This is a breakout board for TI’s DRV8824 microstepping bipolar stepper motor driver, a lower-current version of the DRV8825.
This product is a carrier board or breakout board for TI’s DRV8824 stepper motor driver; we therefore recommend careful reading of the DRV8824 datasheet (1MB pdf) before using this product. This stepper motor driver lets you control one bipolar stepper motor at up to 1.2 A output current per coil (see the Power Dissipation Considerations section below for more information). Here are some of the driver’s key features:
We also carry a DRV8825 stepper motor driver carrier that can serve as a direct, higher-power substitute for the DRV8824 carrier. The DRV8825 can deliver up to 1.5 A per coil without a heat sink (2.2 A max with sufficient additional cooling). The only way to tell our DRV8824 carrier apart from the DRV8825 carrier is by the markings on the driver IC; if you have a mix of the two, you might consider marking them (there is a blank square on the bottom silkscreen you can use for this).
Note that we carry several other stepper motor drivers that can be used as alternatives for this module (and drop-in replacements in many applications):
This product ships with all surface-mount components—including the DRV8824 driver IC—installed as shown in the product picture.
Some unipolar stepper motors (e.g. those with six or eight leads) can be controlled by this driver as bipolar stepper motors. For more information, please see the frequently asked questions. Unipolar motors with five leads be used with this driver.
The DRV8824 stepper motor driver carrier ships with one 1×16-pin breakaway 0.1" male header. The headers can be soldered in for use with solderless breadboards or 0.1" female connectors. You can also solder your motor leads and other connections directly to the board.
Caution: Installing the header pins so that the silkscreen side is up and the components are down can limit the range of motion of the trimpot used to set the current limit. If you plan on installing the header pins in this orientation, please set the current limit before soldering in the pins.
|Minimal wiring diagram for connecting a microcontroller to a DRV8824/DRV8825 stepper motor driver carrier (full-step mode).|
The driver requires a motor supply voltage of 8.2 – 45 V to be connected across VMOT and GND. This supply should have appropriate decoupling capacitors close to the board, and it should be capable of delivering the expected stepper motor current.
Warning: This carrier board uses low-ESR ceramic capacitors, which makes it susceptible to destructive LC voltage spikes, especially when using power leads longer than a few inches. Under the right conditions, these spikes can exceed the 45 V maximum voltage rating for the DRV8824 and permanently damage the board, even when the motor supply voltage is as low as 12 V. One way to protect the driver from such spikes is to put a large (at least 47 µF) electrolytic capacitor across motor power (VMOT) and ground somewhere close to the board.
Four, six, and eight-wire stepper motors can be driven by the DRV8824 if they are properly connected; a FAQ answer explains the proper wirings in detail.
Warning: Connecting or disconnecting a stepper motor while the driver is powered can destroy the driver. (More generally, rewiring anything while it is powered is asking for trouble.)
Stepper motors typically have a step size specification (e.g. 1.8° or 200 steps per revolution), which applies to full steps. A microstepping driver such as the DRV8824 allows higher resolutions by allowing intermediate step locations, which are achieved by energizing the coils with intermediate current levels. For instance, driving a motor in quarter-step mode will give the 200-step-per-revolution motor 800 microsteps per revolution by using four different current levels.
The resolution (step size) selector inputs (MODE0, MODE1, and MODE2) enable selection from the six step resolutions according to the table below. All three selector inputs have internal 100kΩ pull-down resistors, so leaving these three microstep selection pins disconnected results in full-step mode. For the microstep modes to function correctly, the current limit must be set low enough (see below) so that current limiting gets engaged. Otherwise, the intermediate current levels will not be correctly maintained, and the motor will skip microsteps.
Each pulse to the STEP input corresponds to one microstep of the stepper motor in the direction selected by the DIR pin. These inputs are both pulled low by default through internal 100kΩ pull-down resistors. If you just want rotation in a single direction, you can leave DIR disconnected.
The chip has three different inputs for controlling its power states: RESET, SLEEP, and ENBL. For details about these power states, see the datasheet. Please note that the driver pulls the SLEEP pin low through an internal 1MΩ pull-down resistor, and it pulls the RESET and ENBL pins low through internal 100kΩ pull-down resistors. These default RESET and SLEEP states are ones that prevent the driver from operating; both of these pins must be high to enable the driver (they can be connected directly to a logic “high” voltage between 2.2 and 5.25 V, or they can be dynamically controlled via connections to digital outputs of an MCU). The default state of the ENBL pin is to enable the driver, so this pin can be left disconnected.
