Pololu Dual G2 High-Power Motor Driver for
Raspberry Pi
24v14
/POLOLU 3752
18v18
/POLOLU 3750
18v22
/POLOLU 3754
This add-on board makes it easy to control two high-
power DC motors with a Raspberry Pi.
Its twin discrete MOSFET H-bridges support a wide operating voltage range and are
efficient enough to deliver a continuous current without a heat sink. The drivers offer
basic current limiting functionality, and they accept ultrasonic PWM frequencies for
quieter operation. The default pin mappings make it easy to get started, but they can be
customized for more specialized applications.
These G2 dual high-power motor drivers are add-on boards for the Raspberry Pi,
featuring pairs of discrete MOSFET H-bridges designed to drive two large brushed DC
motors. They are designed to mount on and plug into compatible Raspberry Pi boards
(Model B+ or newer), including the Pi 3 Model B and Model A+. Three versions are
available so you can pick the one with the appropriate operating voltage range and
output current capabilities for your project:
DUAL G2 HIGH-
POWER MOTOR
DRIVER 18V22 FOR
RASPBERRY PI
ABSOLUTE
MAX
INPUT
VOLTAGE:
MAX NOMINAL
BATTERY
VOLTAGE:
MAX
CONTINUOUS
CURRENT PER
CHANNEL:
DEFAULT
ACTIVE
CURRENT-
LIMITING
THRESHOLD:
DUAL G2 HIGH-
POWER MOTOR
DRIVER 18V18 FOR
RASPBERRY PI
DUAL G2 HIGH-
POWER MOTOR
DRIVER 24V14 FOR
RASPBERRY PI
30 V
36 V*
18 V
28 V
22 A
18 A
14 A
60 A
50 A
40 A
* 40 V if regulator is disconnected
The minimum operating voltage for all four versions is 6.5 V, while the maximum
operating voltages are given in the above table. The board also includes an integrated
5 V, 2.5 A switching step-down regulator that can be used to power the Raspberry Pi it
is plugged into, enabling operation from a single power supply.
The driver’s default configuration uses six GPIO pins to control the motor drivers,
making use of the Raspberry Pi’s hardware PWM outputs, and it uses two additional
pins to read status outputs from the drivers. However, the pin mappings can be
customized if the defaults are not convenient, and pins for current sensing and limiting
are accessible on the board for more advanced applications.
Note that this motor driver add-on is designed specifically for newer versions of the
Raspberry Pi with 40-pin GPIO headers, including
the
Model B+, Model A+, Raspberry Pi 2 Model B,
and
Raspberry Pi 3 Model B.
The
board matches the Raspberry Pi HAT (Hardware Attached on Top) mechanical
specification, although it does not conform to the full HAT specifications due to the lack
of an ID EEPROM. (A footprint for adding your own EEPROM is available for
applications where one would be useful; pull-ups on SDA, SCL, and WP are provided.)
It is
not
practical to use this expansion board with the original Raspberry Pi Model A or
Model B due to differences in their pinout and form factor.
Features common to all versions
•
•
•
•
•
•
•
•
•
PWM operation up to 100 kHz
Motor indicator LEDs show what the outputs are doing even when no motor is connected
Integrated 5 V, 2.5 A switching step-down voltage regulator powers the Raspberry Pi base for
single-supply operation
Python library
makes it easy to get started using this board as a motor driver expansion board
GPIO pin mappings can be customized if the default mappings are not convenient
Current sensing and limiting pins are exposed for advanced use
Reverse-voltage protection
Undervoltage shutdown
Short circuit protection
The following through-hole connectors and mounting hardware are included with the
board, which ships with its surface-mount components populated:
•
•
•
one 2×20-pin 0.1″ female header
three 2-pin 5 mm terminal blocks
four M2.5 standoffs (11 mm length), screws, and nuts
The 2×20-pin 0.1″ female header should be mounted to the bottom of the board (the
side opposite the surface-mount components). Once soldered, this header is used to
connect the board to the Raspberry Pi’s 40-pin GPIO header. Alternatively, if you want
to continue to have access to the Raspberry Pi’s 40 GPIO pins while the motor driver
board is plugged in, you can install a stackable 2×20-pin female header (not included)
instead.
You can solder the terminal blocks to the six large through-holes to make your motor
and motor power connections, or you can solder a 0.1″ male header strip (not included)
into the smaller through-holes that border these larger holes. Note, however, that the
terminal blocks are only rated for 16 A, and each header pin pair is only rated for a
combined 6 A, so for higher-power applications, thick wires should be soldered directly
to the board.
The motor driver includes six 100 μF or 150 μF electrolytic power capacitors, and there
is room to add additional capacitors (e.g. to compensate for long power wires or
increase stability of the power supply). Additional power capacitors are usually not
necessary, and no additional capacitors are included with this motor driver.
Using the motor driver board
Power
An appropriate motor power supply should be connected to the motor driver’s large VIN
and GND pads. The board includes a reverse-voltage protection circuit that helps
prevent damage in case the motor power supply is connected backward. The reverse-
protected input voltage can be accessed for use in other circuits through the two pins
labeled VM on the left side of the board.
By default, the motor power supply also feeds a 5 V, 2.5 A switching step-down
regulator that provides power to the connected Raspberry Pi. An ideal diode circuit
makes it safe to have a different power supply connected to the Raspberry Pi through
its USB Micro-B receptacle while the motor driver is connected and powered.
If you want to power the Raspberry Pi separately, the regulator can be disconnected by
cutting two exposed traces on the board: one between the surface-mount pads labeled
“VM” and “REG IN”, and another between the two pins by the “REG OUT” label, as
shown to the right. On the 24v14 and 24v18 versions, disconnecting the regulator
increases the absolute maximum operating voltage of the board to 40 V.
Default pin mappings
This table shows how the Raspberry Pi’s GPIO pins are used to interface with the motor
drivers:
RPI
GPIO
PIN
5
6
12
MOTOR DRIVER PIN
DESCRIPTION
Motor 1 FLT
Motor 2 FLT
Motor 1 PWM
Fault indicator: When the driver channel is functioning
normally, this pin should be pulled high by the Raspberry
Pi. In the event of a driver fault, FLT is driven low. See
below for details.
Motor speed input: A PWM (pulse-width modulation)
signal on this pin corresponds to a PWM output on the
corresponding channel’s motor outputs. When this pin is
low, the motor brakes low. When it is high, the motor is on.
The maximum allowed PWM frequency is 100 kHz.
Inverted sleep input: This pin is pulled low by default,
putting the motor driver channel into a low-current sleep
mode and disabling the motor outputs (setting them to
high impedance). SLPmust be driven high to enable the
motor channel.
Motor direction input: When DIR is low, motor current
flows from output A to output B; when DIR is high, current
flows from B to A.
13
Motor 2 PWM
22
Motor 1 SLP
23
Motor 2 SLP
24
25
Motor 1 DIR
Motor 2 DIR
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