The board uses GPIO pins 5, 6, 12, and 13 to control the motor driver, making use of the Raspberry Pi’s hardware PWM outputs, although the pin mappings can be customized if the defaults are not convenient. Note that it 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; 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.

We also have a similar DRV8835 shield for Arduinos and Arduino-compatible boards and a smaller DRV8835 carrier for those using a different controller or with tighter space constraints. For a more powerful motor driver, consider the dual MC33926 motor driver for Raspberry Pi.

Although the DRV8835 itself works with a minimum motor supply voltage of 0 V, this board’s reverse-protection circuit limits the minimum to 1.5 V. If a lower motor supply voltage is required, please consider using our DRV8835 carrier with motor power supplied through the VMM pin.

Features

• Dual-H-bridge motor driver: can drive two DC motors or one bipolar stepper motor
• Motor supply voltage: 1.5 V to 11 V
• Logic supply voltage 2 V to 7 V
• Output current: 1.2 A continuous (1.5 A peak) per motor
• Motor outputs can be paralleled to deliver 2.4 A continuous (3 A peak) to a single motor
• PWM operation up to 250 kHz (ultrasonic frequencies allow for quieter motor operation)
• Two possible interface modes: PHASE/ENABLE (default – one pin for direction, another for speed) or IN/IN (outputs mostly mirror inputs)
• Board can optionally power the Raspberry Pi base directly through add-on regulator (not included)
• 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
• Reverse-voltage protection on motor power supply
• Under-voltage lockout and protection against over-current and over-temperature

Assembly with included hardware

Before the motor driver board can be plugged into your Raspberry Pi, female headers must be soldered into the appropriate holes. The kit ships with a 2×17-pin 0.1″ female header that should be mounted to the bottom of the board (the side with surface-mount components). Once the kit is assembled, it should be plugged into the leftmost position on the Raspberry Pi’s 40-pin GPIO header, leaving six pins exposed on the right, as shown in the picture below.

Three 2-pin, 5 mm terminal blocks are included for making easy motor and power connections to the board once they have been slid together and soldered to the six large through-holes. Alternatively, you can solder 0.1″ male header pins to the smaller through-holes above the terminal block holes, or you can just solder wires directly to the board.

Shorting blocks and 0.1″ male headers (not included) can be used to make some of the more advanced optional modifications to the board, such as remapping the control pins or paralleling the outputs.

A Raspberry Pi is not included.

Using the motor driver

In the board’s default state, the motor driver and Raspberry Pi are powered separately, though they share a common ground and the DRV8835 receives its logic supply voltage (VCC) from one of the Raspberry Pi’s 3V3 power pins. When used this way, the Raspberry Pi must be powered via its USB Micro-B receptacle, and the motor driver board must be supplied with 1.5 V to 11 V through its large VIN and GND pads. However, the motor driver board provides a set of three through-holes where you can conveniently connect an appropriate voltage regulator, allowing the motor supply to also power the Raspberry Pi (see the Powering the Raspberry Pi from the motor driver board section below).

By default, the driver is configured to operate in PHASE/ENABLE mode, in which a PWM signal applied to the ENABLE pin determines motor speed and the digital state of the PHASE pin determines direction of motor rotation. GPIO 12 and 5 are used to control the speed and direction, respectively, of motor 1, and GPIO 13 and 6 control the speed and direction of motor 2. The table below shows how the inputs affect the outputs in this mode:

PHASE/ENABLE mode should be suitable for most applications.

Configuring the board for IN/IN mode

The operating mode of the driver is controlled by the MODE pin, which the board pulls high to VCC through a 20 kΩ resistor to select PHASE/ENABLE mode by default. The pin labeled “MODE” can be driven low (or connected directly to ground) to switch the control interface to IN/IN, which allows for slightly more advanced control options as described in the table below:

When adding a voltage regulator to the motor driver board, take care to orient it correctly: note that the motor driver board’s VOUT pin should connect to the regulator’sVIN pin, while the regulator’s VOUT pin should connect to the motor driver board’s 5V pin.

There are several considerations to keep in mind when powering the Raspberry Pi through a voltage regulator in this way:

• You must never connect a different power supply to the Raspberry Pi (including through its USB Micro-B receptacle) while the regulator is connected, as doing so will create a short between the voltage regulator’s output and the external power supply that could permanently damage the Raspberry Pi, the regulator, and/or the power supply.

• Your motor power supply must be an acceptable voltage for both your regulator and the DRV8835.

• The regulator should be able to handle the power requirements of the Raspberry Pi. The Raspberry Pi typically uses a few hundred milliamps at 5 V (depending on the specific model), although its current draw can exceed 1 A if it is also supplying power to USB devices and other peripherals. While linear regulators like a 7805 might fit in the regulator mounting location, they could generate excessive heat or shut down at higher input voltages and output currents. We recommend using a switching regulator (like our S7V7F5, as mentioned above).

Real-world power dissipation considerations

The DRV8835 datasheet recommends a maximum continuous current of 1.5 A per motor channel. However, the chip by itself will overheat at lower currents. For example, in our tests at room temperature with no forced air flow, the chip was able to deliver 1.5 A per channel for approximately 15 seconds before the chip’s thermal protection kicked in and disabled the motor outputs, while a continuous current of 1.2 A per channel was sustainable for many minutes without triggering a thermal shutdown. The actual current you can deliver will depend on how well you can keep the motor driver cool. Our tests were conducted at 100% duty cycle; PWMing the motor will introduce additional heating proportional to the frequency.

This product can get hot enough to burn you long before the chip overheats. Take care when handling this product and other components connected to it.

Schematic diagram

Dimensions

General specifications

Notes:

1

Without included hardware.

2

The DRV8835 itself has a minimum motor supply voltage of 0 V, but the board's reverse-voltage protection circuit limits the minimum to 1.5 V.

3

Typical results with 100% duty cycle at room temperature.

File downloads

Pololu DRV8835 Dual Motor Driver Kit for Raspberry Pi schematic (215k pdf)

Printable schematic for the Pololu DRV8835 Dual Motor Driver Kit for Raspberry Pi.

Texas Instruments DRV8835 motor driver datasheet (1MB pdf)

Recommended links

Python library for the Pololu DRV8835 Dual Motor Driver Kit for Raspberry Pi

This Python library for the Raspberry Pi makes it easy to interface with Pololu’s DRV8835 dual motor driver kit and use it to drive a pair of brushed DC motors. An example program is included with the library.

Texas Instruments DRV8835 product page

Texas Instruments product page for the DRV8835, where you can find the latest datasheet and additional resources.