This discrete MOSFET stepper motor driver enables control of one bipolar stepper motor. It supports a wide 8 V to 50 V operating voltage range and can deliver up to 4 A continuous per phase without a heat sink or forced air flow (6 A max with sufficient additional cooling).
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The Pololu High-Power Stepper Motor Driver 36v4 combines the DRV8711 stepper motor driver IC from Texas Instruments with external MOSFETs to enable control of large bipolar stepper motors at operating voltages from 8 V to 50 V. The DRV8711 has many configurable settings, so please see the DRV8711 datasheet (3MB pdf) for a detailed explanation of its features and how to use them (we also have an Arduino library that simplifies getting started by providing basic functions for configuring and operating the driver).
The driver’s power performance is a function of the external dual H-bridges, which allow the driver to deliver continuous currents up to 4 A per phase without any additional cooling such as heat sinks or forced airflow. (With sufficient additional cooling, the driver can support currents up to around 6 A per phase; see the Power dissipation considerations section below for more information, including important information about using this product safely.)
This product ships with all surface-mount components installed as shown in the product picture. However, soldering is required for assembly of the included through-hole parts. The following through-hole parts are included:
The 0.1″ male headers can be broken or cut into smaller pieces as desired and soldered into the smaller through-holes. These headers are compatible with solderless breadboards, 0.1″ female connectors, and our premium and pre-crimped jumper wires. The terminal blocks can be soldered into the larger holes to allow for convenient temporary connections of unterminated power and motor wires (see our short video on terminal block installation). You can also solder your motor leads and other connections directly to the board for the most compact installation.
|VIN||8 V to 50 V board power supply connection (reverse-protected up to 40 V).|
|VM||This pin gives access to the motor power supply after the reverse-voltage protection MOSFET (see the board schematic at the bottom of this page). It can be used to supply reverse-protected power to other components in the system. This pin can also be used with the adjacent GND pin to add an external electrolytic capacitor in systems where additional bypass capacitance would be helpful.|
|GND||Ground connection points for the motor power supply and control ground reference.|
|AOUT1||Motor output: “positive” end of phase A-coil.|
|AOUT2||Motor output: “negative” end of phase A-coil.|
|BOUT1||Motor output: “positive” end of phase B coil.|
|BOUT2||Motor output: “negative” end of phase B coil.|
|V5 (OUT)||Regulated 5 V output: this pin gives access to the voltage from the internal regulator of the DRV8711. The regulator can only provide up to 10 mA, so it is primarily only useful for hard-wiring board inputs high and powering pull-ups for the board’s open-drain outputs. It is generally not intended for powering external devices.|
|IOREF||All of the board signal outputs (except BEMF) are open-drain outputs that are pulled up to IOREF, so this pin should be supplied with the logic voltage of the controlling system (e.g. 3.3 V for use in 3.3 V systems). For convenience, it can be connected to the neighboring V5 (OUT) pin when it is being used in a 5 V system.|
|STEP/AIN1||Changes in this input move the motor current one step up or down in the translator table (even when the motor is disabled). Stepping can also be controlled through the SPI interface, so this pin is optional. In external PWM mode, this pin functions as AIN1 rather than STEP and directly controls the state of the AOUT1 output.|
|DIR/AIN2||Input that determines the direction of stepper motor rotation. The direction can also be controlled through the SPI interface, so this pin is optional. In external PWM mode, this pin functions as AIN2 rather than DIR and directly controls the state of the AOUT2 output.|
|SDATO||SPI data output. (This pin is also often referred to as “MISO”.) This pin is an open-drain output and is pulled up to IOREF on the board.|
|SDATI||SPI data input. (This pin is also often referred to as “MOSI”.)|
|SCLK||SPI clock input.|
|SCS||SPI chip select input. Logic transitions on this pin are required for SPI communication, even if this is the only device on the SPI bus.|
|SLEEP||By default, the driver pulls this pin low, which puts it in a low-power sleep mode where the motor driver circuitry is disabled and all-analog circuitry is placed into a low-power state. The digital circuitry still operates in sleep mode, so the device registers can still be accessed via the serial interface. This pin must be driven high to enable the device.|
|RESET||Chip reset input. A logic high on this input resets all internal logic, including the indexer and device registers, and disables the driver outputs. Note: the RESET pin does not function while the device is in sleep mode.|
|FAULT||The open-drain output that drives low when an over-current, pre-driver, over-temperature, or under-voltage fault is occurring. This pin is pulled up to IOREF, making it high by default.|
|BIN1||In external PWM mode, BIN1 directly controls the state of the BOUT1 output. This pin is not used in indexer mode (i.e. when using this device as a stepper motor driver).|
|BIN2||In external PWM mode, BIN2 directly controls the state of the BOUT2 output. This pin is not used in indexer mode (i.e. when using this device as a stepper motor driver).|
|STALL/BEMFV||The open-drain output is pulled up to IOREF on the board. In internal stall detect mode, output goes low when a stall is detected. In external stall detect mode, output goes low when a valid back-EMF measurement is available.|
|BEMF||An analog output that represents the motor back EMF. The signal on this pin can be further processed by a microcontroller to implement more advanced control and stall detection algorithms.|
Typical wiring diagram for connecting a microcontroller to a Pololu High-Power Stepper Motor Driver 36v4.
