Sensing an ON condition inductively through a power cord.

Comments

• Leon Posts: 7,620

  2009-07-10 12:49 edited 2009-07-10 12:49

  Hall effect current measuring devices made by Allegro have a copper conduction path just above the die that has to go in-line with the supply. It might be easier to use a current transformer.
  
  Leon
  
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• LoopyByteloose Posts: 12,537

  2009-07-11 08:55 edited 2009-07-11 08:55

  Yeah, I have seen that current induction transformers are a very viable alternative. The truth is that I am abandoning this for now as I would have wire everywhere to monitor current.
  
  In the everyday world, power outlets are distributed about every 3 meters along a wall. That distribution creates a very large barrier to centralized home automation. Unless each outlet were to provide a twist pair that could be fed to a centralized microprocessor for each room, not much could be done.
  
  I'm not ready to rip up baseboard and install wire for this. One day, there may be a commercial market for AC power outlets with built in current sense that feed data for remote monitoring. Someone will make a bundle on it, but not me.
  
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• kwinn Posts: 8,697

  2009-07-11 16:19 edited 2009-07-11 16:19

  You could always build a wireless module that plugs into the wall outlet much like the X10 units do, or use the power lines like X10 does.
• sam_sam_sam Posts: 2,286

  2009-07-11 19:56 edited 2009-07-11 19:56

  Loopy Byteloose
  
  
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  Built your Tweet-A-Watt__You take Xbee adapter kit and a Kill·A Watt Meter······
  
  ·It starts on page 112
  
  IN··· MAKE Magazine··· Click_Here· ·to read more It will only let you read the first three·page of the magazine I can share it with you if you want me to
  
  just PM me with the Email address that you want to use
  
  Here is where you can a kit with all parts need Click_here
  
  I can not share this with every one·· ··ing so sorry· ·I did this one time and I had to have my account reset
  
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  ··Thanks for any··that you may have and all of your time finding them
  
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  Sam
  
  Post Edited (sam_sam_sam) : 7/11/2009 9:46:46 PM GMT
• Prettybird Posts: 269

  2009-07-12 22:26 edited 2009-07-12 22:26

  I use to use a torrad (doughnut shaped coit used in swithching power supplys ) with 1 or 2 loops around it to mesure changes in current for servo motors in CNC machinery. Measured directly with a digital multi meter. You could amplfly the signal with aan op amp and just figure how to calabrate it compairing to a clamp on ampmeter. An inexpensive way to go. You could install one where the pain power comes in (with great caution) and measure the whole house if you want. If you are a beginner I suggest to get an electrician to help. Main power is dangerous. Remember to loop only 1 wire, not both.
• CounterRotatingProps Posts: 1,132

  2009-07-18 22:10 edited 2009-07-18 22:10

  Loopy,
  
  take a look at the COIL_demo.spin in the prop tool's "library" folder - I've done what pretty much what PrettyBird suggested, but even simpler: just wound a bunch of loops around one line of a power cord and op-amped the signal, but, as he mentions, you can't wrap it around the whole cord (I think because it gets phase cancelled, like a twisted pair cable.) All the CT's I've seen go around just one leg of the line. So, right, all you need is a bit of current to tell it's on, right?
  
  - H
  
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• Ugha Posts: 543

  2009-07-20 12:57 edited 2009-07-20 12:57

  Have you thought about using an SX and a cheap wireless module? You can get a wireless
  transmitter/receiver pair for around $15 on some sites. They work pretty good, they lose
  data a sometimes but you make up for this by sending repeated transmissions and a
  checksum.
  
  You could have a monitor on each outlet pretty cheaply.