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The project presented here is a low-cost position control closed-loop analog-servo using brushed DC motor and potentiometer as feedback. This project provides all necessary active functions for a closed-loop servo system using a Brushed DC Motor and potentiometer mounted on the output shaft of the DC Motor with Gear. The project is ideally suited for almost any servo positioning application. Can be used in applications such as side mirror movement control for cars, car head lamp beam control, animatronics, robotics, etc.

The project requires a special mechanism, where the DC motor’s output shaft is mechanically couple with the potentiometer shaft using a reduction gear. Approx. reduction ratio 15-50: 1. When the reference pot is turned, the motor shaft will follow the potion. This will provide a maximum rotation of 270 degrees. Multi rotation is possible with the help of a multiturn potentiometer.

The project is based on the ZXBM5409Q chip from Diode Incorporation which is a protected H-bridge driver designed specifically for manual automotive headlight-beam control and industrial servo control applications with DC-brush motor loads. The integrated full-bridge driver output stage is composed of high-current, low-RDSON H-bridge MOSFETs to maximize efficiency. To simplify the circuit design and minimize external components, the device integrates voltage and temperature-compensated internal references, amplifiers, and output H-bridge power switches with low RDSON. For system flexibility, the servo controls forward and reverse hysteresis, dead band, and angle amplification are easily programmable by external resistors. To help protect the motor coil, the ZXBM5409Q provides fault condition protection, such as RANGE input short to GND, short-to supply voltage, or broken wires, by stopping the motor and disconnecting the output stage. In case of supply undervoltage and overvoltage, the device shuts down the output drive to help prevent overvoltage stress on the coil. The overcurrent protection monitors the output current and shuts down the outputs stage with periodic retry to help protect the coil from device burnout. Overtemperature shutdown provides thermal protection for the device.”

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