DC Motor Speed Controller

Required devices:

1. 3v - 12v dc motor

2. 100k potentiometer

3. MOSFET TO-220AB

4. 12v battery

How to connect?

Connect Drain (D) of MOSFET and right end of potentiometer (P) to the +ve terminal of battery. Connect Source (S) of MOSFET to the one end of motor. Connect another end of motor and another end of 'P' to the –ve terminal of battery. Finally, connect the middle point of 'P' to the Gate (G) of MOSFET. Now you can control the speed of motor by rotating the knob of potentiometer.

NOTE: 
The MOSFET should be N channel enhancement  MOSFET (IRF540, IRF3205,...).
The supply voltage depend on MOSFET and the motor. Example: If the MOSFET is designed for 12v and capable of 50v. The supply voltage should be 12v.

BRUSHLESS VS BRUSHED MOTORS

1. Brush-less Motor:  DC Brush-less Motor uses a permanent magnet external rotor, three phases of driving coils, one or more Hall effect devices to sense the position of the rotor, and the associated drive electronics.

2. Brushed Motor: A Brushed Motor has a rotating set of wound wire coils called an armature which acts as an electromagnet with two poles. A mechanical rotary switch called a commutator reverses the direction of the electric current twice every cycle, to flow through the armature so that the poles of the electromagnet push and pull against the permanent magnets on the outside of the motor.

Brush-less DC Motor Pros

• Electronic commutation based on Hall position sensors
• Less required maintenance due to absence of brushes
• Speed/Torque- flat, enables operation at all speeds with rated load
• High efficiency, no voltage drop across brushes
• High output power/frame size.
  Reduced size due to superior thermal characteristics. Because BLDC has the winding on the starter, which is connected to the case, the heat dissipation is better
• Higher speed range - no mechanical limitation imposed by brushes/commutator
• Low electric noise generation

Brushed DC Motor Pros
Two wire control
Replaceable brushes for extended life
Low cost of construction
Simple and inexpensive control
No controller is required for fixed speeds
Operates in extreme environments due to lack of electronics