While the High-Power Stepper Motor Driver 36v4 allows control of a stepper motor through a simple step and direction interface, it first needs to be enabled and configured through its SPI interface. This means that the controlling microcontroller must be capable of acting as an SPI master (either with an SPI peripheral or software SPI), and it must be connected to the SDATI, SCLK, and SCS pins. While the SDATO and FAULT pins are not required to use this driver, it is generally a good practice to use them to monitor for error conditions.
Typical wiring diagram for connecting a microcontroller with a logic voltage of 5 V to a Pololu High-Power Stepper Motor Driver 36v4.
The High-Power Stepper Motor Driver 36v4 has an internal 5 V regulator that can be used to supply IOREF in cases where the board is being used in 5 V systems. We provide a shorting block for connecting V5 to IOREF, or for a more compact connection, you can bridge the surface mount jumper located next to those pins (highlighted in the picture below).
Surface mount jumper for V5 and IOREF pins on the Pololu High-Power Stepper Motor Driver 36v4.
Controlling a Pololu High-Power Stepper Motor Driver 36v4 with an Arduino-compatible #3104 A-Star 32U4 Mini SV.
We have written a High-Power Stepper Motor Driver library for Arduino that provides basic functions for configuring and operating the driver using an Arduino or Arduino-compatible controller. The library includes several example sketches.
The High-Power Stepper Motor Driver 36v4 can deliver up to 4 A continuous per phase under typical conditions, but the actual current it can deliver will depend on how well you can keep the module cool. The driver’s printed circuit board is designed to draw heat out of the MOSFETs, but performance can be improved by adding a heat sink or forced airflow. (Conversely, performance will be reduced in applications that limit heat dissipation, such as high ambient temperatures or operation in enclosures.) With sufficient additional cooling, the driver can deliver up to 6 A per phase before exceeding the 1 W power ratings of the 30 mΩ current sense resistors.
Warning: This motor driver has no meaningful over-temperature shut-off (while the DRV8711 IC has over-temperature protection, it is the external MOSFETs that will overheat first). An over-temperature condition can cause permanent damage to the motor driver. We strongly recommend you do not increase the current limit setting beyond 4 A (or lower in applications with reduced heat dissipation) unless you can first confirm that the temperature of the MOSFETs will stay under 140°C.
Note: When the driver powers up, the current limit setting defaults to the maximum (~18 A). Make sure you set it to something appropriate for both your stepper motor and the driver before activating the outputs!
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.
The driver’s current limit is set through its SPI interface. You can confirm you have set it correctly by using a multimeter to measure the actual current through one of the coils while the stepper motor is in full-step mode and not stepping. The current you measure this way will be approximately 70% of the set limit. Since the input voltage to the driver can be significantly higher than the coil voltage, the measured current on the power supply can be quite a bit lower than the coil current (the driver and coil basically act like a switching step-down power supply). Also, if the supply voltage is very high compared to what the motor needs to achieve the set current, the duty cycle will be very low, which also leads to significant differences between average and RMS currents.
Schematic diagram of the Pololu High-Power Stepper Motor Driver 36v4.