Pololu G2 High-Power Motor Driver 24v30 CS

Overview

The Pololu G2 high-power motor driver is a discrete MOSFET H-bridge designed to drive large brushed DC motors. The H-bridge is made up of one N-channel MOSFET per leg; the rest of the board contains the circuitry to take user inputs and control the MOSFETs. The absolute maximum voltage for this motor driver is 40 V, and higher voltages can permanently destroy the motor driver. Under normal operating conditions, ripple voltage on the supply line can raise the maximum voltage to more than the average or intended voltage, so a safe maximum voltage is approximately 34 V.

Note: Battery voltages can be much higher than nominal voltages when they are charged, so the maximum nominal battery voltage we recommend is 28 V unless appropriate measures are taken to limit the peak voltage.

The versatility of this driver makes it suitable for a large range of currents and voltages, with the ability to deliver up to around 30 A of continuous current without heat sinking or forced airflow. The module offers a simple interface that requires as few as two I/O lines while still allowing for your choice of sign-magnitude or locked-antiphase operation. An on-board current sensor gives a direct measurement of the motor current, and the driver can limit the motor current to a configurable threshold. The power supply inputs feature reverse-voltage protection, while integrated detection of various fault conditions helps protect against other common causes of catastrophic failure; however, please note that the board does not include over-temperature protection.

Features and specifications

• H-bridge motor driver: can drive one bidirectional brushed DC motor
• Operating voltage: 6.5 V to 40 V (absolute maximum)
• Output current: 30 A continuous
• Active current limiting (chopping) with default threshold of 100 A (can be adjusted lower)
• Inputs compatible with 1.8 V, 3.3 V, and 5 V logic
• PWM operation up to 100 kHz
• On-board current sensor directly measures motor current
• Reverse-voltage protection
• Undervoltage shutdown
• Short circuit protection
• Size: 1.9″ × 1.7″
• Two 0.126″ mounting holes for #4 or M3 screws

G2 and H2 high-power motor driver versions

The following table provides a general comparison of the G2 and H2 drivers, which are available in six single-channel versions and eight dual-channel versions. Four of the dual-channel drivers have the form factor of an Arduino shield, but they can also be used with other controllers as general-purpose motor drivers. The other four dual-channel drivers are in the form factor of a Raspberry Pi HAT and compatible Raspberry Pi boards (Model B+ or newer). The single-channel G2 drivers all have the same form factor except for the highest-power 24v30, which is larger to accommodate the much larger MOSFETs. We also have a higher-voltage, single-channel H2 high-power motor driver with the same form factor as the single-channel G2 drivers, but the control interface and some aspects of the operation are different.

G2 and H2 High-Power Motor Drivers
	G2 18v17	G2 18v25	G2 24v13	G2 24v21	G2 24v30	H2 36v11	G2 18v18	G2 18v22	G2 24v14	G2 24v18
Motor channels:	single (1)						dual (2)
Min. operating voltage:	6.5 V					5 V	6.5 V
Absolute max. input voltage:	30 V		40 V			60 V	30 V		40 V
Max. nominal battery voltage:	18 V		28 V			36 V	18 V		28 V
Max. continuous current(1):	17 A	25 A	13 A	21 A	30 A	11 A	18 A	22 A	14 A	18 A
Current sense feedback?	20 mV/A	10 mV/A	40 mV/A	20 mV/A	13.2 mV/A	60 mV/A(2)	20 mV/A	10 mV/A	20 mV/A	20 mV/A
Default current limit:	40 A	60 A	30 A	50 A	100 A	—	50 A	60 A	40 A	50 A
Size:	1.3″ × 0.8″				1.7″ × 1.9″	1.3″ × 0.8″	2.56″ × 2.02″
Shield version available?:	—	—	—	—	—	—	Yes	Yes	Yes	Yes
Raspberry Pi expansion version available?:	—	—	—	—	—	—	Yes	Yes	Yes	Yes
1-piece price:	$44.95	$56.95	$44.95	$56.95	$74.95	$56.95	$74.95	$104.95	$79.95	$104.95
Note 1: Per motor channel, on Pololu carrier board, at room temperature, and without additional cooling.
Note 2: When VCC = 5 V; sensitivity is proportional to VCC.

