Vehicle Detector

Discussion in 'The Projects Forum' started by jack mcleod, Jul 7, 2009.

  1. jack mcleod

    Thread Starter Member

    Sep 4, 2007
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    0
    Placed a 5 ' diam. coil (5 loops) 4-6" under pavement on front road. Object to have the 50 km/hr (31 mph) traffic turn the lights on a xmas tree. Need
    advice about vehicle detectors - what attributes to look for? what to
    avoid? etc.
     
  2. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,173
    397
    The old version traffic detector used the buried coil as part of a tuned circuit oscillator, compared with a standard oscillator. Just speculation: Pass first oscillator thru narrow filter,[ bridged T ] blocking most of the signal. A car passing over would increase inductance lowering frequency, allowing more signal, which then rectified and presented to a V comparator, Walla!! car detected.{maybe].
    Hoe well are you equiped electronically speaking?
     
  3. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,173
    397
    Wild guesses: 80μH , .05μF , about 100kHz.
     
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