This design is available with a number of pin-compatible drivers, and it can be used with supply voltages from 8 to 42 volts, depending on the model. Drivers are available for output current up to 2.5 A, with stepping modes down to 1/16th step, and support uni- and bipolar stepper motors. You can also adjust current limits and current decay to optimize motor performance for the end application.
The STEPMO_EVK_206 and BD63720AEFV
For this demo, I have the STEPMO_EVK_206, which is based on the BD63720AEFV driver IC. It can operate from 19 to 28 V, which I’ll supply through this blue terminal. On the opposite side, these blue terminals provide connection to the motor. There’s also this potentiometer, which allows us to change the Vref used in setting the current limit, with the BD63720AEFV capable of a two amp output. There’s also a set of headers in the corner. The three-pin header lets you select preset fast, mixed, or slow decay modes, or you can apply an external analog voltage for precise tuning of current decay.
Figure 1. BD63720AEFV block diagram
The second set of headers allows you to set the device as master or slave, as the kit is stackable to support driving two motors at the same time. The driver itself has a low ON resistance DMOS output, an internal regulator for the low-power logic, and a noise masking function that allows for a constant-current drive without an external filter.
Performing a Demo
For the demo, I have both shields stacked and a motor connected to each. ROHM provides an Arduino library with examples, including the two board example I have loaded, as well as an EVK manual, CAD and design files, and additional documentation. You can see this list of defines, with the one for these boards uncommented. If you’re using a different version of the EVK, you leave that define statement uncommented, keep the others commented out and you’re all set, so you can easily move between the different drivers. From there, we set up the master and slave boards, pull their ENABLE and PS pins high and then get into the main code where it will go through various stepping modes, clock speeds, and directions.
Once I finish my evaluation and prototyping with this board, there’s a whole set of boards based on pin-compatible ROHM driver ICs. So if your application requirements change, you can easily repeat the evaluation with another EVK in the series by dropping that new IC into your design to address a different voltage range, finer stepping, or a more cost optimized solution without redesigning the board.
To learn more about ROHM’s family of stepper motor driver evaluation kits, visit ROHM.com.
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