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Thread: 595 Driving Individual LEDs

  1. #11
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    Default Re: 595 Driving Individual LEDs

    Forgive me if I keep asking questions, but you have alot of info in your head and you keep leading me to more questions. You say to test it with 12v power. I will probably be using the 5v from the pc power supply. Should I be providing 12v instead.

    I'm just having fun with the boards and electricity. I'm just a computer guy, so this is still sort of new to me.

  2. #12
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    Default Re: 595 Driving Individual LEDs

    Quote Originally Posted by slug View Post
    Forgive me if I keep asking questions, but you have alot of info in your head and you keep leading me to more questions. You say to test it with 12v power. I will probably be using the 5v from the pc power supply. Should I be providing 12v instead.

    I'm just having fun with the boards and electricity. I'm just a computer guy, so this is still sort of new to me.
    Sorry for cluttering up your brain with stuff. I have to do that because I no longer have a brain, so now I get to mess with everybody else!!! My brain left me when I got hooked on this hobby and the same will probably happen to you after a while. (The comment usually comes to you in the form of a spouse or other loved one after you brought home another couple hundred boxes of lights, "HAVE YOU LOST YOUR MIND?")

    The 595 uses 5v. It has an additional power connector that allows pumping higher voltage and/or current (within reason) out to the individual circuits themselves for things such as driving LED strings directly. That power goes out through the ULN2803's which can handle up to about 30 volts (if memory serves me right...)

    A great source of quite clean and very steady power is from a disk drive connector inside your PC. There are two black wires, a red one and a yellow one on that connector. Both blacks are ground. The red carries +5vdc, the yellow carries +12vdc. Either can also supply (usually) up to around 2amps of current, too so they're terrific sources for LED control. The voltages are usually rock-solid steady which is also nice. Many DIY'ers just take the power supply out of an old PC and use it to power things -- they make terrific bench power supplies if you ever need one.

    IMO, I try to stick with 5vdc since so many chips and circuits are comfortable with that. You can usually use 1/4watt and often 1/8 watt resistors as well. But 5vdc isn't a trivial amount of power -- especially when you consider that it can be 1-2 amps of current, too. You can easily put up to 24vdc through the small CAT5 wires, for example, but even at 5volts, if those wires get shorted, it can cause a fire so it's nothing to take lightly.

    A normal SSR circuit usually shows that the current limiting resistor leading to the MOC3023 on the SSR is usually 1/4watt and 680 ohms. That's a really good guideline for most small electronic components, including LEDs. You can take virtually any common indicator LED and connect it to 5v power in series with a 680 ohm resistor and it'll be plenty bright and won't burn out. You can generally use a 330 ohm resistor too, with the same safety margin although the LED will be noticeably brighter. You could try 100 ohm resistor and it'd be brighter still.. but... you'll likely find that the LED will start to get hot and heat kills those things (and after a while, it will likely burn out -- and boy, do they stink!!!)

    If you connect your 595 to the 5v output from a PC's disk drive connector, you should have plenty of amperage available to drive not only the 64 LEDs on the 595 board itself, but another 64 individual LEDs out in the field. Most of those white high-power LEDs are designed for about 3.2-3.7 volts, but you may discover that at 5vdc, you may not even need a resistor at all or at the very most, maybe 10 ohms! But I'd suggest trying the 330 ohm resistors for a white LED anyway just to see what you get. I'm pretty sure it won't burn out. Then try two 330 ohm resistors in parallel with one another, which will essentially give you about 165 ohms total resistance. See what happens. If that works, try a 100 ohm resistor. Each step down you'll notice it'll be just a little brighter. Eventually, you'll get to a point where it'll likely burn out and that's part of the fun of experimentation.

