Reduced power relay coil driver

Discussion in 'General Electronics Chat' started by timrobbins, Jun 7, 2010.

  1. timrobbins

    Thread Starter Active Member

    Aug 29, 2009
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    Hi all, I'm just starting to prepare a design for a relay/contactor coil driver which has a reduced power hold state - to save energy loss in a solar powered application. I don't want to use a latching relay due to failsafe reasons.

    I have come across some black box products, such as the coil controllers from Albright - and Kilovac has a good read on their economiser http://www.penninecomponents.co.uk/News/PDFS/Kilovac_Data/economizer_presentation.pdf

    Has anyone attempted to put together a relatively simple driver based on say a 556 and a buck converter. The initial pull in would be a few seconds with the FET on, followed by a level of pwm duty cycle sufficient for acceptable hold in - and possibly an auxiliary contact to reset the timing. The coil would typically be a standard continuous duty coil. Or maybe I need to get a little more exotic.

    Ciao, Tim
     
  2. k7elp60

    Senior Member

    Nov 4, 2008
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    Deleted because information was not revelant on second thought.....guess I'm getting to old for these forums
     
    Last edited: Jun 10, 2010
  3. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    A simple power reducing method is to use a resistor in series with coil to provide proper hold & parall R with a capacitor to provide inrush current to initially pull in relay.
     
  4. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    Thanks for the sermon, kangyuta, but what does it have to do with relays?
     
  5. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    Typically this is called an "economizer" circuit. Googling that term will yield a bunch of circuits to accomplish the task.
     
  6. SgtWookie

    Expert

    Jul 17, 2007
    22,182
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    Google "PWM relay driver" for lots of results.
     
  7. timrobbins

    Thread Starter Active Member

    Aug 29, 2009
    318
    16
    Thanks guys,

    I am going to be using LP339 ic's elesewhere on the pcb, so have just gone through the circuit shown in Kilovac's paper for the CCC and have calculated the component values - not too difficult. I will use a FET instead of darlington, and don't need the rapid turn-off circuit, which simplifies things a bit. Itshould all be quite neat and tidy.

    Ciao, Tim
     
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