Is This Possible and What Relay Do I Need

Discussion in 'General Electronics Chat' started by CTCGunny, Jan 6, 2018.

  1. CTCGunny

    Thread Starter New Member

    Jan 6, 2018
    6
    1
    Hey Folks,

    I'm a NOOB here and am working on a automatic system for my greenhouse design and I need some help. Is this relay in existence, and where can it be found?:

    DPDT-relay.png

    Any help is appreciated.

    Thank you in advance for you assistance in this matter,

    Chris
     
  2. ElectricSpidey

    Member

    Dec 2, 2017
    444
    96
    Yes it will work, and a relay like that is very common.

    Just be sure the contacts have the correct rating for the motor.
     
  3. CTCGunny

    Thread Starter New Member

    Jan 6, 2018
    6
    1
    So someplace like Amazon will have these? What am I looking for?
     
  4. ElectricSpidey

    Member

    Dec 2, 2017
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    96
    Yea, Amazon will have these, but you may want to skip there and use a reliable source like Digi-Key and such.

    A DPDT relay with 120 volts ac coil.

    The size will depend upon the motor size.
     
  5. CTCGunny

    Thread Starter New Member

    Jan 6, 2018
    6
    1
    Thanks for the help and quick reply Spidey, I really appreciate it.
     
  6. CTCGunny

    Thread Starter New Member

    Jan 6, 2018
    6
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    As long as the coil get enough voltage, the other pins really don't care what the voltage is as long as it doesn't exceed specs, right?
     
  7. ElectricSpidey

    Member

    Dec 2, 2017
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    Pretty much.
     
  8. KeepItSimpleStupid

    Distinguished Member

    Mar 4, 2014
    2,873
    505
    it's a loaded question, but a first order answer is true.

    A contact will have AC and DC ratings, but a contactor for a motor usually is rated in horsepower. They also might have a minimum current and a switching current.

    Too bad you don't have 12 VDC available, because 30-40 Amp automotive relays which have a 12 V coil are perfect. Wait...Your batteries are 12 V.

    So, get an automotive relay for the DC motor and switch the 12 V coil with a simple low current 120 V coil relay.
     
  9. Tonyr1084

    Well-Known Member

    Sep 24, 2015
    2,224
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    I shudder when I see someone wanting to run a fan continuously from a battery. And when you change directions you slam the motor with the opposite current. Given the massive draw and the Back Electro Motive Force (BEMF) a 10 amp motor can easily cook a relay designed to handle 40 amps under those conditions.

    Wouldn't it be better to design a set of relays so that you can run the fan one way or the other OR off when the fan is not needed ? ? ? And wouldn't it be a better design if the fan was powered from something other than a battery ? ? ?
     
  10. CTCGunny

    Thread Starter New Member

    Jan 6, 2018
    6
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    Actually, the fan should be replaced by a linear actuator.
     
    GopherT likes this.
  11. GopherT

    AAC Fanatic!

    Nov 23, 2012
    8,025
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    If you lean to run a fan in reverse, you may run into issues unless the fan was designed for two-way ventilation. Some blade designs are very inefficient when run in reverse.
     
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  12. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    Linear Actuator 00000.jpg Do you have any specs. on lin. actuator. Your drawings are OK, relay 12 V coil, DPDT contacts.
    Possible drawing of actuator.
     
  13. CTCGunny

    Thread Starter New Member

    Jan 6, 2018
    6
    1
    Seems as though the "property police" put the kaboshes on the greenhouse. So all of this was for nothing. Thank you to all who took the time to answer.

    Again, thanks for the help,

    Chris
     
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