    To be sure, there are calculations you can use, but they're predicated on knowing exactly the specs of the LEDs, and the cheap stuff we buy off eBay or other places could easily be factory seconds and have a much wider manufacturing tolerance. So while the calculations are helpful, they provide a decent starting place for further experimentation. Worse yet, out of a dozen of the cheap LEDs there could be quite a wide variance in the amount of current they can take. Hence, you may find some experimentation may be required, which almost always eventually ruins the component you're testing.

    Another thing, don't forget that the cable runs from the 595 to the LEDs will also soak up a little juice -- the longer the cable, the less juice will arrive at the other end. Won't make a lot of difference for a run of less than 50 feet, but you get up to 100, 150 feet and it can be noticeable.

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  3. #13
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    Default Re: 595 Driving Individual LEDs

    Just to add a little to the last post regarding the PC Power supply, to get the newer Power supplies to run with no mother board present just jump the Green wire to any Black on the mother board connector.
    I put a switch in mine for ease of use.
    I thought a 595 for a mega tree was overkill but for a star????? Good on ya
    And dont worry about the comments from family and friends regarding your new mental illness, we understand you.
    Hope this helps and bast of luck.

    Josh

  4. #14
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    Default Re: 595 Driving Individual LEDs

    Quote Originally Posted by slug View Post
    I'm wanting to make a star with individually controlled LEDs. I want to dedicated one 595 board solely to the star. My question is, what is the best way to do this? Can I run wires to the led indicator sockets on the board to the individual leds, or should I run cat5 to the star and keep the board inside? I bought several of the bullet cat5 adapters. I read somewhere that I can jumper the power from pin 1 to the other 3 wires, so that each pair will be powered, but I just want some confirmation from the experts here.

    Thanks.
    Not that you have much time, but if you have 6 or so 485 drivers and some miscellaneous regulators lying around you could create a signal enhancer that would boost the Data, Clock and latch signals. You would need two prototype boards to pull it all off, but I have heard of people extending their 595 to PC distance by driving the signals to 485 pairs.

    Maybe you could search for 595 extender somewhere in the group here.
    There are 10 types of people in the world. Those that understand binary, those that don't and some who know Gray encoding.

  5. #15
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    Default Re: 595 Driving Individual LEDs

    Due to lack of planning, I doubt if I'm going to get the 595 working very soon. Still need the Ren-C board. Working on it, but it's going to be a little while.

    My question is, can I do the same with a Ren64? Can I drive the LEDs directly off the board? I believe it's sending the 5v on pin 1 to the external SSRs, just like the 595 does. I'm closer on getting the Ren64 up and running.

    Thanks.

  6. #16
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    Default Re: 595 Driving Individual LEDs

    There is also some info at this website, (it is "
    daviddth"“s website, he is a member here on DIYC)
    http://www.lithgowlights.com/2008a.html
    [I]Christmas - Light[/I]

    [COLOR="Red"]2011:[/COLOR]
    [FONT="Courier New"][SIZE="2"]6 x Renard 24 DC (My own design)[/SIZE][/FONT]
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    [COLOR="Red"]100 % led lights[/COLOR]
    Thanks to all there is helping me ;)
    [URL="http://www.pcjulelys.dk"]http://www.pcjulelys.dk[/URL]

  7. #17
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    Default Re: 595 Driving Individual LEDs

    Quote Originally Posted by slug View Post
    Due to lack of planning, I doubt if I'm going to get the 595 working very soon. Still need the Ren-C board. Working on it, but it's going to be a little while.

    My question is, can I do the same with a Ren64? Can I drive the LEDs directly off the board? I believe it's sending the 5v on pin 1 to the external SSRs, just like the 595 does. I'm closer on getting the Ren64 up and running.

    Thanks.
    Not really, because the PICs are only good for a small amount of current (about 6 mA after taking into account the on-board status LEDs). The LEDs are not going to be all that bright, as they are typically driven with 25 mA.
    Phil

  8. #18
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    Default Re: 595 Driving Individual LEDs

    That's what I was looking for. I guess I'll have to bust my behind on the 595.

    Thanks.

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