7.2vdc 4-20mA control

Discussion in 'The Projects Forum' started by raidermanz, Nov 13, 2008.

  1. raidermanz

    Thread Starter Active Member

    Aug 14, 2007
    32
    0
    I am at quite a loss. I am a real novice when it comes to electronics. I learned everything I know by starting with a microcontroller and releasing the smoke from several auxillary components until I stumble upon a circuit which works for what I would like to do. With that background perspective, I humbly ask for assistance on my latest project. I need to control an I/P transducer which operates on a 4-20mA loop. Now, first, I tried to use the PWM in the microcontroller to control the 4-20mA, and I was successful, however, it doesn't work the positioner. This, I am assuming is due to the fact that the positioner data sheet states that the electrical requirement is a 4-20mA loop @ 7.2Vdc. Rats, foiled again!! Will an analog output IC be the easiest way to produce this signal? I was told once that I might be able to use an AD420, but I, as stated before, really don't know much more about electronics other than Ohm's law, and that things don't work once you let the smoke out. Any help would be appreciated.

    Thanks
     
  2. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    Break it down, do you want to translate a 4/20 to a DC voltage (say 0-5V?), or translate a DC voltage to a 4/20 signal?
     
  3. raidermanz

    Thread Starter Active Member

    Aug 14, 2007
    32
    0
    I want to generate a variable 4-20mA signal @ 7.2Vdc, which will be controlled by a PIC microcontroller to set the current signal, and allow me to change the value through a simple pushbutton interface, so I guess, in short, I would like to select a value and have the pic set an output to create the appropriate 7.2Vdc signal strength. I apologize for not have the vocabulary to really explain my system requirements, I hope this works.
     
  4. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    My thought was you might want to translate a variable DC voltage to the current signal. I'm no expert with PICs, and it sounds like you want to do this via the PIC, correct?

    If you want something to translate 0 to 7.2VDC to 4-20ma I can help some, otherwise I'll shutup, watch, and learn.
     
  5. raidermanz

    Thread Starter Active Member

    Aug 14, 2007
    32
    0
    I appreciate the quick response. I want to create a 4-20 adjustable current in a 7.2Vdc circuit. I want to control this using an output from a microcontroller. I think I might be able to do it with a digital potentiometer downstream of the positioner. Does any of this make sense, or do I need to punt?
     
Loading...