Motor PWM, Ready Kit, 100% Tested


Motor PWM circuit is presented here is based on the readily available timer IC NE555 and regulator  IC 7805. The NE555 is used as timer IC while IC 7805 used as regulator. The speed of motor can be adjusted from 5% to 95%. For minimum value of variable pot the speed of motor is adjusted to 5%. However, when variable pot value is at maximum the speed of motor is adjusted to 95%.

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Application of the circuit:

Most of the timer based circuits available in market use one or another kind of timer IC which increases the cost and also require complicated circuitry around it. But this timer based circuit uses readily available IC NE555 as timer. The functioning of this NE555 based Motor PWM is to adjust the speed of motor from 5% to 95%. Output continuously indicating the variation of variable pot.

Why this particular circuit:

NE555 used here as a timer IC. The variation in output  wanted can be easily done by varying the variable pot using screw driver. The circuit operates normally over a DC voltage of 5V which can be obtained by DC supply source.

Explained working of circuit:

The basic idea behind the circuit operation is to adjust output of the Motor PWM. The NE555  is needed for this purpose. NE555 is timer IC. The output of the circuit is adjusted from 5% to 95% by varying pot. The time during which signal stays high is called ON time. The time during which the signal stays low is called off time. IC 7805 is used as regulator. The output of  IC 7805 is connected to VCC of timer IC NE555.  Pin no. 1 of NE555 is pulled towards ground. When variable pot is at minimum value the speed of motor is adjusted to 5%. Now consider second scenario when variable pot is at maximum value the speed of motor is adjusted to 95%.

How to build:

First of all read the given manual thoroughly and study the circuit given in the figure. Also have look at PCB and components supplied along with the kit. Each component has to be soldered in its position on PCB.

Identification of resistors is done by color coding. The color band on each resistor corresponds to its exact value.

There are different methods in which values are defined on capacitors. But usually values are specified numerically on them.

Can you make out the whole working of circuit and are you able to identify each component separately as to where each of them has to be placed?

If yes only then proceed further to actually mounting and soldering the parts.

Not ICs but their sockets are to be soldered on PCB. This is to make mounting and dismounting of ICs easy while troubleshooting.

Start from left most corner of PCB and solder the components one by one on their correct position on PCB.

Before soldering any component see that you have placed it at its right position and with correct polarity. Give due attention to diodes and electrolytic capacitors as they are polarity dependent.

Do the soldering of other components in the same way while keeping in mind that components with long and sensitive leads like capacitors and transistors are soldered last.

Testing the kit:

After assembling and soldering of components on PCB, connect external DC power source of 5V.

For testing purpose manually vary variable pot using screw driver. Output is adjusted from 5%  to 95% in this case.

Install the unit in room.

ICs used here:

The IC used here is NE555 and IC 7805

These are timer and regulator IC respectively.

The above 8 pin and 3 pin ICs are popular and commonly used IC

Part List


U1                   – NE555

Base                – 8 pin

VR1                – LM7805

Q1                   – IRF450

Resistors(all ¼ watt +/-5% carbon unless stated otherwise)

R1                   – 1k Ohm

R2                   – 1k Ohm

RV1                – 100k Ohm


C1                   – 0.1uF

C2                   – 0.1uF


D1:                  – 1N4007

D2:                  – 1N4007

5 V USB cable