SCR or mechanical relay 120V @ 20A

Discussion in 'The Projects Forum' started by Firestorm, Mar 30, 2011.

  1. Firestorm

    Thread Starter Senior Member

    Jan 24, 2005
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    0
    I am wanting to control an AC line (~120V, 20A max) (a normal house outlet).

    I'm trying to figure out whether a mechanical relay or an SCR would be better. A mechanical relay will probably be bigger in size, and require a bigger current to throw(which will affect the current specs of my AC/DC converter). But, an SCR has an average power dissipation of alot more normally(so I've read).

    Is the above correct? Ideally I want to draw little current overtime, so a low power 20A scr would be ideal, but I keep seeing average dissipation of about 0.8W.

    Any advice is much appreciated!
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    What are you wishing to control? Are you aware that an SCR is unipolar? If you need full AC power, you should think of a TRIAC, or perhaps a solid state relay (SSR). Both the TRIAC and SSR will need heat sinking is operated above a level of a couple of amps.
     
  3. Firestorm

    Thread Starter Senior Member

    Jan 24, 2005
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    0
    I'm wanting to control a wall outlet.
    So would you recommend using a TRIAC/SSR heatsinked (thinking size might be a bit of an issue) or a mechanical relay?
     
    Last edited: Mar 30, 2011
  4. beenthere

    Retired Moderator

    Apr 20, 2004
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    An ordinary wall switch will do as much. Is this just on/off?
     
  5. Firestorm

    Thread Starter Senior Member

    Jan 24, 2005
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    Yea, it's being controlled with a microcontroller wirelessly. Sorry, I forgot to mention that earlier.
     
  6. beenthere

    Retired Moderator

    Apr 20, 2004
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    Actually, that makes a difference. You might consider using a relay (I find P & B PRD series relays pretty bulletproof) with an optotriac to control it.
     
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