The DRV8824 also features a FAULT output that drives low whenever the H-bridge FETs are disabled as the result of over-current protection or thermal shutdown. The carrier board connects this pin to the SLEEP pin through a 10k resistor that acts as a FAULT pull-up whenever SLEEP is externally held high, so no external pull-up is necessary on the FAULT pin. Note that the carrier includes a 1.5k protection resistor in series with the FAULT pin that makes it is safe to connect this pin directly to a logic voltage supply, as might happen if you use this board in a system designed for the pin-compatible A4988 carrier. In such a system, the 10k resistor between SLEEP and FAULT would then act as a pull-up for SLEEP, making the DRV8824 carrier more of a direct replacement for the A4988 in such systems (the A4988 has an internal pull-up on its SLEEP pin). This 10k resistor is not present on the initial (md20a) version of the DRV8825 carrier. To keep faults from pulling down the SLEEP pin, any external pull-up resistor you add to the SLEEP pin input should not exceed 4.7k.
To achieve high step rates, the motor supply is typically much higher than would be permissible without active current limiting. For instance, a typical stepper motor might have a maximum current rating of 1 A with a 5Ω coil resistance, which would indicate a maximum motor supply of 5 V. Using such a motor with 12 V would allow higher step rates, but the current must actively be limited to under 1 A to prevent damage to the motor.
The DRV8824 supports such active current limiting, and the trimmer potentiometer on the board can be used to set the current limit. You will typically want to set the driver’s current limit to be at or below the current rating of your stepper motor. One way to set the current limit is to put the driver into full-step mode and to measure the current running through a single motor coil without clocking the STEP input. The measured current will be 0.7 times the current limit (since both coils are always on and limited to approximately 70% of the current limit setting in full-step mode).
Another way to set the current limit is to measure the voltage on the “ref” pin and to calculate the resulting current limit (the current sense resistors are 0.330Ω). The ref pin voltage is accessible on a via that is circled on the bottom silkscreen of the circuit board. The current limit relates to the reference voltage as follows:
Current Limit = VREF × 0.61
So, for example, if you have a stepper motor rated for 0.5 A, you can set the current limit to 0.5 A by setting the reference voltage to 0.82 V.
Note: The coil current can be very different from the power supply current, so you should use the current measured at the power supply to set the current limit. The appropriate place to put your current meter is in series with one of your stepper motor coils.
The DRV8824 driver IC has a maximum current rating of 1.6 A per coil, but the current sense resistors further limit the maximum current to 1.2 A, and the actual current you can deliver depends on how well you can keep the IC cool. The carrier’s printed circuit board is designed to draw heat out of the IC, but to supply more than approximately 0.75 A per coil, a heat sink or other cooling method is required.
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.
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. Additionally, please note that the coil current is a function of the set current limit, but it does not necessarily equal the current limit setting. The actual current through each coil changes with each microstep. See the DRV8824 datasheet for more information.
|Schematic diagram for the DRV8824/DRV8825 stepper motor driver carrier.|
The current sense resistors (R2 and R3) on the DRV8825 carrier are 0.330 Ω. This schematic is also available as a downloadable pdf (196k pdf).
The DRV8824 carrier was designed to be as similar to our A4988 stepper motor driver carriers as possible, and it can be used as a drop in replacement for the A4988 carrier in many applications because it shares the same size, pinout, and general control interface. There are a few differences between the two modules that should be noted, however:
In summary, the DRV8824 carrier is similar enough to our A4988 carriers that the minimum connection diagram for the A4988 is a valid alternate way to connect the DRV8824 to a microcontroller as well:
|Alternative minimal wiring diagram for connecting a microcontroller to a DRV8824/DRV8825 stepper motor driver carrier (full-step mode).|
|Size:||0.6″ × 0.8″|
|Minimum operating voltage:||8.2 V|
|Maximum operating voltage:||45 V|
|Continuous current per phase:||0.75 A2|
|Maximum current per phase:||1.2 A3|
|Minimum logic voltage:||2.5 V4|
|Maximum logic voltage:||5.25 V4|
|Microstep resolutions:||full, 1/2, 1/4, 1/8, 1/16, and 1/32|
|Reverse voltage protection?:||N|
Yes. To avoid damaging your stepper motor, you want to avoid exceeding the rated current, which is 600 mA in this instance. The DRV8825 stepper motor drivers let you limit the maximum current, so as long as you set the limit below the rated current, you will be within spec for your motor, even if the voltage exceeds the rated voltage. The voltage rating is just the voltage at which each coil draws the rated current, so the coils of your stepper motor will draw 600 mA at 3.9 V. By using a higher voltage along with active current limiting, the current is able to ramp up faster, which lets you achieve higher step rates than you could using the rated voltage.
