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Motor Control Using the SN754410 Quad Half H-Bridge IC

by Al Margolis, founder www.HobbyEngineering.com

An h-bridge is an electrical circuit which allows low power digital circuits, such as microcontrollers, to operate motors and other high energy electrical devices. An h-bridge is essentially a switch. The switch is "flipped" using digital inputs which typically operate at three to five volts and which draw very little current. Just as your little finger can flip a switch that starts a huge motor to lift a drawbridge, an h-bridge allows "little" digital signals to start motors operating at much higher voltages and currents.

Using the SN754410 Quad Half H-Bridge IC

The SN754410 is a quad half h-bridge IC. The "quad" means that it has four circuit elements, so the chip contains four "half h-bridges". A full h-bridge can drive a motor in both directions (clockwise or counterclockwise) by supplying current in either direction through the motor windings. A half h-bridge can supply current flowing in one direction only so the chip can control up to four motors as long as you only need each motor to move in one direction.

The following table is a wiring diagram for the SN754410 when used as two full h-bridges.

Pin	Name	Full H-Brdige Function	Notes
1	1,2EN	Motor 1 Enable	0V (LOW) = disable motor 5V (HIGH) = enable motor You can use this pin to implement an emergency off switch or to activate electrical braking. In most simple robotics application you can just connect this pin to 5V (HIGH / VDD) and save a pin on your microcontroller.
2	1A	Motor 1 Clockwise / Forward	0V (LOW) = ignore 5V (HIGH) = apply current in one direction
3	1Y	Motor 1 Power (Output)
4	Ground	Ground	All 4 ground pins must be connected!
5	Ground	Ground	All 4 ground pins must be connected!
6	2Y	Motor 1 Power (Output)
7	2A	Motor 1 Counterclockwise / Reverse	0V (LOW) = ignore 5V (HIGH) = apply current in the other direction
8	VCC2	Motor Power Source (Input)	This should generally be attached directly to your battery or other primary source. You should not power your motors through your controller board power regulator unless you are absolutley sure that it has adequate current capacity and noise filtering.
9	3,4EN	Motor 2 Enable	0V (LOW) = disable motor 5V (HIGH) = enable motor You can use this pin to implement an emergency off switch or to activate electrical braking. In most simple robotics application you can just connect this pin to 5V (HIGH / VDD) and save a pin on your microcontroller.
10	3A	Motor 2 Clockwise / Forward	0V (LOW) = ignore 5V (HIGH) = apply current in one direction
11	3Y	Motor 2 Power (Output)
12	Ground	Ground	All 4 ground pins must be connected!
13	Ground	Ground	All 4 ground pins must be connected!
14	4Y	Motor 2 Power (Output)
15	4A	Motor 2 Counterclockwise / Reverse	0V (LOW) = ignore 5V (HIGH) = apply current in the other direction
16	VCC1	IC Logic Power (Input)	Regulated 5v (VCC / VDD)

Basic Stamp Example Program

' {$STAMP BS2sx}

' SN754410 Demo Program #1

' This program exercises motors attached to a SN755410NE H-Bridge IC.

' It simply runs the motors full speed in one direction for a period of time,

' pauses and repeats in the opposite direction.

' This program assumes the simplist possible hardware implimentation so three

' Basic Stamp I/O pins are required for each motor.

' The support routines assume that the three connections for each motor are

' made sequentiantially along one side of an APPMOD connector.  That results in

' the numeric sequence of the pins being a sequentional count by two.  The first

' Basic Stamp pin number is the Motor ID and is connected to the enable pin

' for that motor on the h-bridge.  The next Basic Stamp pin (Motor ID + 2)

' is connected to the h-bridge "on" pin for the forward direction.  The last

' pin is connected to the h-bridge "on" pin for the reverse direction.

MotorID VAR Byte        ' Current Motor ID

Motor1  CON 1           ' Motor 1 control on stamp pins 1, 3 and 5

                        ' SN754410 pins 1 (1,2EN), 2 (1A) and 7 (2A)

Motor2  CON 2           ' Motor 2 control on stamp pins 2, 4 and 6

                        ' SN754410 pins 9 (3,4EN), 10 (3A) and 15 (4A)

Loop:

  DEBUG CR, "s"

  MotorID = Motor1

  GOSUB MotorBrake

  MotorID = Motor2

  GOSUB MotorBrake

  PAUSE 1000

  DEBUG "F"

  MotorID = Motor1

  GOSUB MotorForward

  MotorID = Motor2

  GOSUB MotorForward

  PAUSE 1000

  DEBUG "s"

  MotorID = Motor1

  GOSUB MotorBrake

  MotorID = Motor2

  GOSUB MotorBrake

  PAUSE 1000

  DEBUG "R"

  MotorID = Motor1

  GOSUB MotorReverse

  MotorID = Motor2

  GOSUB MotorReverse

  PAUSE 1000

  GOTO Loop

MotorCoast:

  LOW MotorID

  HIGH MotorID + 2

  HIGH MotorID + 4

  RETURN

MotorBrake:

  LOW MotorID + 2

  LOW MotorID + 4

  HIGH MotorID

  RETURN

MotorForward:

  LOW MotorID + 4

  HIGH MotorID + 2

  HIGH MotorID

  RETURN

MotorReverse:

  LOW MotorID + 2

  HIGH MotorID + 4

  HIGH MotorID

  RETURN

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The content on this page was updated on 10/13/2011