Pololu G2 High-Power Motor Drivers 24v21 and 24v13.

Pololu G2 High-Power Motor Driver 24v30 CS. (1)

Pololu Dual G2 High-Power Motor Driver 24v14 Shield for Arduino.

Pololu Dual G2 High-Power Motor Driver 24v18 Shield for Arduino.

Pololu Dual G2 High-Power Motor Driver 18v18 for Raspberry Pi.

Pololu Dual G2 High-Power Motor Driver 18v22 for Raspberry Pi.

Note: As an alternative to these motor drivers, our Simple Motor Controllers have similar power characteristics and offer high-level interfaces (e.g. USB, RC hobby servo pulses, analogue voltages, and TTL serial commands) that make them easier to use for some applications.

Using the motor driver

Pinout

Connections

The motor and motor power connections are on one side of the board, and the control connections are on the other side. The motor supply should be capable of supplying high current. There are a variety of options for making the high-power connections (VIN, OUTA, OUTB, GND):

• The largest through-holes are 4 mm in diameter with 12.5 mm spacing. These can be used with #6 or M3.5 screws for attaching various types of lugs or solderless ring terminals, or thick wires up to 10 AWG can be soldered directly to the board.
• The slots above the large through-holes can accommodate a 4-pin terminal block or other connector with a pitch between 9.5 mm and 12 mm. Examples of compatible terminal blocks are the Amphenol YK4410403000G and Eaton CB30220407.
• Holes with 0.1″ and 0.2″ (5 mm) spacing are also available for connecting 0.1″-pitch headers or 5 mm-pitch terminal blocks, but please note that these smaller connection options are generally not suitable for the kinds of high currents this driver is intended for.

The control connections are designed to interface with 1.8 V to 5 V systems (5.5 V max), and they are arranged with a 0.1″ spacing that works with 0.1″ male headers and female headers and is compatible with solderless breadboards and perfboards. In a typical configuration, only PWM and DIR are required.

For good performance, it is important to install a large capacitor across the motor supply and ground close to the motor driver. We generally recommend using a capacitor of at least a few hundred μF and rated well above the maximum supply voltage; the required capacitance will be greater if the power supply is poor or far (more than about a foot) from the driver, and it will also depend on other factors like motor characteristics and applied PWM frequency. A through-hole capacitor can be installed directly on the board in the holes labelled '+' and '−' (connected to VM and GND, respectively); these holes are spaced to accommodate lead pitches of 3.5 mm, 5 mm, or 7.5 mm, depending on the specific pair used. The driver includes three on-board 33 µF polymer capacitors, which might be sufficient for brief tests and limited low-power operation, but adding a bigger capacitor is strongly recommended for most applications.

Warning: Take proper safety precautions when using high-power electronics. Make sure you know what you are doing when using high voltages or currents! During normal operation, this product can get hot enough to burn you. Take care when handling this product or other components connected to it.

Motor control options

With the PWM pin held low, both motor outputs will be held low (a brake operation). With PWM high, the motor outputs will be driven according to the DIR input. This allows two modes of operation: sign-magnitude, in which the PWM duty cycle controls the speed of the motor and DIR controls the direction, and locked-antiphase, in which a pulse-width-modulated signal is applied to the DIR pin with PWM held high.

In locked-antiphase operation, a low duty cycle drives the motor in one direction, and a high duty cycle drives the motor in the other direction; a 50% duty cycle turns the motor off. A successful locked-antiphase implementation depends on the motor inductance and switching frequency smoothing out the current (e.g. making the current zero in the 50% duty cycle case), so a high PWM frequency might be required.

PWM frequency

The motor driver supports PWM frequencies as high as 100 kHz, but note that switching losses in the driver will be proportional to the PWM frequency. Typically, around 20 kHz is a good choice for sign-magnitude operation since it is high enough to be ultrasonic, which results in quieter operation.

