120v.ac to mv/ma

Discussion in 'General Electronics Chat' started by DaveT, Oct 25, 2007.

  1. DaveT

    Thread Starter New Member

    Oct 25, 2007
    1
    0
    Is there a method to obtain a 4-20ma / 1-5mv output from a 120v.ac line?
    I heard somewhere about putting a resisitor in the 120v line?
    Would like to have specifics on this matter.
    Thanks,
    DaveT.
    davetelect.@yahoo.com
     
  2. techroomt

    Senior Member

    May 19, 2004
    198
    1
    first a 4 - 20 ma (1 - 5 vdc) is a conrol signal used to represent an analog value of something, e.g. water pressure, temp, etc.. you can install a resistor, usually 250 ohm to switch back and forth from 4 - 20 ma and 1 - 5 vdc. converting 120 vac power, normally a supply voltage, would do well to power a dc power supply for that control signal system, with more devices to do the controlling. otherwise, no.
     
  3. niftydog

    Active Member

    Jun 13, 2007
    95
    0
    It's recommended that you avoid direct connection to the mains voltage wherever possible. In this case, a simple 5VDC power supply will get you most of the way there. To work out the rest you need to decide whether you need the current loop (4-10mA) OR the control voltage (1-5VDC) to control whatever it is you're controlling.
     
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