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120VAC Lamp switched by cmos circuitry?

Discussion in 'Electronic Design' started by [email protected], Apr 12, 2007.

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  1. Guest

    Hey guys. I'm a CompE student so my electrical design knowledge
    regretfully doesn't extend far into SAFELY controlling high voltages.
    I have five 120V AC lightbulbs on a lamp and I need to control them
    individually with a computer. I've constructed the lamp, written the
    software, and built the computer interface, but can anyone recommend a
    way to safely control 120V with a 5V DC control line?

    Or can you recommend a fairly inexpensive switch I can buy?
  2. Relays? How much current are you talking about, are these standard bulbs
    (60-100W)? If you need it to be fairly small, then triacs may be the way to
  3. D from BC

    D from BC Guest

    What's wrong with a relay?
    D from BC
  4. DJ Delorie

    DJ Delorie Guest

    cmos -> transistor -> optoisolator (triac driver, zero crossing) ->
    triac or alternistor

    That's what I use. The key is layout - keep low voltage copper away
    from high voltage copper, use larger trace/space for high voltage,
    plan for insulating the high voltage section to protect the user.

    Use an alternistor if you expect inductive loads.
  5. me

    me Guest

    wrote in
    A relay or a solid state relay. I think Radio Shack (cringe) might still
    sell one that can switch up to 3 amps at 125 VAC...
  6. Donald

    Donald Guest

    Solid State Relay.
  7. MooseFET

    MooseFET Guest

    Don't have a "ground plane" going between the two areas.

    Put the low voltage signals on a connector on one end of the PCB.
    Put the high voltage signals on a connector on the far end of the PCB.

    Make sure to pick connectors that can't be partially or fully mated

    In other words assume an idiot is going to work on it. The idiot may
    even be you one sleepy morning or late night.
  8. LVMarc

    LVMarc Guest

    Go Purdue!

    You need two things:

    A relay made for 120 vac and about a 1KW CONTACTOR rating. P$B T92
    seies for this.

    An interface to go from the PIc I/o pin and to drive the Coil part of
    the T92 contatcor relay. We use this in the backend of a wireless prime
    power actuator switch. Link here..

    Contact me for a breadbaord

  9. eh,
    From MOC3010 triac output optocoupler application note:
    Look at page 5 of the PDF for diagram.
    Been in use here for almost 10 years... (at 230V even :)).
    Switching > 10A with it with an additional thyristor.
  10. jasen

    jasen Guest

    mc3020 and a triac, - google for 3020+datasheet

  11. Eugene Rice

    Eugene Rice Guest

    Crydom solid state relays.

    We used them in the 70s and I'll be damned they still make them and
    Digikey has them in stock.

    They start at US$23 -- not sure if that satisfies your cost criterion.

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