A pulse on the PWM pin must be high for a minimum duration of approximately 0.5 µs before the outputs turn on for the corresponding duration (any shorter input pulse does not produce a change on the outputs), so low duty cycles become unavailable at high frequencies. For example, at 100 kHz, the pulse period is 10 µs, and the minimum non-zero duty cycle achievable is 0.5/10, or 5%.

Current sensor

The G2 24v30 CS includes an Allegro ACS37220LEZATR-100B3 ±100A Hall effect current sensor on the OUTB motor output, and this sensor outputs a voltage proportional to the motor current and VCC voltage on the motor driver’s CS pin. The CS voltage, V_CS, is centred at 1.65 V when there is no current flowing and changes by approximately 13.2 mV per amp of motor current. Current flowing from OUTA to OUTB is considered positive and increases V_CS, while current flowing from OUTB to OUTA decreases V_CS:

``V_"OUT" = 1.65 text(V) + 0.0132 text(V)/text(A) * I_"A→B"``

``I_"A→B" = (V_"OUT" – 1.65 text(V)) / (0.0132 text(V)/text(A)) = (V_"OUT" – 1.65 text(V)) * 75.8 text(A)/text(V)``

For more details on the current sensor, see the ACS37220 datasheet (2MB pdf). We also have standalone carriers for this current sensor available in compact and large form factors.

Current limiting

The G2 driver has the ability to limit the motor current through current chopping: once the motor drive current reaches a set threshold, the driver goes into brake mode (slow decay) for about 25 µs before applying power to drive the motor again. This makes it more practical to use the driver with a motor that might only draw around ten amps while running but can draw many times that amount while starting.

The current limiting threshold is nominally set to about 100 A by default. You can lower the limit by connecting an additional resistor between the VREF pin and the adjacent GND pin; the graph below shows how the current limit relates to the VREF resistor value. For example, adding a 100 kΩ resistor between VREF and GND lowers the current limit to approximately 55 A. Note that the current limiting threshold is not very precise, and it is even less accurate at low settings (indicated by the dashed portion of the curve).

Fault conditions

The motor driver can detect several fault states that it reports by driving the FLT pin low; this is an open-drain output that should be pulled up to your system’s logic voltage. The detectable faults include short circuits on the outputs, under-voltage, and over-temperature. All of the faults disable the motor outputs but are not latched, meaning the driver will attempt to resume operation when the fault condition is removed (or after a delay of a few milliseconds in the case of the short circuit fault). The over-temperature fault provides a weak indication of the board being too hot, but it does not directly indicate the temperature of the MOSFETs, which are usually the first components to overheat, so you should not count on this fault to prevent damage from over-temperature conditions.

Real-world power dissipation considerations

The MOSFETs on this driver can handle large current spikes for short durations (e.g. 200 A for a few milliseconds), and the driver’s current chopping will help keep current spikes under 100 A or whatever lower limit has been set via VREF. The actual current you can deliver for longer durations than quick transients will depend on how well you can keep the driver cool, and the carrier’s printed circuit board is designed to help with this by drawing heat out of the MOSFETs. In our tests at room temperature and with no forced air flow, the driver was able to deliver 30 A for several minutes without the MOSFETs exceeding 125°C. Performance can be improved by adding a heat sink or forced air flow, and performance will be derated for operation in confined spaces or higher ambient temperatures.

Warning: This motor driver has no over-temperature shut-off, and an over-temperature condition can cause permanent damage to the motor driver. If you expect to be operating near the rated limits, we recommend monitoring the MOSFETs’ temperature and looking into adding additional cooling if necessary. We also recommend using the driver’s integrated current sensor to monitor your current draw.

Dimensions

General specifications

Identifying markings

Notes:

1

Absolute maximum; higher voltages can permanently destroy the motor driver. Recommended maximum is approximately 34 V, which leaves a safety margin for ripple voltage on the supply line.

2

Default current limiting threshold (can be adjusted lower).

File downloads

• Dimension diagram of the Pololu G2 High-Power Motor Driver 24v30 CS (315k pdf)

• 3D model of the Pololu G2 High-Power Motor Driver 24v30 CS (5MB step)

• Drill guide for the Pololu G2 High-Power Motor Driver 24v30 CS (250k dxf)

  This DXF drawing shows the locations of all of the board’s holes.