Can't find a 15A rated relay

Discussion in 'General Electronics Chat' started by raisintoe, Nov 17, 2015.

  1. raisintoe

    Thread Starter Member

    Mar 24, 2012
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    I need a relay rated for 15A to 20A at 120VAC with a 12V coil, (Or smaller voltage coil if possible). I am having a hard time finding anything rated more than 10A at 120VAC. I did find this relay on ebay. On the package, it says 20A 125VAC, but when I read the datasheet, it still says that it is 10A at 120VAC under a resistive load.

    How can I find a relay rated at 15A or more, at 120VAC? I have done my searching, and am having a hard time finding any. I need the high current rating in order to run a 1500W heater.
     
  2. raisintoe

    Thread Starter Member

    Mar 24, 2012
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    OK, well I did find this one. It's a pretty beefy little guy.
     
  3. MaxHeadRoom

    Expert

    Jul 18, 2013
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    You need to search using contactor, the Telemecanique range are nice to work with and a replacement coil can be changed to 12vac if neccessary.
    Max.
     
  4. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
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    Or use a Solid State Relay (SSR). Their input is typically a "logic level"
     
  5. raisintoe

    Thread Starter Member

    Mar 24, 2012
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    True . . . actually, I do have some MOC3023 Opto-Isolators and 15A rated Triacs on hand. I should just go ahead and use those. I will need to heat sink my Triac well though.
     
  6. MaxHeadRoom

    Expert

    Jul 18, 2013
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    You need a zero crossing opto drive rather than random phase type.
    These are MOC316X and MOC308X.
    Max.
     
  7. raisintoe

    Thread Starter Member

    Mar 24, 2012
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    And those just prevent surge current? Is that necessary? I have been triggering lamps with these 3023s to purposely start at some point in the AC wave to dim the lights. I do this without the use of inductors
     
  8. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Phase control of lighting or motor is different to controlling an element or heater on/off, which it seems you want.
    Max.
     
  9. raisintoe

    Thread Starter Member

    Mar 24, 2012
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    OK, I didn't know that, thanks. I am planning to turn the whole personal-heater unit on (including the fan), not just the heat element. So it should be the same as if I were to just plug the unit into the wall. I will have to see if there is any circuitry already in the unit itself which protects the heat element from surge current.
     
  10. raisintoe

    Thread Starter Member

    Mar 24, 2012
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    I'd rather not have to order any other parts at this point in my project, so I am going ahead on making a zero-cross detector circuit just with what I have. I have some MOSFETs on hand, but can't understand how to work 'em.

    For a test circuit, I am trying to trigger the P-channel MOSFET to run a current through the 180 ohm resistor. I can not figure out what I am doing wrong. It is supposed to turn on for a small moment (at the zero-crossing moment of the AC phase), then turn back off. Instead, it is doing the opposite, and has a small current, (240uA in this LTSpice simulation).

    Opto with MOSFET.jpg
     
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