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Raspberry Pi to linear actuator circuit

Discussion in 'Sensors and Actuators' started by supermitchell2, Feb 10, 2016.

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  1. supermitchell2

    supermitchell2

    8
    0
    Feb 10, 2016
    Hello, I need to get some recommendations on this circuit as it is fairly expensive to build. Will this work? I have reviewed everything and I can't find any problems, but I'm still relatively new to circuitry. The linear actuator will at no time surpass 100% load. Note: The 3.3V pins are Raspberry Pi GPIO pins. They can only supply a maximum of 16mA per pin (which is why I am using
    MOSFETs).
    For convenience I have included links to the part datasheets.

    JW2SN-DC5V: http://www.mouser.com/ds/2/316/jw-catalog-461998.pdf

    2N7000: https://www.fairchildsemi.com/datasheets/2N/2N7000.pdf

    FA-RMS-15-12-X: https://www.firgelliauto.com/products/mini-rod-actuator

    C3M0065090D: http://www.mouser.com/ds/2/90/3m0065090d-838565.pdf

    The circuit schematic is included in the uploaded files. I do not know if this will appear as an attached file or displayed in the thread itself.
     

    Attached Files:

  2. Fish4Fun

    Fish4Fun So long, and Thanks for all the Fish!

    462
    105
    Aug 27, 2013
    Hey supermitchell2!

    Welcome to EP!

    It looks to me like you are using a mosfet to control the coil of a relay and are using another mosfet to control the supply to one side of the same relay contacts (and if your schematic is correct you are attempting to use an N-Channel Mosfet to control the high-side which won't work as drawn...but I have NOT looked at the parts sheets to confirm this).....I have to ask....Why? Why don't you just use an H-Bridge from the get-go? It appears you are attempting to drive a coil of some sort....it really isn't practical to drive a coil above a few hertz with a relay....I should also warn you that driving a relay coil OR any other fairly inductive device from a computer's power supply (if that was your intention) is a really BAD idea..... Prolly be best if you just state what you are trying to accomplish and ask for some suggestions about how to achieve it....

    Fish
     
  3. AnalogKid

    AnalogKid

    2,351
    659
    Jun 10, 2015
    So M2 is actuator power on/off and M1 is direction. As above, you have both FETs connected as source followers. This can work if you can supply a gate voltage that is 5-10V greater than the 5V and 12 V supplies, but you can't. Best to change the arrangement so the FETs are switching their loads to ground. Sources to GND, drains to the PI. One end of the relay coil goes to M1 drain and the other end to +5V. The armature that was going to GND now goes to +12V. The armature that goes to M2 source now goes to its drain. AND, you need to add transient suppression diodes across each FET, anode to the source, cathode to the drain.

    ak
     
    supermitchell2 likes this.
  4. supermitchell2

    supermitchell2

    8
    0
    Feb 10, 2016
    Im not trying to run the coil off the computer's power supply. I am using an external power supply. I am trying to control the linear actuator from the Raspberry Pi 3.3V GPIO signals. I need it be able to switch polarities and turn on and off. The DPDT relay was for the polarity switch and the C3M0065090D MOSFET was to control the power to the linear actuator (To provide an on and off state rather than having it constantly moving in one direction or the other). In simpler terms, I am just trying to make the linear actuator go forwards or backwards on command from the Raspberry Pi.
     
  5. supermitchell2

    supermitchell2

    8
    0
    Feb 10, 2016
    I haven't researched the transient voltage suppression diodes yet, but is this what you meant?
     

    Attached Files:

  6. AnalogKid

    AnalogKid

    2,351
    659
    Jun 10, 2015
    Yup.
     
  7. supermitchell2

    supermitchell2

    8
    0
    Feb 10, 2016
    I went online for a few hours and I selected a few transient voltage suppression diodes to go along with my schematic. I was wondering if anyone would be willing to check for me so I don't accidentally destroy my components. I'm extremely new to circuitry and I can't afford to ruin these parts. I've included the updated schematic and corresponding datasheets below if anyone is willing to help.

    SP1003-01DTG - http://www.mouser.com/ds/2/240/Littelfuse_TVS_Diode_Array_SP1003_Datasheet.pdf-776911.pdf

    ICT-12 - http://www.microsemi.com/existing-parts/parts/51168?catid=685#docs-specs

    JW2SN-DC5V: http://www.mouser.com/ds/2/316/jw-catalog-461998.pdf

    2N7000: https://www.fairchildsemi.com/datasheets/2N/2N7000.pdf

    FA-RMS-15-12-X: https://www.firgelliauto.com/products/mini-rod-actuator

    C3M0065090D: http://www.mouser.com/ds/2/90/3m0065090d-838565.pdf
     

    Attached Files:

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