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Brushed DC Servo Drive | Hakadi


Brushless DC motors and their associated drive electronics tend to be expensive and complex. [Ottoragam] Was looking for a cheaper alternative and built this brushed DC motor servo controller and the results look very promising. Check out the video after the break.

He needed a low-cost closed-loop driver for his home-made CNC controller. The servo drive is capable of delivering up to 7 A continuous current to a brushed DC motor at voltages up to 36 V, which is approximately 250 W or 1/3 HP. It uses feedback from quadrature encoders for closed-loop control. This driver accepts simple STEP and DIRECTION signals, allowing it to be easily interfaced with a microcontroller and used as a replacement for stepper motors in positioning applications. All control is handled by the ATmega328P. It obtains input signals and encoder data, performs PID control, and drives the motor through the DRV8701 full-bridge MOSFET driver. There are also some false detections for motor overcurrent and drive undervoltage. Four IRFH7545 MOSFETs in H-bridge configuration form the output power stage.

This work is still in progress and [Ottoragam] There are a few features on his wish list that are pending. Important ones include adding a serial interface to facilitate tuning of PID parameters and creating a GUI to make tuning easier. The project is open source and all original files can be found in his Github repository. The board is mostly surface mount, but the passive components are all 0805, so it should be easy to assemble. The QFN packaging of the microcontroller may be the only thorny issue. [Ottoragam] Hopefully he’ll have some beta testers on his board and maybe some useful input to improve his design.



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