61

VSSA59

VD

D1

51

VSS550

P1.1616

P1.1712

P1.188

P1.194

P1.2048

P1.2144

RELAY SPDT

R1_CR1_NO

JP9

RELAY O/P1

112233

R1_NC R2_NO

JP10

RELAY O/P2

112233

R2_NCR2_C

LS3

RELAY SPDT

35

412

67

8

R2_NC

R2_NO

ULN_PWR

R26

330E

RL2

D5

LED

12

R2_C

RL2

ULN_PWR

R1_NO

JP11

RELAY O/P1

112233

R1_NCR1_C

LS2

RELAY SPDT

35

412

67

8

R1_NCR1_C

R25

330E

RL1

D4

LED

12

ULN_PWR

R1_NO

RL1



C Program to control Relay in LPC2148 ***************************************************************************************

Title : Program to control Relay ***************************************************************************************

#include <LPC214x.h>

#include <stdio.h>

#define RLY1 20 //RLY1 (P1.20)

#define RLY2 21 //RLY2 (P1.21)

void main(void)

{

PINSEL2 = 0x00;

IODIR1 = 1 << RLY1; //Configure P1.20 Output

IODIR1 |= 1 << RLY2; //Configure P1.21 Output

while(1) //loop forever

{

IOSET1 = 1 << RLY1;

Delay();

IOCLR1 = 1 << RLY1;

Delay();

IOSET1 = 1 << RLY2;

Delay();

IOCLR1 = 1 << RLY2;

Delay();

}

}

void Delay()

{

unsigned int i,j;

for(i=0;i<2000;i++) for(j=0;j<900;j++);

}



To compile the above C code you need the KEIL

software. They must be properly set up and a project with

correct settings must be created in order to compile the

code. To compile the above code, the C file must be added

to the project.

In Keil, you want to develop or debug the project

without any hardware setup. You must compile the code for

generating HEX file. In debugging Mode, you want to check

the port output without LPC2148 Primer Board.

The Flash Magic software is used to download the hex

file into your microcontroller IC LPC2148 through UART0.

Testing the LED with LPC2148

Give +3.3V power supply to LPC2148 Primer Board; the

Relay module is connected with LPC2148 Primer Board.

When the program is downloading into LPC2148 in Primer

Board, the Relay output is working that the Relay is ON



some time period and the Relay is OFF some other time of

period.

If you are not getting any output from Relay, then you

just check the jumper connections & check the Relay is

connected properly. Otherwise you just check it with

debugging mode in Keil. If you want to see more details

about debugging just see the videos in below link.

How to Create & Debug a Project in Keil.

General Information

For proper working use the components of exact values

as shown in Circuit file. Wherever possible use new

components.

Solder everything in a clean way. A major problem

arises due to improper soldering, solder jumps and

loose joints.

Use the exact value crystal shown in schematic.

More instructions are available in following articles,

http://youtu.be/EzOCple4POk



User Manual of LPC2148 Primer Board.

Tutorial of how to create & Debug a project in Keil.

http://www.pantechsolutions.net/index.php?option=com_k2&view=item&layout=item&id=686&virtuemart_category_id=1&Itemid=19

http://www.pantechsolutions.net/index.php?option=com_k2&view=item&layout=item&id=313&virtuemart_category_id=1&Itemid=19



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ARM HOW-TO GUIDE Interfacing Relay with LPC2148 … · 12/23/2014 · Pin Assignment with LPC2148 RELAY SPDT LPC2148 Lines RELAY Power Select s ... The Interfacing Relay with LPC2148

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