Here is an inexpensive yet versatile solution for interfacing dc motors with microcontrollers. The circuit, designed to provide bidirectional drive currents, uses TTL compatible quadruple high-current half-H drivers to drive inductive loads such as electromagnetic relays, plungers, dc and bipolar stepper motors, as well as other high-current/high-voltage loads. With this circuit you can interface two dc motors which can be controlled in both clockwise (cw) and counterclockwise (ccw) directions. Similarly, if you want only a fixed direction of motor rotation then you can make use of all the four channels to connect up to four dc motors. This high voltage, high current four channel motor driver module is configured to accept standard TTL/DTL logic level inputs. The onboard regulated 5 V (0.5A) dc supply output reserved for the external logic/microcontroller circuitry obviates the requirement of a separate uC-power supply.
Tried and tested schematic diagram of the modular motor driver, designed around the dual H-Bridge motor driver chip L293D, is shown below (see fig 1) . According to datasheet, the L293D is designed to provide bidirectional drive currents of up to 600-mA at voltages from 4.5 V to 36 V. Here, the presented circuit is configured to operate by an input supply voltage level upto 35V DC (see datasheets of IC1 & IC2). Further, as an (optional) enhancement, total 5 LEDs are used for visual indication of the power, and motor control logic status. Circuit diagram of this is given as a separate one (see fig 2).
Note: To control the speed of dc motors, feed pwm output from the relevant microcontroller to enable pins (EN1 & EN2) linked to input sockets J1 and J2.