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What happened? Solenoid mystery.

Discussion in 'Electronic Basics' started by Eric R Snow, Mar 21, 2007.

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  1. Eric R Snow

    Eric R Snow Guest

    I have a solenoid actuated air valve that only occasionally is
    operated. It is meant to be operated with 24 volts DC. I plugged in a
    wall wart power supply and the solenoid just chattered. Looking at the
    wall wart I see it's a 12 volt DC unit. Duh. So I grabbed the proper
    24 volt DC wall wart off of the shelf and plugged it into the solenoid
    and the thing worked! This was with the wall wart unplugged from the
    wall. My first thought was that maybe the filter cap in the 24 volt
    power supply had held a charge from a previous use but it has not been
    powered up for at least 4 months. The solenoid valve has the coil as
    the only electrical part. The two wires from the coil connect directly
    to the power socket. The 24 volt wall wart has 4 diodes and one 2200
    uf capacitor connected to the xmfr. The time from disconnecting the 12
    volt wall wart and connecting the 24 volt wall wart was about 5
    minutes. Could the solenoid coil have held a charge that long so that
    when connected to the 24 volt unit the field collapsed like an
    ignition coil and provided enough oomph to draw in the plunger and
    actuate the valve?
  2. contrex

    contrex Guest

    The solenoid coil could not have "held a charge". Inductors don't hold
    charges. The magnetic field is only present when current is flowing
    through the coil. Capacitors can hold charges, though, and I guess the
    one in the 24v supply had enough to actuate the solenoid.
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