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Thread: dirk's cheap strange problems.

  1. #11
    Frosty member
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    the key advantage is that they are cheaper for low current applications - that doesn't necessarily follow that they trigger "better".

    it is easy to add some resistance to test it. you don't have to make it fancy to find out if that works. you want some glade for your work room anyway ;-)

    your idea of on board snubber is a good one. I think someone last year soldered them to the underside of the board. no jumper but it worked for him.

  2. #12
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    Mike your glade thought is probably true haha I will see if I can test out some kind of snubber idea (probably just incad set at this point)

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  3. #13
    Workshop Elf dirknerkle's Avatar
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    Quote Originally Posted by jllracer55 View Post
    But I thought one advantage to these chips was the fact that they could be triggered better at Lower current ratings? I am running 70 count LED strands on mine. I dont believe it is a voltage issue, although I have not checked it is more/ merely the fact that they are dimly lit and then once in a while I see a strange flicker out of a set like it is a voltage problem. Makes me think at times that it is the SCISSR that I am using more than anything else and my building method. For those that dont know those are the single channel inline SSR that Dave and Ted designed together for applications like a megatree. Although they were originally designed for cutting a line on a strand I choose not to hack up my good full wave strands and instead salvaged ends off old/ bad incad sets. Guess I am half at a loss to understanding why more current is needed for a chip thats Max current is 1 Amp and I believe output trigger current is quite low compared to say a Triac, although I have not confirmed how low by pulling a data sheet. If this is the case, why dont we design boards with an option to add the snubber resistor and activate it with a jumper rather than having to build a plug for it?

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    The trigger current has nothing to do with the controlling current. The trigger current is set by the chip designer so as to prevent false triggering and as such, they sometimes set it a bit higher so that noise in a circuit or other spurious electrical pulses don't accidentally fire the device. For example, consider the cardiac pacemaker. If they didn't design them with specific, close tolerances and triggering mechanisms it would create some real problems, no?

    And... when designing a board, one makes various assumptions such as "what is the *normal intended use* of this board?" Then you design around that. It's all about tradeoffs. If you want small and cheap you have to minimize parts. If you want lots of options then you allow for multiple combinations of multiple parts, which adds to the overall size, complexity and cost. Neither is right or wrong -- it's just a choice.
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  4. #14
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    Good explanation Dave, thanks! Still though I thought the thinking with going to the VO chips was to eleminate the need for snubbers for it to fire properly. Maybe part of it is my application of the chips? As it seems theres times more of them have a dim glow than others which I guess thinking about it would mean current is leaking through would it not? how is a command to be off going to change this glow if I do plug in an incad set? wouldnt I likely have to fire the channel on and back off in order for it to run with the higher current load and hopefully shut off?)

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  5. #15
    Workshop Elf dirknerkle's Avatar
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    The VO2223A chip was never designed for how we're using it. It's just an optocoupler chip just like the MOC3023 that's popular for triggering TRIACs. Both of them have tiny, low-current TRIACS inside but the difference is that the MOC3023 can handle only about 40ma of current through its TRIAC but the VO2223A can handle upwards of 1 amp. So the VO2223A is like a really beefy MOC3023, and because it has 1A capability, we can use it to actually control lights in a useful way.

    But like any piece of electronics, there are sometimes manufacturing issues that can happen, and static electricity can zap a chip so it leaks current, and sometimes you just get a bad chip. It happens -- after all, the darned things actually do quite a lot for the price.

    But another way LEDs can stay on is by capacitance in the wire. It's possible that enough electrons can accumulate on the wire and on the wire's insulation so that when you cut power to the LEDs, there are still enough electrons hanging around that will keep the LEDs from turning off. This is because the threshold for keeping an LED lit is so incredibly low. The same can't be said for incandescents because the filament-type lights suck up much more current just to emit light at all. Therefore, the problem is sometimes one of finding a way to use-up the extra electrons that are on the wire after the current goes off, and hence the "snubber" idea: adding resistance to the wire so soak up those electrons to a value lower than the LED threshold, and then the LEDs go off.
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  6. #16
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    Quote Originally Posted by dirknerkle View Post
    The VO2223A chip was never designed for how we're using it. It's just an optocoupler chip just like the MOC3023 that's popular for triggering TRIACs. Both of them have tiny, low-current TRIACS inside but the difference is that the MOC3023 can handle only about 40ma of current through its TRIAC but the VO2223A can handle upwards of 1 amp. So the VO2223A is like a really beefy MOC3023, and because it has 1A capability, we can use it to actually control lights in a useful way.

    But like any piece of electronics, there are sometimes manufacturing issues that can happen, and static electricity can zap a chip so it leaks current, and sometimes you just get a bad chip. It happens -- after all, the darned things actually do quite a lot for the price.

    But another way LEDs can stay on is by capacitance in the wire. It's possible that enough electrons can accumulate on the wire and on the wire's insulation so that when you cut power to the LEDs, there are still enough electrons hanging around that will keep the LEDs from turning off. This is because the threshold for keeping an LED lit is so incredibly low. The same can't be said for incandescents because the filament-type lights suck up much more current just to emit light at all. Therefore, the problem is sometimes one of finding a way to use-up the extra electrons that are on the wire after the current goes off, and hence the "snubber" idea: adding resistance to the wire so soak up those electrons to a value lower than the LED threshold, and then the LEDs go off.
    Well I guess maybe I will have to get more resistors and salvage more plugs from somewhere. Crazy LEDs.

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  7. #17
    Rudolph member flashpop's Avatar
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    all my led problems with this glow seem to only happen when things are real wet out side and went away on their own when it dried out. always thought it had to do with dampness in the plugs or on the wires.
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