Digilent 410-259P User Manual

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DIR1

EN1 Result

DIR2 EN2 Result

Revision: February 4, 2013
Note: This document applies to REV A of the board.

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Overview

The PmodDHB1 uses the Texas Instruments
DRV8833 dual H-Bridge motor driver chip to
drive two DC motors or one stepper motor.

Features include:

• Motor voltage can be driven up to

11.8V, with a recommended 10.8V
maximum

• Two H-Bridge interfaces capable of

1.5A RMS (2A Peak)

• 2-channel quadrature encoder
channels for Hall-effect sensors

• Two JST 6-pin connectors for direct
connection to Digilent motor-gearboxes

• Logic input voltage range of 2.5V to 5V

Functional Description

For a detailed description of the Texas
Instruments DRV8833 please refer to the
device data sheet available at TI.com.

The DHB1 is controlled through the Pmod
connector J1. Logical levels on ENx and DIRx
determine the Motor Direction and speed of the
attached motors. The DHB1 uses a
demultiplexer and pull-down resistors on the
inputs to the DRV8833 H-Bridge pins to ensure
that the H-Bridge works in fast decay mode.

The intended operation of the DHB1 uses the
enable pin as the PWM input and the direction
pin as a logic level selector to set the direction
of the motor rotation. Table 1 lists the motor
responses that result from various input
combinations.

The DRV8833 chip provides overcurrent
protection on the motor drive circuits. Each
internal drive FET is independently monitored
for an overcurrent condition and will be shut
down internally to protect the chip. When an

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overcurrent condition is sensed the chip will
shut down the FET with the fault and then set
the NFAULT pin low signaling a fault condition
on the chip. The remaining FETs will continue
to operate as normal. When the fault condition
is over, the chip will self-reset and return the
NFAULT logic level to logic high. (See Table 2
for connector descriptions.)

There are two Schmitt trigger buffered inputs
on connectors J2, J3, J7 and J8 that bring
motor speed feedback signals to the controlling
system board. The Digilent motor and gearbox
have hall-effect sensors arranged in a
quadrature encoder format. These buffers
have 5V tolerant inputs, when operated at

3.3V.

0 0 Stop
0 1/PWM Forward
1 0 Stop
1 1/PWM Reverse

0 0 Stop
0 1/PWM Forward
1 0 Stop
1 1/PWM Reverse

Table 1: Motor Control

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PmodDHB1™ Reference Manual

Jumper

Setting

Description

Connector J1

– H-Bridge Interf

aces

Pin Signal

Description

Connector J2

- M1 JST 6

-

Pin Motor Connector

Connector J3

- M1 JST 6

-

Pin Motor Connector

Connector J4

- VM

Connector J5

- M1 Power

Connector J6

- M2 Power

Connector J7

- M1 Feedback

Connector J8

- M2 Feedback

Connector J9

- Fault

Connector J10

- Sleep

The quadrature encoder signals are a pair of
square waves whose frequency is proportional
to motor rotation speed and with the pulses 90°
out of phase. You can determine the motor
speed with the frequency and motor rotation
direction by the phase relationship between the

1 EN1 Motor 1 Enable
2 DIR1 Motor 1 Direction
3 S1A Motor 1 Sensor A Feedback
4 S1B Motor 1 Sensor B Feedback
5 GND Power Supply Ground
6 VCC Power Supply (3.3V)
7 EN2 Motor 2 Enable
8 DIR2 Motor 2 Direction
9 S2A Motor 2 Sensor A Feedback
10 S2B Motor 2 Sensor B Feedback
11 GND Power Supply Ground
12 VCC Power Supply (3.3V)

1 VM Motor Power
2 GND Power Supply Ground

1 M1+ Motor 1 Positive Supply
2 M1- Motor 1 Negative Supply

1 M2+ Motor 2 Positive Supply
2 M2- Motor 2 Negative Supply

1 SA1-IN Sensor A From Motor 1
2 SB1-IN Sensor B From Motor 1
3 GND Power Supply Ground
4 VCC Power Supply (3.3V)

1 SA2-IN Sensor A From Motor 2
2 SB2-IN Sensor B From Motor 2
3 GND Power Supply Ground
4 VCC Power Supply (3.3V)

1 NFAULT Overcurrent Condition
2 GND Power Supply Ground

1 NSLEEP Puts device into sleep state
2 GND Power Supply Ground

Table 2: Connector Descriptions

®

two signals.

www.digilentinc.com

Jumper Settings

Jumpers JP1 and JP2 allow both h-bridge
outputs to be run from the same enable and
direction pins. This allows the two bridge
outputs to be operated in parallel to drive a
single motor with twice the current. Refer to
Table 3 for available settings.

JP1

JP2

Pulse Width Modulation and Motor
Speed Control

Operators can control motor speed by varying
the input voltage to a circuit. However, you
can only apply a logic high or logic low signal
to the motor in a digital circuit. There are only
two ways to control a dc motor digitally. Either
use a variable resistance circuit to control the
motor voltage, or pulse the power to the motor.
Since variable resistance circuitry is expensive,
complicated, and energy inefficient because of
heat loss, Digilent recommends controlling
motor speed through pulse width modulation
(PWM).

Pulse width modulation is a digital method of
transmitting an analog signal. Even though
PWM is not a clean source of DC output
voltage, it controls motors well.

Figures 1 through 3 illustrate a PWM system
with an input frequency of 2KHz. You control
the motor speed by adjusting the time each
wave remains at peak output power. Figure 1
demonstrates a 10% “duty cycle,” where the
signal is logic high for only 1/10 of a
wavelength. This 10% positive peak is equal to
10% of the total 3.3V input, or 0.33V. (See

1 Motor 2 Uses EN1
3 Motor 2 Uses EN2
1 Motor 2 Uses DIR1
3 Motor 2 Uses DIR2

Table 3: Set Jumper Description

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