PWM Motor Speed Controller Using 555 Timer

Today’s project is about PWM Motor Speed Controller using just a 555 timer IC. It is useful for varying the speed of a low-powered DC motor. There are many circuits on the web that can control DC motors for electronic project purposes. But when it comes to controlling the motor uniformly and smoothly, the PWM motor speed controller is the best option like using AVR, 8051 and Arduino.

We can also build this motor speed controller using just a variable potentiometer in series with the motor. But for two reasons, we can’t do it for project purposes. Firstly, the variable resistance dissipates excessive energy as heat, so too much power will be wasted. Secondly, we cannot use this method for automation projects.

Must Read 555 Timer Projects for School and College Project

What is PWM (Pulse Width Modulation)?

Pulse Width Modulation (PWM) or Pulse Duration Modulation (PDM) is a technique for reducing the average power delivered by an electrical signal. The average value of voltage or current fed to the load is controlled by turning the switch between supply and load on and off at a fast rate. It is basically a square wave in which operates as a switch constantly on and off. It is widely used to control the speed of a DC motor and dimmable light bulb.

How Does PWM Control Motor Speed?

PWM controls the speed by driving the motor with a series of ON/OFF pulses and varying the duty cycle. It depends on the modulator voltage. The higher the voltage, the speed of the motor increases. By keeping the frequency constant, the fraction of time increases when the output voltage is high compared to when it is low.

555 Timer As a PWM Generator

Like microcontrollers, we can also use a 555 timer as a PWM circuit if we design it into astable mode. There is a detailed block diagram and graph of the 555 timers in astable mode. There we can see that the output is “HIGH” when the C1 capacitor is charging through R1 and R2 resistors. While the other part is “LOW” when the C1 capacitor discharge through the R2 resistor.

555 timer block diagram

So we can see that if we change the value of any of the three components, the output value of the whole duty cycle will change. To solve this problem, we need to add a potentiometer instead of just an R2 resistor and add two diodes.

555 timer block diagram replacing with potentiometer

This time “ON Time” will depend on the R1, C1, and the left rotation of the potentiometer while “OFF Time” will depend on only the C1 and right rotation of the potentiometer. Due to the same total resistance during charging and discharging, one cycle of the frequency will also be the same.

Being R1 resistance is so smaller than the potentiometer, the control over the charging and discharging is easy to control. Pin number 5 i.e. control pin of the 555 timer ic is unusable and due to avoid external noise it is connected with a 100nF capacitor. To prevent any output resetting, pin number 4 is used with VCC directly.

The output of the 555 timer ic can only handle 200mA current for load. Due to this reason, we need a MOSFET to drive the motor that exceeds this current rating. I used a MOSFET which is able to handle upto 5A current for this purpose. We need to connect the output with the base of the MOSFET using a 1KΩ resistor. After that, we need a feedback diode parallel to the motor for voltage fluctuations.


pwm motor speed controller
PWM Motor Speed Controller

Circuit Diagram

PWM Motor Speed Controller Circuit Diagram
PWM Motor Speed Controller Circuit Diagram

Components Required

  • 555 Timer IC
  • 1N4007 PN Diode
  • 100nF Ceramic Capacitor (x2)
  • 1KΩ Resistor
  • 100KΩ Potentiometer
  • Motor
  • 9V Battery

PCB Design

For removing messy wiring and giving a clean look, I designed a PCB prototype for this project. It is also helpful for troubleshooting that runs great without any errors. To design this PCB board, I used EasyEDA as it is too easy to use. For ordering PCB for this, I personally prefer PCBWay.

Gerber file for PWM Motor Speed Controller.

PCB View

PWM Motor Speed Controller 2D View
2D View
PWM Motor Speed Controller 3D View
3D View

Order PCB From PCBWay

This project is sponsored by PCBs are required everywhere in the electronics industry. So it needs to be good enough and have to serve the purpose for which they are needed without costing exorbitant amounts. PCBway offers all your needs come true. PCBWay is one of the largest PCB (Printed Circuit Board) manufacturing companies in china. It offers PCB prototype, PCB Assembly, SMD Stencil, and Flexible PCB.

They ship to more than 170 countries worldwide and process more than 2100 PCB orders a day. It feels like PCBWay gives an excellent price and customer service factor in one single serving. I personally ordered PCBs from PCBWay for my projects for just 5 dollars. I’ve used other PCB manufacturers too, but PCBWay has been offering the most reliable and consistent that I have tried. What is also spectacular about PCBWay to me, as a maker and customer, is their service. From their friendly support staff to their intuitive, user-friendly website features, it all counts towards what makes PCBWay an ideal company and brand for any electronics hobbyist.

Standard quality for any product needs to be maintained using some parameters. PCBWay gives that opportunity through quality control in designing and manufacturing. At first, they ensure the accuracy, clarity, and validity of the PCB files that we sent to them.

Then all the boards will go through the most stringent tests other than the basic visual check. They adopt most of the testing and inspecting equipment used in the industry, such as Flying Probe Testers, X-Ray Inspection Machines, and Automated Optical Inspection (AOI) Machines. They are having 50+ new engineers on the daily basis around the world using PCBs for their work, who trust their reliable quality.

Features of PCBWay

PCB Prototyping & Manufacturing: PCBWay produces FR-4 and Aluminum boards and advanced PCBs like Rogers, HDI, and Flexible and Rigid-Flex boards, at a very reasonable price. Just check this Instant Quote to order premium PCBs for your hobby projects.

PCB Assembly: It not only offers PCB Prototyping but also offers PCB Assembly service. You can order a full PCB board with attached components by uploading your file. SMT & THT assembly starts from only 30$ including free stencil and worldwide shipping. The components can be sourced and provided by PCBWay, or by the clients themselves.

Open Source Community: It not only offers PCB Prototype & Assembly services but also gives opportunities to students for sponsorships. I think this is so great. They feature their projects on the website also.

3D Printing & CNC: It also produces Rapid Prototyping like 3D printing, CNC Machining, Sheet Metal Fabrication, and Injection Molding. The quality of the product is too premium and reliable. And also the best part is that you will receive your order within a minimum of 3 days.

Services: PCBWay offers great servicing of its products. It takes only 3 to 15 days according to the courier service to deliver your products. Also, it has a live support facility. Whenever you have any problems, you can always reach a live customer service person to respond to your emails or messages. They have the “Return and Refund” principle, for every unusable board caused by PCBWay, they will rebuild and refund the order soon.

Working Principle of PWM Motor Speed Controller

In this project, a DC motor is operated by a simple 555 timer ic. The 555 in this project is being operated in astable mode, which produces continuous HIGH and LOW pulses to rotate the motor.

Surprisingly, we can use this circuit as an astable multivibrator with low costs and materials. In this mode, the 555 timer ic can be used as a pulse width modulator with a few small adjustments to the circuit. The frequency that is needed for operating the motor is provided by the passive elements i.e. resistances and capacitors attached to it.

2 thoughts on “PWM Motor Speed Controller Using 555 Timer”

  1. No, one terminal is connected to direct positive (DC) or line (AC). another terminal connected to TIP122 for switching the motor On/Off (DC) or to the relay (AC)

Leave a Comment