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paralleling of solenoid cabinet locks?

Discussion in 'Electronic Basics' started by Jan Wagner, Jan 17, 2006.

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  1. Jan Wagner

    Jan Wagner Guest

    Hi,

    I'm really stumped on this one...

    Can solenoids that are used to open door locks (house..) be wired in
    parallel, when multiple doors should be opened simultaneously?

    The relevant part of the circuit is
    http://users.tkk.fi/~jwagner/electr/tmp/solenoid-ctrl.gif
    where the solenoid(s) are connected to JP1.

    For now, we have two doors to open simultaneously. The solenoid of the
    first has 200kOhm(!) DC resistance, the other 100ohm.

    The solenoids work fine when individually connected to the above
    circuit's output header, but when both are connected to the header at
    the same time then only the 100ohm one latches. Which not only me thinks
    is quite odd... The +24V rail stays quite solid even when the 100ohm
    solenoid is engaged, and the mosfet's Vds then is just around 0.1V.

    So, with my ignorance of the internals of solenoid door locks in
    general, is there perhaps some property there that makes wiring these
    things in parallel not possible?

    thanks,
    - Jan
     
  2. Dan Hollands

    Dan Hollands Guest


    You need to measure the voltage across the pins at JP1 and at the solonoids.
    Based on the above, the probable explaination is that the 100 ohm load is
    causing a drop in voltage below what the other solonoid requires.

    BTW when you measured the 200k did you try reversing the ohmeter leads. 200k
    sounds unreasonable. Maybe there is a diode in series.


    --
    Dan Hollands
    1120 S Creek Dr
    Webster NY 14580
    585-872-2606

    www.QuickScoreRace.com
     
  3. Sjouke Burry

    Sjouke Burry Guest

    In my former workplace,all doors in the corridoors were
    held open with an electromagnet, at quiting time or fire
    alarm the power would go off,and all doors closed.
    So yes ,connect them in parallel,just supply enough
    power.
     
  4. Jan Wagner

    Jan Wagner Guest

    Dan Hollands kirjoitti:
    Ok thanks, I re-checked now with my scopemeter instead of the
    electronics club's DMM, and there was slightly below 5Vpp 100Hz ripple
    on the otherwise steady +24Vdc rail (rail derived from full-wave
    recitified AC) when the solenoids were "on".

    Couldn't speef up the filter capacitor(s) on the board, but after adding
    a 68ohm 10W resistor in series to the paralleled solenoids the ripple
    dropped to ~1Vpp, and the "problem" solenoid started working - reliably,
    even. :)

    Oddly the same solenoids worked fine on a bench top supply even down to
    10Vdc.

    I guess, lesson learned, some door solenoids just don't like high rail
    ripple.
    200k either way, at least with the DMM. Probably its fooled by the
    inductance. Scopemeter says ca 300ohm, bench top supply's Vout/Iout gave
    ~250ohm, which sound more like it.

    Thanks for the help and info both!

    - Jan
     
  5. Watch out how you wire them. If you common the power and return leads you
    may experience odd effects due to voltage drops. Ideally you should run
    separate wires from the power supply to each solenoid. If you don't, use
    larger than designed conductors if possible. Check what the drop out voltage
    is on each solenoid.
     
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