Unlike AC motors, DC motors are very easy to use because their speed can be changed easily. So, how is this achieved in practice? As DC motors generate torque by a reaction between two magnetic fields: one field established by stationary “field” windings (coils), and the other by windings in the rotating armature. Some DC motors lack field windings, substituting large permanent magnets in their place so that the stationary magnetic field is constant for all operating conditions.
In any case, the operating principle of a DC electric motor is that currently passed through the armature creates a magnetic field that tries to align with the stationary magnetic field. This causes the armature to rotate. This DC motor speed control circuit is designed using IC LM3578 switching regulator, it can be used for DC to DC voltage conversions such as buck, boost, and inverting applications.
Hardware Required
| S.no | Component | Value | Qty |
|---|---|---|---|
| 1. | IC | LM3578 | 1 |
| 2. | MOSFET | IRF540 | 1 |
| 3. | Diode | 1N4001 | 1 |
| 4. | Resistor | 120KΩ,100KΩ,4.7KΩ | 1,1,1 |
| 5. | Variable Resistor | 220KΩ | 1 |
| 6. | Capacitor | 0.1uF,470uF,22pF | 1,1,1 |
| 7. | Motor | – | 1 |
| 8. | Connecting Wires | – | – |
Circuit Diagram
Working Explanation
As we can see in the circuit, the DC motor is connected to the DC power supply and output driver IRF 540 MOSFET. Here a diode D1 is placed to provide protection from back emf. The further output signal from pin5 of LM3578 is fed to the gate terminal of MOSFET, it drives the MOSFET. Now the LM3578 IC’s Pins 8, 7, and 6 are shorted together and connected with a positive supply. And components C1, C2, and R2 are connected between pins 1, 3, and the ground supply. Here pin 2 of LM3578 is connected with R1 and variable resistor VR1. We can vary the speed of the DC motor by varying this VR1.
IRF540 Pinout
Applications
- Can be used in centrifugal and reciprocating pumps
- Can be used in conveyors, hoists, elevators, and electric Locomotives
- Also can be used in blowers, fans, drilling machines, milling machines, and machine tools
