Controlling Multiple Solenoids by varying voltage

Discussion in 'The Projects Forum' started by ofu71, Aug 5, 2014.

  1. ofu71

    Thread Starter New Member

    Aug 5, 2014
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    I want to control multiple (15 - 20) solenoids by using a common single variable resistor. For example solenoid 1 will energize if control voltage is between 1 and 1.25 volts only. Solenoid 2 will energize if control voltage is between 1.5 and 1.75 volts only, etc. Solenoids will be parallel off a single 12 -24 volt line, control circuitry will be parallel off a single 0 - 12 volt line.
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    You may have a problem with the coil hysteresis, especially DC solenoids.
    And where are you going to obtain solenoids with those characteristics?
    The other way is possibly to use LM311's for each circuit.
    Max.
     
  3. alfacliff

    Well-Known Member

    Dec 13, 2013
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    sounds like the method yaesu uses for band switching to antenna tuner, different voltages for each band.
     
  4. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    I would use an LM3914 set up to 0.25v per comparator, or use a series of separate opamp comparators using an LM324, each set at the respective trigger voltage, use transistors to drive the solenoids.

    Like this battery monitor, as your voltage rises or decreases each op amp switches on/off.
     
  5. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    Looks like a job for a microcontroller with an analog input and an appropriate number of outputs (PICAXE40X2), plus driver chips with the needed number of channels (ULN2803?).
    What's the current requirement for the solenoids?

    Ken
     
  6. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    I'd try the dodgydave approach. Two cascaded LM3914s with 20 pull-up resistors, driving 20 P-channel FETs for high-side switching of the relays.
     
  7. Johann

    Senior Member

    Nov 27, 2006
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    LM 3914 is a winner and should work very well for this project.
     
  8. crutschow

    Expert

    Mar 14, 2008
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    I third the motion. ;)

    Note: Be sure each solenoid has a reverse diode across the coil for transient suppression.
     
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