Auto Power

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This is a hobby project that most people don't ever need anymore. But there was a time when TVs were old and VCRs were new. This project automatically turns on and off an old (non-remote controlled) TV based on when you turn on and off a VCR (with a remote). This came about because I have more VCRs than I need, and one old mechanical-tuner TV. So, hook the VCR to the TV and now you have a remote channel tuner on an old TV. You can remotely turn the VCR on (of course), and with this circuit it turns on the TV, automatically. Sorry, but there's no remote volume control so you still have to get up once in a while.

NOTE: This project involves working with 120 VAC. This can be lethal to people and electronic equipment. 
Read no further if you're not experienced enough to safely work with this voltage.

If you want to skip the rest of the story, you can go straight to the schematic.

Consider the Alternatives

What else could be done:

Survey the Commercial Market

Ok, I looked a little, but I never found a commercial offering. Then again, I'm not surprised.

Survey the Hobby Market

I couldn't find anything on the hobby market either. Hey, here's a chance to do something new!

The Hobby Project

Remember these old days? Set the mechanical tuner on the TV to channel 3 for the VCR, and now we just need to turn the AC on and off with the VCR. So, how do we detect that the VCR is on? Here's a few ways we know the VCR is on. Can we build a detector?

The winning choice was to detect the signal on the video output. Since this is an old TV, it uses the RF output from the VCR, so the video output jack is available.

How it Works:

The video signal has a well known electronic signature. All we need to do develop a simple envelope detector, filter, comparator, and relay driver. And of course, a small power source to keep things isolated. Take great care that you don't fry yourself, your VCR, or your TV!

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