A light dimmer is a means of controlling the "brightness" level of an incandescent lamp, in this application we will use a 555 timer to control the brightness level of a low voltage incandescent bulb of up to 60 watts.


Please visit VK2TIP's Book Shelf. My personal recommendations, thanks.

Friday, 29-Jun-2018 03:11:09 PDT


What is a light dimmer?

A light dimmer is a means of controlling the "brightness" level of a lamp, in this application we will use a 555 timer to control the brightness level of a low voltage incandescent bulb of up to 60 watts. Do not confuse that with a fluorescent lamp where it will not work.

How does the 555 timer "light dimmer" work?

The 555 timer "light dimmer" schematic circuit is shown in figure 1 below. For the light dimmer to work the 555 timer is configured as a "variable cycle", astable oscillator running some where around 300 Hz.

This image is copyright © by Ian C. Purdie VK2TIP - 555 timer

Figure 1 - "light dimmer" schematic circuit

The power mosfet used here would be a TO-220 type such as MTP3055E or similar. Note the need for a TO-220 type heat sink for full rated loads.

If you look back at the tutorial on 555 timers (figure 2a - modified duty cycle in astable operation) you will note the need for Ra and Rb. Cunningly this is provided for in our light dimmer circuit by using a 47K potentiometer (often marked 50K).

In our light dimmer circuit, if the potentiometer were set around mid way the Ra and Rb would be something like 25K each. Moving our potentiometer from minimum to maximum varies the values of both Ra and Rb simultaneously and accordingly the duty cycle of the 555 timer controlling our light dimmer circuit.

I am particularly indebted to Philips Components and Semiconductors Australia for their most generous assistance in giving me access to material presented on this page.

Link to this page

NEW! - How to link directly to this page

Want to create a page link to me from your site? It couldn't be easier. No HTML knowledge required; even the technophobes can do it. All you need to do is copy and paste, the following code. All links are greatly appreciated; I sincerely thank you for your support.

Copy and paste the following code for a text link:

<a href="https://www.electronics-tutorials.com/devices/555-light-dimmer.htm" target="_top">visit Ian Purdie VK2TIP's "555 Light Dimmer" Page</a>

and it should appear like this:
visit Ian Purdie VK2TIP's "555 Light Dimmer" Page


Click image to print out a printer friendly version of this page. print

Looking for more? Visit my site map page:

This site is hosted at Press Wizards for better value.

Google Custom Search


Got a question on this topic?

If you are involved in electronics then consider joining our "electronics Questions and Answers" news group to ask your question there as well as sharing your thorny questions and answers. Help out your colleagues!.

The absolute fastest way to get your question answered and yes, I DO read most posts.

This is a mutual help group with a very professional air about it. I've learn't things. It is an excellent learning resource for lurkers as well as active contributors.


555 timer page

555 car tachometer

555 timer data sheet - (120K) in PDF format.

join our "electronics discussion group"

Bibliography: - Philips Semiconductors - Data Handbook IC11

the author Ian C. Purdie, VK2TIP of www.electronics-tutorials.com asserts the moral right to be identified as the author of this web site and all contents herein. Copyright © 2000, all rights reserved. See copying and links. These electronic tutorials are provided for individual private use and the author assumes no liability whatsoever for the application, use, misuse, of any of these projects or electronics tutorials that may result in the direct or indirect damage or loss that comes from these projects or tutorials. All materials are provided for free private and public use.
Commercial use prohibited without prior written permission from www.electronics-tutorials.com.

Copyright © 2001, all rights reserved. URL - https://www.electronics-tutorials.com/devices/555-light-dimmer.htm

Updated 17th May, 2001

Contact VK2TIP