I'm trying to design a sensor that will be able to determine the power status of a TV (or other electronic device) possibly using an inductor and the variance of EMI from the device to ultimately trigger an 8Vdc amplifier turn-on. Any ideas?
a current transformer on the live wire of the power lead, a rectifier and comparator which could control a relay
martin
Ask Jim Thompson. We had a thread about that a while ago and he then implemented a sensor that turns on some fans when the TV draws more than x mA.
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I bought it ready-made...
...Jim Thompson
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Note that only ONE of the two wires has to go through a current sensor or clamp on type device.
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agreed
martin
I made one by modifying a GFCI. I can post the schematic in ABSE if you like.
Ed
Please do.
Mike
Posted. Ed
No one has mentioned the simplest solution, which is a relay that operates on 0.3V, 1A AC coil current. Just put the relay coil in series with the TV power lead.
This used to be a common item, but (unless you want to buy a few hundred) it might be hard to find or buy. DigiKey lists AC relay KUEP-11A15-120 which takes 24 mA at 120VAC; if you count the wire turns as you disassemble it, and use 1/40 of that number of turns (of thicker wire) to rewire the coil, you 'll have the rating you need. Then you'll have to figure out how to convince yourself and various national safety agencies that it's safe to connect to the 'mains'.
The AC Line Current Detector circuit described at
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