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Re: Current Draw Activated Switch

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  • Declan Moriarty
    On Sun, Aug 31, 2003 at 08:19:22PM -0800, Joe enlightened us thusly ... Just lurking on this thread, I ll throw one more approach. Televisions use ~200W on,
    Message 1 of 9 , Sep 1, 2003
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      On Sun, Aug 31, 2003 at 08:19:22PM -0800, Joe enlightened us thusly
      > At 12:34 PM 8/30/03 -0800, you wrote:
      > > I have not seen them for years. a little line current
      > > all
      > >the time, so this thing would have to distinguish between a fraction
      > >of an amp, and the higher draw when the TV is actually on.
      >
      > Use a step down transformer in reverse. Put the low voltage side
      > (secondary) in series with your load and connect a relay to the high
      > voltage side (primary). Use a transformer that has a LOW voltage
      > output, say 3 volts, and a current rating similar to that of the
      > load that you're monitoring. That should give roughly 3 volts line
      > drop to the load being monitored, that shouldn't affect the load.
      > The relay needs to roughly match the output (primary side). You'll
      > have to play with the ratings and you may need to put a dropping
      > resistor in series with the relay to decrease it's sensitivity. The
      > transformer should have low voltage output when little current is
      > flowing to the load (the load is off). When the load is on and
      > drawing appreciable current then the output voltage will rise and
      > engage the relay.


      Just lurking on this thread, I'll throw one more approach. Televisions
      use ~200W on, but may exceed one amp in inrush currents.

      Drop a few volts - A few diodes in series or cathode to cathode 3V3
      zeners (5W). Across this put 2 optocouplers in antiparallel with a 10
      ohm resistor in series. A Small bleed resistor will make sure the
      optocouplers aren't triggered by the bleed current.

      That's 6 components (2 zeners, 2 optocouplers, 10 Ohms and some bleed
      resistor). The trouble with asking is that you have to think all these
      different ideas through ;-).
      --

      With best Regards,


      Declan Moriarty.
      --
      Author: Declan Moriarty
      INET: tech.genius@...

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    • Syd Levine (AnaLog)
      True, but an interesting exercise. ... To: Multiple recipients of list CHIPDIR-L Sent: Monday, September 01, 2003 5:19 AM ... --
      Message 2 of 9 , Sep 1, 2003
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        True, but an interesting exercise.

        ----- Original Message -----
        To: "Multiple recipients of list CHIPDIR-L" <CHIPDIR-L@...>
        Sent: Monday, September 01, 2003 5:19 AM


        > On Sun, Aug 31, 2003 at 08:19:22PM -0800, Joe enlightened us thusly
        > > At 12:34 PM 8/30/03 -0800, you wrote:
        > > > I have not seen them for years. a little line current
        > > > all
        > > >the time, so this thing would have to distinguish between a fraction
        > > >of an amp, and the higher draw when the TV is actually on.
        > >
        > > Use a step down transformer in reverse. Put the low voltage side
        > > (secondary) in series with your load and connect a relay to the high
        > > voltage side (primary). Use a transformer that has a LOW voltage
        > > output, say 3 volts, and a current rating similar to that of the
        > > load that you're monitoring. That should give roughly 3 volts line
        > > drop to the load being monitored, that shouldn't affect the load.
        > > The relay needs to roughly match the output (primary side). You'll
        > > have to play with the ratings and you may need to put a dropping
        > > resistor in series with the relay to decrease it's sensitivity. The
        > > transformer should have low voltage output when little current is
        > > flowing to the load (the load is off). When the load is on and
        > > drawing appreciable current then the output voltage will rise and
        > > engage the relay.
        >
        >
        > Just lurking on this thread, I'll throw one more approach. Televisions
        > use ~200W on, but may exceed one amp in inrush currents.
        >
        > Drop a few volts - A few diodes in series or cathode to cathode 3V3
        > zeners (5W). Across this put 2 optocouplers in antiparallel with a 10
        > ohm resistor in series. A Small bleed resistor will make sure the
        > optocouplers aren't triggered by the bleed current.
        >
        > That's 6 components (2 zeners, 2 optocouplers, 10 Ohms and some bleed
        > resistor). The trouble with asking is that you have to think all these
        > different ideas through ;-).
        > --
        >
        > With best Regards,
        >
        >
        > Declan Moriarty.
        > --
        > Author: Declan Moriarty
        > INET: tech.genius@...
        >
        > Fat City Network Services -- 858-538-5051 http://www.fatcity.com
        > San Diego, California -- Mailing list and web hosting services
        > ---------------------------------------------------------------------
        > To REMOVE yourself from this mailing list, send an E-Mail message
        > to: ListGuru@... (note EXACT spelling of 'ListGuru') and in
        > the message BODY, include a line containing: UNSUB CHIPDIR-L
        > (or the name of mailing list you want to be removed from). You may
        > also send the HELP command for other information (like subscribing).

        --
        Author: Syd Levine \(AnaLog\)
        INET: AnaLog@...

        Fat City Network Services -- 858-538-5051 http://www.fatcity.com
        San Diego, California -- Mailing list and web hosting services
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