These are 12-volt DC variable-speed motor controller circuit using CMOS. They use the principle of  PWM motor control mode. We can adjust speed of 12V small motor.

It is easy and uses a few components that IC digital and transistor driver as main.

We have 2 circuits diagram to show you.

First: 4011 PWM motor speed controller

If you want to control the speed of a small 12 volt DC motor. Before will see others circuit. I introduce this circuit as the figure that shows below. They are simple circuit because used a little piece of the component.

There are a Nand gate Digital CMOS IC number CD4011   as main of the circuit. Which it is determined to works in the PWM model(pulse width modulation) so has high It is highly effective, Low power consumption

• We use a potentiometer-VR1 to adjust the speed as needed.
• Next, we use two transistors are TIP41 and BC548 to connect in a Darlington makes drive current higher.
• We should hold a heat sink at TIP41 due to its heat when they are applied.
• While motor function, maybe a reverse current, it must put Diode D1-1N4148 to prevent this circuit.

This circuit we bring to use with AC Line power so has T1 to reduce a voltage down into 12V. Then, AC current flow through to D1-D4 to the full-wave rectifier into DC current. And there is C1 filter to DCV that smooth so well.

Ready to use the 12 volt DC motor controller. But if you want to use it with a 12-volt battery, you can remove this section go out.

Second: Not gate Pulse width modulation motor control

This is the Pulse width modulation motor control using CD40106. Usual, we just enter the voltage and DC current source to the DC motor, Makes motor can be rotated. If will modify or regulate the speed in rotation of the motor.

We will need to enter the voltage look into pulses or periodically. Which will make the average voltage at the output is different. By the pulse voltage is high frequency will have the average voltage than the low-frequency pulse.

The same with the pulse has over duty cycle value, it will have the average pressure much than low duty cycle value.

How is CD40106 Pulse width modulation motor control

The average voltage will be supplied to the DC motor. To control the motor rotation is slow or fast. This circuit uses the above principle. By makes the pulse generator circuit or astable multivibrator Which consists of IC1 / 1 and IC1 / 2 inverter gate with C1, R1, R2, VR1 and diode D1, D2.

The signal generator has the duty cycle value that can adjustable or can rotate with VR1 there.

The pulse signal of the circuit. When is adjusted to get the duty cycle too much there is a maximum of 100%.(signal has the most positive pulse.) Makes the motor it will spin the fastest.

If the percentage of the duty cycle reduced, the speed it will reduce as well. The pulse output signal from IC1/2 will enter to Q1(2N3906), Q2(TIP41) that are connected to the Darlington amplifier circuit. To extend the current pulse up.

Then, drive the motor, connected to the output terminals of the circuit.

The Q2(TIP41) acts through a direct current to the motor. The selection will need to look in accordance with the current use of the motor.

I choose to be more current, because when the motor starts to draw more the current from the power supply than the normal rotation. Or not the motor is loaded.

This circuit is suitable for the DC motor with a power that is not much. Is small enough that the voltage and current not exceeding 12 volts 2 amps.

Which reduces power loss to the motor and the circuits.

The parts list
The resistors 1/4W +-5%
R1 – 330K
R2 – 4.7K
VR1 – Variable resistors 2M
The capacitors
C1 – 0.1uF ceramic type
The semiconductor components
IC1 – CD40106, Hex Schmitt Trigger
Q1 – 2N3906- PNP transistor
Q2 – TIP41- 4A 40V NPN transistor
D1, D2- 0.75 200V Diode, 1N4148
D3- 1A 1000V Diode, 1N4007.

Stops problems about components and The project not work.
Although the circuits are is not the same. It can control speed motor with PWM as well.

But if you want circuit that a good than this circuit. see these circuits.
PWM Control Speed 12V Motor for power dc motor of 12V to 24V motor using TL494.

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