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Light Operated Relay Circuit

Last Updated on September 22, 2021 by Admin 1 Comment

In this post you will learn about a very simple light activated relay circuit in which a relay is toggled On/OFF in response to the light or darkness using a photo sensitive device. The circuit utilizes only a Darlington transistor for activating the relay

The light sensitive relay circuit presented here has been configured such that it increases the sensitivity of an attached transistor many folds.

How the Circuit Works

A couple of transistors can be identified connected in Darlington configuration and the relay can be any type rated between 12V to 6V supply.

The diagram also depicts a photo sensitive device TIL78 but one may practically incorporate any similar phototransistor to serve the purpose, even a stripped 2N3055 power transistor having its junction exposed to light will work.

To do this take a good 2N3055 transistor and very carefully grind of the cap surface such that the internal junction gets exposed. But make sure you do not damage the entire cap or the junction while scraping the device.

The 2M2 preset may be appropriately adjusted for increasing or decreasing the light sensitivity of the photo transistor device

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About Admin

Hey friends, Thanks a bunch for stopping by this site! I am an engineer with a Bachelor of Engineering in Electronics and Telecommunication. One of my passions is gathering information from all sorts of electronics books and tutorials. I then take that information and compile it into a language that is super easy to understand. My goal is to make those complex electronics circuit concepts and technical terms much more accessible for all the new and budding electronics engineers out there. I can also design customized circuit diagrams as required by the users.
If you have any questions related to this field, please do not hesitate to drop a comment! I am always here and ready to help you out with any queries you might have. I cannot wait to hear from you!

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Comments

  1. reyhan says

    April 8, 2025 at 11:19 am

    terima kasih informasinya keren bgt

    Reply

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