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Electronics finding a relay?

Discussion in 'Modding' started by lizard.boy, 25 Apr 2004.

  1. lizard.boy

    lizard.boy What's a Dremel?

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    well heres the scoop. i want to help make my friend have a really unique xbox so i dreamed up a way to make an ufo effect on the bottem.. with a twist.. real time status ufo lights. aka make it copy the flashing light on the front. i cant find a relay to connect the original status led to a string of 6 or 12 leds in paralel. the leds would be from lsdiodes and i need a relay that would be available from a canadian retailer or with lsdiodes shipping prices :).
     
  2. whypick1

    whypick1 The über-Pick

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    Use an optoisolator. linear described the basic operation here. The only stipulation is that you'll need to find an optoisolator that can run all the LEDs you want. If you're using 3.3v@20mA LEDs with a 12v supply, you should run 3 in series with a 100ohm resistor, and 4 of those in parallel for 12 LEDs total drawing 80mA. To be safe, try to find one that has an max output of ~100mA. I can't think of any that do off the top of my head right now, which means that I don't know how you'd get them in Canada.

    At least it's a start.
     
  3. DanielArdelian

    DanielArdelian What's a Dremel?

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    4N33 optoisolators can supply 150 mA @ 30 VDC. Check the datasheet to be sure. It uses a darlington pair on the output side.
     
  4. cpemma

    cpemma Ecky thump

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    Or add a transistor to a basic optoisolator to boost the current-handling. A 2N2222A will handle over 600mA. The leds & resistors fit in place of load resistor.

    [​IMG]
     
    Last edited: 27 Apr 2004
  5. DanielArdelian

    DanielArdelian What's a Dremel?

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    Looking at the above picture, I dont understand why you need the optoisolator since the circuit you showed uses common grounds on the input and output sides...what am I missing ?
    If so, why not connect the transistor's base directly to the M/B HDD led connector (in series with a 2K2 resistor) ? :eyebrow:


    Note:

    It is also possible that the output from the motherboard uses an open-collector output to drive the HDD led, and then your circuit won't work...

    If that is the case, then the optoisolator's anode should be connected to (+) and the cathode to (-) on the mainboard HDD connector, NOT to the common ground ! :naughty:
     
  6. cpemma

    cpemma Ecky thump

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    It's purely a safety device, to isolate the expensive mobo from homemade & possibly faulty additions.
    You're right, only reason it's drawn that way was to test it worked with the Circuitmaker SPICE simulator. The optoisolator diode is connected in place of the led, no ground connection on the input side. I'll correct it. :blush:
     
  7. lizard.boy

    lizard.boy What's a Dremel?

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    hers what i'm trying to do.
    [​IMG]

    have strings of leds powered off of a molex in the xbox and triggered by the origonal led that goes on and off in the front.

    i forgot to add resistors in that diagram cause i dont know what they would have to be.

    the little squares would be relays/ optoisolators/ i dont know whatelse could work there.
     
  8. SteveyG

    SteveyG Electromodder

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    It is also common practice for some of the motherboard headers to be switched on the negative side. By using an opto-isolator, it doesn't matter how the motherboard manufacturer wired the header up.
     
  9. Dgephri

    Dgephri What's a Dremel?

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    uh, I'm still kind of new to the electronics front, but I used a Crydom DC/DC relay to run my CCFls from my Mobo HDD header, and it works up to 3A.

    Crydom part DMO (the letter, not number) 063 (the number not the letter).

    Control 3-10V (works just fine from mobo header), Load 0-60V, max 3A.

    I hooked up 3 Dual CCCFl inverters just to see how much it would take, and it didn't even get warm after a full defrag (that drive was messy, so an hour or so).

    I wouldn't begin to know how to diagram it, but I just spliced the control into the wiring on the HDD light wires, and the ran 12V into the load pins.

    Currently it runs the 5V load for two UV light cannons on HDD activity, no sweat.
     
  10. SteveyG

    SteveyG Electromodder

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    The trouble with relays for something like this is that they aren't designed to be switched on and off as fast as the HDD light would normally flicker. All you'd hear is a very annoying chattering sound as the contacts go mental.
     
  11. Dgephri

    Dgephri What's a Dremel?

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    True, which is why I picked a solid state relay for my project. No moving parts. Its totally silent. Its about the size of a US quarter and I've never been able to detect any vibration, or heat coming from it, even when holding in my hand.
    [​IMG]
    HDD relay guide
    a guide I did for it a while back...maybe I did something wrong, but after a year or so, I haven't seen any detectable problems with it.

    Just a thought.
     
    Last edited: 28 Apr 2004
  12. DanielArdelian

    DanielArdelian What's a Dremel?

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    Using a SSR (solid state relay) is a really good idea (it could be more expensive than buying individual parts, but it saves a great deal of time and space).

    Actually, a DC-DC SSR contains exactly one input optocoupler and one open collector or open drain transistor output. Usually, industrial SSR's also include some protection circuitry for overvoltage, overloading or driving inductive loads (a diode on the output side), but the basic principle is cpemma's corrected schematic.
     
  13. Dgephri

    Dgephri What's a Dremel?

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    Its a $15 part, but I read about 555 timers, and didn't want to go that far. This does the job, up to 3A, and has 4 solders needed. Plus, if you want to trigger from HDD (3.3V usually), Network (probably off a 5V LED on the board), or any 7V device, you still can use the direct voltage for control.

    Like I said, I'm no electronics guy, I just found a simple part to do what I wanted to do.
     

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