Switching 220V ac

Discussion in 'The Projects Forum' started by Konstabel, Jan 31, 2008.

  1. Konstabel

    Thread Starter Active Member

    Jan 31, 2008
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    If I would like to switch a kettle element on and of using small signal electronics, would it be better to do the actual switching using a relay or a circuit using an optocoupler?
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Optocouplers can't handle that kind of voltage or current. They can provide turn on/off signal levels to solid state relays (SSR's), though.
     
  3. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
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    If this is a one-off, the most economic solution would be a relay.
     
  4. Konstabel

    Thread Starter Active Member

    Jan 31, 2008
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    0
    Hi!

    My question yesterday was not completely put.

    I meant to ask: If I would like to switch a 220Vac load, what would be better? A solid state relay or a optocoupler/triac combination?
     
  5. studiot

    AAC Fanatic!

    Nov 9, 2007
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    If you want to switch on and leave on use a relay, solid state or mechanical.
    If you want power control, switching on and off every cycle (or part cycle) use a triac.
    The optocoupler can also be used with a relay.
     
  6. h.d

    Active Member

    Oct 22, 2007
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    triac is faster than relay in switching
    and have lonfer life time
    when you use relay you need optocoupler becuase its through the current in the two sides.
     
  7. studiot

    AAC Fanatic!

    Nov 9, 2007
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    Triacs are not faster than solid state relays (some modules use a triac!)

    Proper mains relays are fully isolated between activator and contacts and need no opto isolator, though one can be used.

    Any form of solid state switching is vulnerable to its environment, which is why the manufacturers of my boiler for instance use relays in the control electronics in the cabinet. It just gets too hot in there.

    But this is away from the point. If you use a triac you have to employ circuitry to switch it on every cycle. This generates RFI problems that need dealing with. So if you just want to use a small low voltage, safe current to switch on/off a large one every now and then and/or have a hostile environment use a mechanical relay. If you want to switch on and off at higher frequency use a solid state device. If you want to switch on and off for power comntrol reasons use a triac plus all the attendant RFI suppression circuitry.
     
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