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Scrubber build

Discussion in 'Algae Scrubber DIY' started by Tim, Sep 17, 2017.

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  1. LED T

    LED T New Member

    You take this stuff way too seriously.

    Overvoltage to an LED should be common sense. Anytime you add excess current or excess voltage to an LED it shortens the lifespan. The diode breaks down. I could prove this point, but since i feel like this should be common knowledge to someone who deals with LEDs.

    And granted i overlooked the driver information. Sorry. I said i skimmed the information. I thought that was given. But you want to point out what i did wrong. That's ok. I get it, because this is a huge part of your life and your passionate about it. I just don't care.

    The series parallel circuit with a constant current driver that is voltage sensing just seems odd. It through me off. I wouldn't do it, because it's asking for trouble IMO Just because you are trying to cram 10lbs of crap in a 2lb bag. There are many other applications where a series parallel circuit is needed and this didn't seem like one of them.

    With multiple series strands that are in parallel you can destroy many other LEDs compared to shorting out just one or two of one fails. You are taking more of a risk with this set up. But what do i know? I almost took a job offer at Cree in North Carolina several years ago, and I'm qualified for 30-40engineering jobs they have posted in electronic development. So, I don't know anything Turbo.
     
  2. Turbo

    Turbo Does not really look like Johnny Carson Staff Member Site Owner Multiple Units! Customer

    I didn’t mean my response toncome off that way, please accept my apologies

    I was in a hurry, was between basketball games in an all day tournament so I was just getting my thoughts out quickly. In re-reading that I can see how that kinda came off jerk like
     
  3. LED T

    LED T New Member

    It's cool. I'm not upset. I was wrong on some of the things i said, because i posted in a hurry too. I've been working with LEDs specifically for about 10-12 years. And usually I'm not wrong. So, it's my bad too.

    I do accept your apology, and i hope you can accept mine as well.
     
  4. Turbo

    Turbo Does not really look like Johnny Carson Staff Member Site Owner Multiple Units! Customer

    Absolutely, no problem! I tend to worry when a discussion goes sideways - it's always good to have expertise so I was hoping I didn't push you away, I welcome any new information and perspectives, but I have to remember that when I write something technical that it's not in a way that could be taken with a snooty tone...hard to do but I've been guilty of it

    You're right here, it is an odd approach. I searched around quite a bit before I first tried this and I couldn't find a single instance where anyone had tried this method. The reason I wanted to do it was that my original scrubber (Rev 1) had 6x 660nm Reds and one 455nm Blue in a series, with the reds in a rectangle pattern and the blue in the middle, one of these arrays on each side. I made about 30 of these units and it became immediately clear that there was a issue where the growth was zero in the middle and filled in around the edges first, then eventually filled in the middle, but it took a long time. What I realized was that I had uncovered the issue of photosaturation (or photoinhibition, depending on how you look at it) in front of the blues - the intensity was too much. My first solution was to place a small chip of a diffuser in front of each LED, another was to place a very small piece of black electrical on the acrylic panel in front of the LED, both worked OK but that was a work-around.

    That's when I thought about running 2 in parallel to cut down the intensity. The caveat to this working is twofold - 1) they pair of LEDs must be very closely matched (so, from a supplier that properly bins the LEDs) and 2) each LED could run fine if the other one blows and opens it's half of the circuit.

    The goal was really to avoid having to use multiple drivers. Another way to go about it could have been to use 1W Royal Blues, but the development $$ isn't really going into lower-power LEDs, so I nixed that. That was further nixed when I went to violets which are less of a "stable" platform, so I had to go with the best possible LED I could find, and I settled on the 3W SemiLED Hyper-violet. So the technique of the parallel-pair-in-series is not one I use anymore really, but it still works for this specific application.

    Interestingly enough, I have yet to see anyone else even try this, anywhere else. It seems to me that if you wanted to DIY a display tank fixture and throw in some odd colors but have them be very much supplemental, the way to do it and save $$ by not using extra drivers would be to occasionally throw in a parallel pair. If they aren't matched then you might have one drawing more current than the other, especially if they are cheapo grab-bag LEDs.

    Absolutely, and what I've seen done really early in DIY display tank fixture builds (to save $$ because drivers were more expensive and of less variety) was to take multiple "electrically matched" strings (which usually meant using a high power resistor here or there) and put them in parallel & connected to a high-current driver (like 3000mA for 3 strings of Cree RBs) and then put quick-blow fuses on them so that if one LED in a string opened up the circuit, the other fuses would blow and save the other LEDs from getting hit with overcurrent.

