Solenoid Toggle, invert using mosfet?

Discussion in 'The Projects Forum' started by 89ddt, Apr 12, 2014.

  1. 89ddt

    Thread Starter New Member

    Nov 18, 2013
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    Hi guys, new to the form and looking for some help.

    I am controlling a 24 volt DC solenoid using mosfets. I currently have a working circuit, but i need some help learning how to invert the signal to a mosfet.

    What im trying to do is: When a solenoid turns off, the other will turn on as a result until the first solenoid is turned on again.

    The mosfet i am currently using to switch the solenoid is:
    FQP30N06L. Would like to use a second device like this one to switch and drive the second solenoid.

    I also have a couple of these hanging around:
    IRFB9N65A

    Attached is the schematic image.
    schem.jpg

    Thanks for your help!
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Not quite sure of your set up? If controlling all solenoids from the Micro then it should not be a problem if you use an output for each, but if you want to invert the signal to the Mosfet, use a 2n7000 in between Micro and mosfet.
    BTW, you if you drive a mosfet direct from 5v source, use a logic level gate type.
    Max.
     
  3. 89ddt

    Thread Starter New Member

    Nov 18, 2013
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    0
    All my outputs on the microcontroller are tied up to other solenoids so I can't use that to invert the second solenoid. How would the 2n7000 be hooked up? or is there a way I can trigger the second MOSFET without using that component?
     
  4. MaxHeadRoom

    Expert

    Jul 18, 2013
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    You could use the circuit you have, and then use a 2n7000 fed off the same output into another Mosfet to switch the other coil. IOW, one would be an inversion of the other.
    Max.
     
  5. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    What is the purpose of R2? It makes switching the FET fully on more difficult.
    What is the solenoid resistance?
    What solenoid current do you need?

    If I've understood your request correctly, perhaps something like this will do the trick:
     
    Last edited: Apr 13, 2014
  6. 89ddt

    Thread Starter New Member

    Nov 18, 2013
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    Holding current for the solenoid is about 200mA, so coil resistance should be right around 60 ohms? Yes I agree with you that having R2 in there is unnecessary, error i made drawing up the multi sim to post the schematic on here.

    What is the purpose of R2 in your circuit? is that just dissipating power to attain the correct voltage at the gate? But yes your assumption of what I am trying to do is correct.


    Im not sure using a 2n7000 would work due to the holding current for the solenoid at the output (~200mA) would probably cook it after a few seconds.
     
  7. MaxHeadRoom

    Expert

    Jul 18, 2013
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    I meant use the 2n7000 off of the same output and use as an inverter for input into a second mosfet.
    The limit for the 2n7000 is 200ma, but if use as an inverter, the limit would not be seen.
    Max.
     
  8. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    In conjunction with R3 it limits the gate voltage to keep it within spec. 24V on the gate would be excessive for many FETs.
     
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