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Sizing a power supply

Discussion in 'Misc Electronics' started by [email protected], Apr 28, 2005.

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  1. Guest

    I need to power a water valve actuator with 24AC 650 mA. I cannot
    easily find a 650mA 24VAC supply, but 1amp or 2amp or so I can find.

    Will the actuator adjust to the amperage it needs? Should I step down
    the amperage to 650mA using some sort of current limiting device?

    Sorry for the bsaic question, but I want to buy the right parts.


  2. CWatters

    CWatters Guest

    Either should work fine.

    The current rating of a power supply is usually a maximium rating that the
    load must not exceed. eg the 1A model can supply 24VAC at upto 1A. The load
    only requires 0.65A so it's ok.
  3. tlbs

    tlbs Guest

    Since you need 24 VAC, and not DC, a simple step-down transformer will
    work. You do not need a DC power supply. RadioShack has 25.2 VAC 2
    Amp (Cat # 273-1512) transformer available that will work just fine.
    It's what I use on my sprinkler system at home.

    What CWatters says is true -- the actuator will only draw as much
    current as it needs. You can't "force" 2 Amps down the line (at 24
    Volts or even 25.2 Volts). If the transformer is rated for 2 Amps, all
    that means is that you could power up to 3 actuators simultaneously.

    (PS: I am not a RadioShack salesperson, or associated with RS -- just
    trying to be helpful.)
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