Microcontrollers cannot drive motor and relays because of its high current requirements. In order to drive them, we need special current drivers and Motor relay board comes into the picture because of these requirements.

The Motor Relay Board drives motors and relays by supplying sufficient current. It can drive one Relay and four DC Motor or one stepper motor at a time.

Motor Relay Board

Introduction

The Motor relay board eases the task of interfacing external motor and AC devices with the PIC Microcontroller. It has ULN2003 drivers for high current applications like Motor driving and Relay driving circuits for AC device interfacing.

Sections

Relay driver

Using the provided relay circuit, 230V devices can be controlled. This section is helpful for automating the ON and OFF.

Motor Driver

The DC motor can be controlled using this section, there is 4 ULN2003 driver controlled lines for driving motors and each provides sufficient current to control the DC motor.

External Interfaces

Terminal block (3pin) – For connecting Relay IN and OUT
Terminal Block(7pin) – For connecting 4 lines of Motor, 1 for power and 2 Ground

Connecting the Board

Power up the board using SW1, power LED will glow
Connect the Port connector to the default port
Shunt the Jumpers in J4
Use jumper caps to select port pins. First four pins (0, 1, 2&3) are Relay selector. The relay can connect to 4 pins.
Use port pins 4,5,6&7 for Motors in the order of Motor D, C, B&A
Set the input port pin correspondingly to turn ON/OFF the Relay/Motor.

Operation

There is an alternate header, J3 for accessing individual pins.

J3	1	2	3	4	5	6	7	8
Pin Name	Port 0	Port 1	Port 2	Port 3	Port 4	Port 5	Port 6	Port 7

The Jumper description is as below, J4.

J4	1	2	3	4	5	6	7	8
Pin Name	Relay	Relay	Relay	Relay	Motor A	Motor B	Motor C	Motor D

The Relay and Motor inputs can be directly accessed by the header J5.

J5	1	2	3	4	5	6	7	8
Pin Name	Relay	Relay	Relay	Relay	Motor A	Motor B	Motor C	Motor D

Terminal blocks

Terminal blocks are used for connecting Motor, external supply and relay controlled equipment. There are three terminal blocks. One is for Motor which is a 7 pin, another one a 2 pin for connecting external 12V supply and 3-pin terminal block is used for connecting relay inputs and outputs.

Pin arrangements in terminal blocks are as below.

Relay block

J1	1	2	3
Pin Name	NC	COM	NO

NC – Normally Closed

COM – Common

NO – Normally open

Motor block

J8	1	2	3	4	5	6	7
Pin Name	VCC	Motor 1	Motor 2	Motor 3	Motor 4	GND	GND

VCC – Supply from External 12V or internal 9V whichever is higher

External supply block

J6	1	2
Pin Name	12V	GND

12V – External power for motor

GND – Ground

Power Headers

There are two power headers available in this board, J9 for 9V and J7 for 5V.

J7	1	2	3	4
Pin Name	5V	5V	GND	GND

J9	1	2	3	4
Pin Name	9V	9V	GND	GND

Motor Operation

There are 4 lines for motor control and both DC motor and stepper motor can be interfaced to the board. The motor can be interfaced to a terminal block, J8. The pins 2, 3, 4 and 5 are for motor lines.

Stepper Motor

For a Unipolar stepper motor, connect 4 lines to the motor terminals and a common terminal to the VCC. Put the jumper cap over 5, 6, 7 and 8 pins of J4 to connect pins to the microcontroller port.

For a Bipolar stepper motor, connect 4 lines to each of the terminals. Put the jumper cap over 5, 6, 7 and 8 pins of J4.

DC Motor

For DC motor, connect the motor line to the any one of the motor terminals and VCC to the common. Connect the jumper cap on the J4 for the corresponding pin.

Relay operation

The relay can be operated using any one of the first 4 port pins. Select the pin using the jumper cap on J4.

The relay has 3 terminals to connect,

NO – Normally open
COM – Common terminal
NC – Normally closed

Connect the input in COM terminal. NO terminal will be connected to the COM terminal during the Relay OFF condition and NC will be connected to the COM terminal during ON condition. The relay can be used to control 230V devices.