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LM317 for variable current control?

Discussion in 'Electronic Components' started by Lostgallifreyan, Mar 5, 2007.

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  1. Circuit idea for linear current control from zero amps to fixed maximum.

    |¯¯¯¯¯¯¯¯¯¯¯| R1
    ¡-------| LM317 T |----/\/\/\----x----x------¡
    ¦ |___________| ¦ ¦ ¦
    ¦ ¦ ¦ ¦ ¦
    x !------------¡ ¦ ¦ x
    ¦ VR1 ¦ _¦_C2
    x R2 ¦ D1 D2 ¦ ¯¦¯ x
    ¦ ¡---/\/\/\---x---|<|--|<|---! ¦ ¦
    ¦ ¦ ¦ ¦

    VR1 10K Lin
    R1 1R 2W
    R2 10K
    D1,D2 1N4001
    C2 1000µF Electrolytic

    I don't expect extreme accuracy from this, but could it work ok? Is it a
    disaster waiting to happen? Comments welcome.

    Can I expect to get close to maximum output if the R1 side of VR1 cannot
    fall below 100 ohms, given a high enough R2 side for VR1? And if so, how
    close, and how high might the total resistance for VR1 be allowed to go?
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