DRV8434S SPI Stepper Motor Driver Carrier, Potentiometer for Max. Current Limit
This breakout board for TI’s DRV8434S microstepping bipolar stepper motor driver operates from 4.5 V to 48 V and can deliver up to approximately 1.2 A continuous per phase without a heat sink or forced air flow (2 A peak). The SPI interface allows configuration of the current limit, step mode (11 step modes from full-step through 1/256-step), decay mode, and stall detection. The driver also features built-in protection against under-voltage, over-current, and over-temperature conditions. This version of the board uses an on-board potentiometer for setting the maximum current limit, and SPI can be used to set the actual current limit to intermediate values in increments of the set maximum/16.
Alternatives available with variations in these parameter(s): current limit control header pins soldered?
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- I want to control a 3.9 V, 600 mA bipolar stepper motor, but this driver has a minimum operating voltage above 3.9 V. Can I use this driver without damaging the stepper motor?
Yes. To avoid damaging your stepper motor, you want to avoid exceeding the rated current, which is 600 mA in this instance. All of our 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.
- Do I really need to set the current limit on my stepper motor driver before using it, and if so, how do I do it?
Yes, you do! Setting the current limit on your stepper motor driver carrier 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.
For the DRV8434A Stepper Motor Driver Carrier the current limit is set by adjusting the board’s 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:
Setting the current limit on the DRV8434S SPI Stepper Motor Driver Carrier, 2A Max. Current Limit is done through its SPI interface (this is very different from most of our other stepper motor driver carriers, which have their current limits set through their on-board potentiometers). The DRV8434S SPI Stepper Motor Driver Carrier, 2A Max defaults to its maximum possible current limit setting on start-up, which is much more current than the board can safely deliver, so you will need to set the current limit to an appropriate value for your stepper motor before enabling the driver outputs to prevent damage to the board. This is done by adjusting the TRQ_DAC bits in the CTRL1 register. The DRV8434S datasheet has more information on how to set the current limit through the SPI interface, and our Arduino library includes example sketches showing how to implement this in software.
For the DRV8434S SPI Stepper Motor Driver Carrier, Potentiometer for Max Current Limit, the current limit can be adjusted through both the onboard potentiometer and SPI. If the TRQ_DAC scaling factor at its left at its default of 100%, the potentiometer can be used alone to set the current limit, like with the DRV8434A. Otherwise, the TRQ_DAC value set through SPI is used to further scale the current limit set with the potentiometer.
- My stepper motor driver is overheating, but my power supply shows it’s drawing significantly less than the continuous current rating listed on the product page. What gives?
- 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.
- How do I connect my stepper motor to the DRV8434x stepper motor driver carrier?
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 DRV8434x drivers have 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 DRV8434x, connect stepper leads A and C to board outputs A1 and A2, respectively, and stepper leads B and D to board outputs B1 and B2, respectively. Note that if you happen to swap which way the wires are connected for any coil, the stepper motor will turn in the opposite direction, and if you happen to pair up wires from different coils, the motor should be noticeably erratic when you try to step it, if it even moves at all. See the DRV8434x 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 DRV8434x 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 center 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 DRV8434x 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).