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Re: How do you connect a 12V DC solenoid to a 24V DC circuit?

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  • Andrew Mathison (Alice)
    You are correct, always place a reversed diode across any coil that is being switched on and off with DC voltage.....the so called Back E.M.F. can be many
    Message 1 of 35 , Mar 16, 2013
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      You are correct, always place a reversed diode across any coil that is being
      switched on and off with DC voltage.....the so called "Back E.M.F." can be
      many times larger than the original voltage source, that's how a car's
      ignition system makes high voltage for the spark plugs from 12 VDC.

      Regards

      Andy
    • px_charles
      Thanks again for the good advice. I don t think a resistor is needed in this application. When the devices are turned off, the devices will remain off for at
      Message 35 of 35 , Mar 16, 2013
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        Thanks again for the good advice. I don't think a resistor is needed in this application. When the devices are turned off, the devices will remain off for at least three seconds.

        --- In Electronics_101@yahoogroups.com, "Kerim F" <ahumanbeing2000@...> wrote:
        >
        > I like adding a small remark. When I switch a relay 12V (or 24V) coil using a transistor with Vceo > 30V (or 60V) and the relay off response should be `relatively' fast, I add a resistor in series with the reversed diode having a value about the coil's one (or a bit less). In this case, the applied 'transient' voltage at turn off will be about 2*Vcc but the coil energy will also discharge much faster (ratio about Vcc/0.7).
        >
        > --- In Electronics_101@yahoogroups.com, "Andrew Mathison \(Alice\)" <mathison@> wrote:
        > >
        > > You are correct, always place a reversed diode across any coil that is being
        > > switched on and off with DC voltage.....the so called "Back E.M.F." can be
        > > many times larger than the original voltage source, that's how a car's
        > > ignition system makes high voltage for the spark plugs from 12 VDC.
        > >
        > > Regards
        > >
        > > Andy
        > >
        >
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