Solid state relay

Discussion in 'Homework Help' started by E-challenged, Feb 12, 2013.

  1. E-challenged

    Thread Starter New Member

    Jan 4, 2013
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    Is there such a thing? I would like to use an optical switch to turn LED's on and off. My circuit should run between 3-6 VDC and a little over 1 amp. Problem is that this is solar powered and I can't afford a power robbing relay.
    I'm a novice at both electronics and forums. thanks a bunch.
     
  2. WBahn

    Moderator

    Mar 31, 2012
    17,788
    4,807
    Yes. It's called a "solid state relay".

    Google it and see if that is what you have in mind. Come back with any further questions. You might be better off just using a power MOSFET instead.
     
    tshuck likes this.
  3. E-challenged

    Thread Starter New Member

    Jan 4, 2013
    7
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    Thanks for the response. I already goggled Solid state relay and all I found were heavy duty industrial units and one requiring higher voltage. I didn't know what a Mosfet was but after researching this for a few minutes it sounds like the way to go. I'm confused because it seems a Mosfet is the same as a solid state relay or actually is one.

    Thanks again, conrad
     
  4. Brownout

    Well-Known Member

    Jan 10, 2012
    2,375
    998
    If by optical switch, you mean opto-isolator, you can just drive an LED directly from the device. No need for a relay or FET driver.
     
  5. MrChips

    Moderator

    Oct 2, 2009
    12,451
    3,371
    You are confusing a "relay" with a "switch". All you need is a transistor to act as a switch.
     
  6. crutschow

    Expert

    Mar 14, 2008
    13,056
    3,245
    A commercial solid-state relay generally contains an optical isolator at the input which drives either a triac (to control AC) or a MOSFET (to control DC). Thus a MOSFET is only part of one type of solid-state relay.
     
  7. E-challenged

    Thread Starter New Member

    Jan 4, 2013
    7
    0
    Thanks for the help, only problem I have here is as I posted before 'I'm a novice at both electronics and forums'. Currently I have 7 solar powered circuits that run a total of 396 LED's in my gazebo(wish I could show a picture, it's pretty cool because the LED's are just pocking through 1x2 wooden boards). I would like to run all of these on one circuit. I have a solar panel, batteries and I built voltage regulator adjustable between 1.2 - 20 VDC. Now I need to build a watchmacallit that turns it on at dusk and off at dawn. I think I can build that little unit except it will only be capable for 200 Ma. I need it to be capable of 1.2 amps. Therefore the relay. Should I forget about this and return to my other hobbies?
    Thanks again.
     
  8. Brownout

    Well-Known Member

    Jan 10, 2012
    2,375
    998
    A small mechanical relay would suffice for your project. A Raido Shack special will do. Drive it with a small low side transistor 'switch' such as a 2n3904 or a small MOSFET. This is really very simple, no need to give up on it.
     
  9. E-challenged

    Thread Starter New Member

    Jan 4, 2013
    7
    0
    found a 3VDC relay with a current draw of 27Ma(was hoping for zero). I really did want to run this string with 3 volts. So all is good. ;)
     
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