Simple 6V DC Motor Speed Controller Circuit using IC CD 40106

A simple and effective circuit to control the speed of a 6V DC motor can be made using the IC CD 40106.

This design lets you change the motors speed by adjusting the duty cycle of the input voltage making it a practical way to control speed.

This Simple 6V DC Motor Speed Controller Circuit using IC CD 40106 is easy to build and inexpensive, which makes it great for things like toy motors, small handheld fans, and little blowers.

The main part of this circuit is the IC CD 40106 Schmitt trigger inverter, which creates a PWM (Pulse Width Modulation) signal.

This signal is then used to control the motors speed with a transistor switch, providing smooth and quick adjustments.

Circuit Working:

Parts List:

Component	Specification	Quantity
Resistors	22k 1/4W	1
Potentiometer	100k	1
Capacitors	Ceramic 0.1µF	1
	Electrolytic 220µF 25V	1
Semiconductors	IC CD 40106	1
	Transistor 2N2222	1
	Diodes 1N4007	3
	6V DC Motor	1

The way this circuit works is based on a method called Pulse Width Modulation PWM.

This technique helps control the average voltage sent to the motor by changing the duty cycle of a square wave signal.

To create the PWM signal the circuit uses a IC CD 40106 Schmitt trigger NOT gate inverters.

The Schmitt trigger NOT gate inverters N1 is configured as PWM control oscillator.

The PWM control output from N1 is applied to the common inputs of N2 to N6 Schmitt trigger NOT gate inverters.

The common outputs of these N2 to N6 Schmitt trigger NOT gate inverters is applied to the base of Q1 transistor 2N2222 through resistor R1.

This part works with a timing setup that includes a capacitor C1 and a potentiometer VR1.

The diodes D2 and D3 are also important because they help adjust how long the charge and discharge take, which affects the duty cycle of the output waveform.

You can change the duty cycle of the PWM signal using the potentiometer VR1.

The PWM signal then goes to a transistor Q1 through a resistor R1 which boosts the signal.

In this setup, the transistor acts like a switch controlling the 6V DC motor based on the PWM input.

To protect the circuit from damage caused by back electromotive force EMF, a protection diode D1 1N4007 is placed across the motor.

This circuit runs on a 6V DC power supply making it great for projects that need low power usage.

Formulas with Calculations:

Below are the formulas with calculations for Simple 6V DC Motor Speed Controller Circuit using IC CD 40106:

PWM Frequency Calculation

The frequency of the PWM signal is determined by the resistor VR1 and capacitor C1 values.

f = 1 / (0.693 * (R_charge + R_discharge) * C)

where,

• f is the frequency of the PWM signal in Hertz Hz
• R_charge is the resistance during the charging phase adjusted by VR1 and diodes
• R_discharge is the resistance during the discharging phase
• C is the capacitance in Farads

Example Calculation:

Lets say:

C = 0.1µF = 0.1 × 10⁻⁶ F

R_charge = 50kΩ = 50 × 10³ Ω

R_discharge = 50kΩ = 50 × 10³ Ω

f = 1 / (0.693 * (50 × 10³ + 50 × 10³) * 0.1 × 10⁻⁶)

f = 1 / (0.693 * 100 × 10³ * 0.1 × 10⁻⁶)

f = 1 / (0.693 * 10⁻²)

f = 144.3 Hz

So, the PWM frequency is approximately 144 Hz.

Duty Cycle Calculation:

The duty cycle determines the percentage of time the motor receives power.

D = (R_charge / (R_charge + R_discharge)) × 100%

where,

• D is the duty cycle in percentage
• R_charge is the charging resistance
• R_discharge is the discharging resistance

Example Calculation:

Lets say:

R_charge = 70kΩ = 70 × 10³ Ω

R_discharge = 30kΩ = 30 × 10³ Ω

D = (70 × 10³ / (70 × 10³ + 30 × 10³)) × 100%

D = (70 × 10³ / 100 × 10³) × 100%

D = 0.7 × 100%

D = 70%

So, the duty cycle is 70%, meaning the motor receives power 70% of the time in each cycle.

How to Build:

To build a Simple 6V DC Motor Speed Controller Circuit using IC CD 40106 following steps are required to be followed while connections:

• Gather all the components as mentioned in the above circuit diagram
• Connect pin 1 of IC1 CD40106 of Schmitt trigger NOT gates N1 to center pin of VR1 pot , connect upper leg of VR1 to pin 2 of IC1 NOT gates N1 through diode D2 and lower leg of VR1 connect to pin 2 of IC1 NOT gates N1 through diode D3
• Connect pin 3 of of IC1 CD40106 of NOT gates N2 to pin 2 of Schmitt trigger inverter N1.
• Connect all the outputs of Schmitt trigger NOT gates of N2, N3, N4, N5 and N6 in common
• Connect all the inputs of Schmitt trigger NOT gates of N2, N3, N4, N5 and N6 in common
• Connect capacitor C1 from pin 1 of NOT gates of N1 to GND of the circuit
• Connect the base of transistor Q1 to common outputs of NOT gates N2, N3, N4, N5 and N6 through resistor R1.
• Connect the collector of transistor Q1 to one end of of 6V DC motor and other end of DC motor connect to 6V positive supply.
• Connect a anode of diode D1 between collector of transistor Q1 and 6V DC motor and cathode of D1 connect to positive supply terminals
• Connect a emitter of transistor Q1 to GND of the circuit
• Connect the positive of capacitor C2 to 6V positive supply and negative of capacitor C2 connect to GND.

Conclusion:

This Simple 6V DC Motor Speed Controller Circuit using IC CD 40106 uses PWM technology to easily and effectively control how fast a motor runs by changing the duty cycle of the input signal.

It includes a Schmitt trigger inverter CD 40106, a potentiometer and a transistor switch, which together allow for smooth and accurate motor speed adjustments.

This circuit is affordable works at 6V and is perfect for small DC motors in hobby projects, robotics and automation systems.

References:

Datasheet IC CD40106