limiting DC current

Discussion in 'General Electronics Chat' started by raidermanz, Aug 16, 2007.

  1. raidermanz

    raidermanz Thread Starter Active Member

    Joined:
    Aug 14, 2007
    Messages:
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    I am new to the electronics world, so please forgive my ignorance, I have a mechanical design background so please respond in "little steps":confused:

    I have a heating element which will be powered by a 24vdc power supply, at this time, I am not sure what max current I will be getting, however for this question, let's assume that I have 2A available to the heater. From this same power supply, I would like to power an assortment of low consumption devices. My heater is such that it pulls as much current as I can provide to it when it is below it's rated temperature, and the current draw reduces proportionately as the temperature of the device climbs. I would like to limit the maximum current to the heater to 1.5A.

    I am probably missing an obvious solution, but please refer to the first sentence of my post.

    Thank you for any and all suggestions
  2. John Luciani

    John Luciani Active Member

    Joined:
    Apr 3, 2007
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    Location:
    Massachusetts
    Take a look at the TI TL431 datasheet. There is a current limiter circuit and a current
    sink circuit. Each circuit consists of a TL431, 2 resistors and q power transistor.
    Either circuit will work in your application. Make sure you calculate the power
    dissipation of the high current resistor and power transistor.

    (* jcl *)
  3. raidermanz

    raidermanz Thread Starter Active Member

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    Aug 14, 2007
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    Thank you very much.
  4. mrmeval

    mrmeval Distinguished Member

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  5. davefromnj

    davefromnj New Member

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    Oct 14, 2008
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    Use a properly rated PTC Thermister in series with the load.
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