Video Activated Relay

Home > Circuits > Other > Video Activated Relay

Author	Views	Views Today	Rank	Comments
	128,898	18		8

This simple circuit from the May 1996 Think Tank column of Popular Electronics activates a relay when it senses a composite video signal. This allows you to use the tuner built into your VCR to turn on and off older TVs that are not equipped with a remote. It can also be used to activate surround sound equipment, turn off the room lights, turn on video game consoles, etc. For such a simple circuit, it is very versatile.

Schematic

Parts

Part	Total Qty.	Description	Substitutions
R1, R2	2	10K 1/4 W Resistor
R3	1	1K 1/4 W Resistor
R4	1	33K 1/4 W Resistor
C1	1	1uF Electrolytic Capacitor
Q1, Q2, Q3	3	2N2222 NPN Transistor	2N3904 NPN Transistor
D1, D2, D3	4	1N4148 Diode
K1	1	9V Relay
J1	1	RCA Jack
MISC	1	Case, wire, board

Notes

Since you may be using this circuit to switch mains voltage, it should be enclosed in a case.

The circuit will also work with most line level audio, although you may have to adjust the value of R1.

Related Circuits

Comments

Add A Comment

Colin Mitchell Faulty Circuit Sunday, November 20, 2011 12:07:28 AM

This circuit will not work. The diode will never remove the voltage on the electro.

anonymous Video Activated Relay Sunday, February 28, 2010 2:01:06 PM

if use this as a voice activated relay what should the value of R1 to be replace. do i use mic instead of rca jack? tnx

alain Video Activated Relay Thursday, January 17, 2008 2:42:02 PM

Simple, efficace, permet de multiples utilisations, par exemple dans la video HF... Merci pour ce petit montage.

anonymous Video Activated Relay Tuesday, January 08, 2008 12:24:17 AM

what is the function of the video activated relay?

adeyinkaq Video Activated Relay Saturday, November 17, 2007 7:35:14 PM

hello,plz i need circuit for my project can you kindly give me comphrensive note about it.

anonymous Video Activated Relay Thursday, May 24, 2007 8:04:36 PM

works great... but you have to use a 2n2222 for Q1... if you use a 2n3904 then you have to replace R1 with a smaller value(51 ohms worked... but it made the video going to the tv get slightly white-washed)... using the 2n2222 saturated the transistor and didnt make the video any different...

ruben Video Activated Relay Wednesday, May 23, 2007 8:14:58 PM

I think the D1 will cause a LOAD on the video signal, and maybe also R1 since it is only 10K.

anonymous Video Activated Relay Saturday, March 03, 2007 6:57:40 PM

This seems like a very good circuit. The only thing I see wrong is that it operates on 9V instead of 12V. Since most of the applications will normally be with a 12V video camera.

The last 10 comments are currently shown. Show All Comments. Add A Comment

If you would like to leave a comment, you can do so using the form below. Comments can be things like suggestions, successes or failures, improvements, similar circuits, error reports, an answer to a previous commenter's question, or anything in between. However if you would like to ask a question it is suggested that you use the forum instead. The forum provides a more robust environment for discussion.

Important: If you post a technical question here, there is no guarantee it will be answered. All technical questions should be posted to the forum. The owner of this site generally does not answer questions in comments.

All comments are subject to approval before they are displayed here, so your comment will not appear immediately. This is done mainly to prevent spam and other abuse. If you wish to remain anonymous, simply enter "anonymous" for your name and/or email.

Name:
Email:
Subject:
Comments:
Anti Spam Code:	Please enter the exact text shown in the image above into the box below. Browser cookies must be enabled to comment on circuits.

Privacy Policy

Colin Mitchell	Faulty Circuit	Sunday, November 20, 2011 12:07:28 AM
This circuit will not work. The diode will never remove the voltage on the electro.
anonymous	Video Activated Relay	Sunday, February 28, 2010 2:01:06 PM
if use this as a voice activated relay what should the value of R1 to be replace. do i use mic instead of rca jack? tnx
alain	Video Activated Relay	Thursday, January 17, 2008 2:42:02 PM
Simple, efficace, permet de multiples utilisations, par exemple dans la video HF... Merci pour ce petit montage.
anonymous	Video Activated Relay	Tuesday, January 08, 2008 12:24:17 AM
what is the function of the video activated relay?
adeyinkaq	Video Activated Relay	Saturday, November 17, 2007 7:35:14 PM
hello,plz i need circuit for my project can you kindly give me comphrensive note about it.
anonymous	Video Activated Relay	Thursday, May 24, 2007 8:04:36 PM
works great... but you have to use a 2n2222 for Q1... if you use a 2n3904 then you have to replace R1 with a smaller value(51 ohms worked... but it made the video going to the tv get slightly white-washed)... using the 2n2222 saturated the transistor and didnt make the video any different...
ruben	Video Activated Relay	Wednesday, May 23, 2007 8:14:58 PM
I think the D1 will cause a LOAD on the video signal, and maybe also R1 since it is only 10K.
anonymous	Video Activated Relay	Saturday, March 03, 2007 6:57:40 PM
This seems like a very good circuit. The only thing I see wrong is that it operates on 9V instead of 12V. Since most of the applications will normally be with a 12V video camera.