Mechatronics, Industrial Control & Instrumentation

DC Motor Power Op-amp Speed Controller

Let’s consider the functional diagram below:

DC motor power op-amp speed controller functional diagram
Figure 1 DC motor power op-amp speed controller functional diagram

The D/A converter outputs a voltage directly related to the potentiometer position. However, the D/A converter’s output current is limited and not enough to drive a motor.  A power operational amplifier (op-amp) circuit, configured as a noninverting amplifier can drive the motor at the higher currents required. In effect, the power amp will serve as a buffer between the D/A converter and the motor.

The circuit below shows the components used along with their interconnections.

Figure 2 Circuit showing op-amp (OPA 547) between the D/A converter and the dc motor

The OPA 547 can be powered by a bipolar (±) 9 V supply instead of a standard bipolar 15 V supply. With an input resistor of 10 kꭥ and a feedback resistor of 1 kꭥ, the power amp circuit has a gain of 1.1, therefore, the voltage from the D/A converter is not amplified a lot, but the circuit is able to source ample current to the dc motor.

You can also read: Pulse Width Modulation (PWM) Speed Control of a DC motor

John Mulindi

John Mulindi is an Industrial Instrumentation and Control Professional with a wide range of experience in electrical and electronics, process measurement, control systems and automation. In free time he spends time reading, taking adventure walks and watching football.

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