If you do want to use a lower motor supply voltage (under 8 V) for other reasons, consider using our DRV8834 low-voltage stepper motor driver carrier.
Yes, you do! Setting the current limit on your stepper motor driver carrier before connecting your motor is essential to making sure that it runs properly. An appropriate current limit also ensures that your motor is not allowed to draw more current than it or your driver can handle, since that is likely to damage one or both of them.
Setting the current limit on our A4988, DRV8825, DRV8824, DRV8834, and DRV8880 stepper motor driver carriers is done by adjusting the on-board potentiometer. We strongly recommend using a multimeter to measure the VREF voltage while setting the current limit so you can be sure you set it to an appropriate value (just turning the pot randomly until things seem to work is not a good approach). The following video has more details on setting the current limit:
Measuring the current draw at the power supply does not necessarily provide an accurate measure of the coil current. 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: RMS current is what is relevant for power dissipation in the chip but many power supplies won’t show that. You should base your assessment of the coil current on the set current limit or by measuring the actual coil currents.
Please note that while the DRV8824 driver IC is rated for up to 1.6 A per coil, the 0.5 W current sense resistors are only rated for 1.2 A, and the chip by itself will overheat at lower currents. We have found that it generally requires a heat sink to deliver more than approximately 0.75 A per coil, but this number depends on factors such as ambient temperature and air flow. For example, sealing three DRV8824 driver carriers in close proximity in a small box will cause them to overheat at lower currents than a unit by itself in open air.
The answer to this question depends on the type of stepper motor you have. When working with stepper motors, you will typically encounter two types: unipolar stepper motors and bipolar stepper motors. Unipolar motors have two windings per phase, allowing the magnetic field to be reversed without having to reverse the direction of current in a coil, which makes unipolar motors easier to control than bipolar stepper motors. The drawback is that only half of the phase is carrying current at any given time, which decreases the torque you can get out of the stepper motor. However, if you have the appropriate control circuitry, you can increase the stepper motor torque by using the unipolar stepper motor as a bipolar stepper motor (note: this is only possible with 6- or 8-lead unipolar stepper motors, not with 5-lead unipolar stepper motors). Unipolar stepper motors typically have five, six, or eight leads.
Bipolar steppers have a single coil per phase and require more complicated control circuitry (typically an H-bridge for each phase). The DRV8824/DRV8825 has the circuitry necessary to control a bipolar stepper motor. Bipolar stepper motors typically have four leads, two for each coil.
|Two-phase bipolar stepper motor with four leads.|
The above diagram shows a standard bipolar stepper motor. To control this with the DRV8824/DRV8825, connect stepper lead A to board output A1, stepper lead C to board output A2, stepper lead B to board output B1, and stepper lead D to board output B2. See the DRV8824 or DRV8825 datasheet for more information.
If you have a six-lead unipolar stepper motor as shown in the diagram below:
|Two-phase unipolar stepper motor with six leads.|
you can connect it to the DRV8824/DRV8825 as a bipolar stepper motor by making the bipolar connections described in the section above and leaving stepper leads A’ and B’ disconnected. These leads are centre taps to the two coils and are not used for bipolar operation.
If you have an eight-lead unipolar stepper motor as shown in the diagram below:
|Two-phase unipolar stepper motor with eight leads.|
you have several connection options. An eight-lead unipolar stepper motor has two coils per phase, and it gives you access to all of the coil leads (in a six-lead unipolar motor, lead A’ is internally connected to C’ and lead B’ is internally connected to D’). When operating this as a bipolar stepper, you have the option of using the two coils for each phase in parallel or in series. When using them in parallel, you decrease coil inductance, which can lead to increased performance if you have the ability to deliver more current. However, since the DRV8824/DRV8825 actively limits the output current per phase, you will only get half the phase current flowing through each of the two parallel coils. When using them in series, it’s like having a single coil per phase (like in four-lead bipolar steppers or six-lead unipolar steppers used as bipolar steppers). We recommend you use a series connection.
To connect the phase coils in parallel, connect stepper leads A and C’ to board output A1, stepper leads A’ and C to board output A2, stepper leads B and D’ to board output B1, and stepper leads B’ and D to board output B2.
To connect the phase coils in series, connect stepper lead A’ to C’ and stepper lead B’ to D’. Stepper leads A, C, B, and D should be connected to the stepper motor driver as normal for a bipolar stepper motor (see the bipolar stepper connections above).