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Need current sensing relay

Discussion in 'General Electronics' started by Earl Kiosterud, Jun 3, 2008.

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  1. Hi folks,

    I'm looking for a relay I can put in series with a TV set to sense when it's on. The TV
    uses between 175 and 240 Watts, depending mostly on the backlight setting -- it's an LDC
    TV). So the current will be roughly 1.5 to 2 Amps AC. The contacts need to handle 1/2 A at
    120 Volts AC. I know I could wire up something solid state, with a series resistor and some
    circuitry driving a triac, but I'm looking for something simple and quick. Any ideas?

  2. Eric,

    Thanks. But a relay whose operating current was roughly that of the TV would drop only the
    Voltage it needs. It wouldn't need the diodes and other stuff. I'm hoping. I could still
    add the diodes so that when the TV power was higher (the screen is turned up brighter), it'd
    limit the Voltage across the relay. The relay would need to be just sensitive enough to
    operate with the lower current of the TV.

    Back in the days of turntables, there were boxes into which you plugged your turntable,
    which had a relay whose coil was in series with the turntable. The contacts operated
    another circuit to power other gear when the turntable was running. This would be similar,
    but since there's quite a bit more current available (how much current would a turntable
    draw?), the voltage drop ought to be really low. I guess it's just a matter of getting the
    right coil impedance, given the power the coil needs.

    Hey, lemme ask a similar qestion. Anyone know of a small relay whose coil is easily
    rewindable? I could rewind it with whatever gauge wire would give the optimum results. The
    relay need be a somewhat sensitive one (not big heavy contacts with a big fat spring etc).
  3. neon


    Oct 21, 2006
    when there is current on the TV it means there is the voltage there. and sensing that is much easyer. monitor the voltage then drive a triac or relay to do whatever ,whatfor.
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