    That's not what I had done on my Rev 1 and not what I recommended anyone do, that's something I consider a more advanced technique - the parallel pair within a series doesn't have the same problem because you can take one LED of the pair out and it just gets the normal current vs half-current, it's more of a DIY cost saving measure and very specific I think to algae scrubbers, where the Royal Blues have much more intensity than the Deep Reds at the same current. This is probably why you don't see it being used/recommended anywhere else.

    This is definitely an interesting topic that I really haven't seen discussed much. I'm going to reach out and see what I can find out actually. Rapid LED carries this one AA Battery LED Tester and they say "Safe to use for testing individual LEDs (except for total spectrum UV and arrays)", I thought Steve's carried one but they might not list it. My thought is that "safe" means you're not going to die lol....

    So @LED T back to the OT of the thread (or the recent issue) what do you think might be the problem @Tim had? From what I can see, it looks like he originally was running the red and violets in a simple series chain on a LPC-35-700 driver. This should work like clockwork. Suddenly, the array goes dim like it's not getting the full current to all the LEDs. One the fixture that didn't blow from the 9V test mistake, he took the violet LEDs out of the wiring string and the result was that the reds all fired just fine. This would indicate to me that there was an issue with the violets. The issue seems to be that there was some kind of damage to one or both of them that resulted in at least one of them only being able to "allow" a reduced current to pass through it, in effect, acting as a current choke point of some kind, which of course resulted in all the LEDs experiencing a lower current and thus only lighting dimly.

    I've seen LEDs fry and open-circuit so that nothing fires, and I've seen LED fry and close-circuit so that the rest of the chain still fires, but I haven't seen one cause a current-choke like it appears @Tim saw.
     
  5. LED T

    LED T New Member

    I overlooked the way they were hooked up. I have built about 30-50 DIY fixtures for tanks. I've seen leds dim like this when an individual diode fails. Normally your cheaper UV or Royal blue LEDs. Or if you add a lot of different types of leds on one string. Usually issues with lower binned leds.

    I've also seen it when you hook too many up to the driver. That's why i immediately went to the too many on a string.

    I let my bias get in the way of logic. I shouldn't have in his case. I think he has one or two Uv LEDs that have failed. Maybe it's an intermittent connection that happens internally when the diode heats up(less likely). Or one of the UV leds shorted out drawing too much current overloading the driver to go into protect or a current limiting mode.

    Maybe since he's getting good growth with just the reds i would leave it out all together versus replacing it and having the same issue later.
     
    Turbo likes this.
  6. LED T

    LED T New Member

    And the guys at rapid led will say it's no big deal because of the quality of the leds. But not everybody uses leds from rapid. Or Quality retailers etc. so, the same rule will not apply to all diodes.
     
    Turbo likes this.
  7. Turbo

    Turbo Does not really look like Johnny Carson Staff Member Site Owner Multiple Units! Customer

    He posted a video of it happening on a cold fixture where the LEDs flash brightly a few times then go dim, did you see that one?

    Here it is, it's a few pages back. This is one where he re-wired the 2 violets so they are in parallel and connected to the new driver - which is I believe the LPC-20-700, so this one would have the 30V drop limit vs the 48V limit of the LPC-35-700
    To me there are one of two things going on here:

    1) too much voltage drop, this could be indicated by the quick flashing of the LEDs followed by the dim running, but this doesn't seem quite right to me. However I am not familiar with the over-voltage response on this Meanwell.

    2) both violets have damage so the current path goes through one with short success, then the other, then both, and then they both shut down. Kind of a strange sequence of start-up, but it's just a theory that fits the video.

    That's the first fixture, here is the second. This is all series and I think on an LPC-35-700. In this you can see the closest violet is bright, but the far one is not. I'm not sure if this is a photo effect or what but it does seem like an issue with the violet.

    Also these are SemiLED Violets, so they're not low-end. At least I don't think they are.

    Also worth noting that both of these fixtures were coated in a 2-part silicone to keep them from getting wet.

     
  8. LED T

    LED T New Member

    Let me look at it more. And if you want to talk about the led tester stuff message me. I can explain a little more of why it's important. But don't want to clog up his thread.
     
  9. Tim

    Tim Member

    Please do post everything that may be usefull. I think I also lacked the skills do wire leds properly. Maybe I shortcircuited the leds, as there were quite a few big blobs of solder that may have touched the sides of the ledstar. I studied buds solder skills and will make sure, it will be much better next time. So far the one led fixture I have left is still working. Algae growth decreased a bit. I do still see quite dark green growth.. maybe I should increase the photoperiod from 15 to 18 hours?


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    Verstuurd vanaf mijn SM-G930F met Tapatalk
     
  10. LED T

    LED T New Member

    I still think a single diode or multiple diodes diode are shorted out on each channel. Even after watching the video again. And it's either drawing a lot of current shutting the circuit down (or going into a choke mode like you said). One shorted LED can draw a lot of instantaneous current. The drivers have over current protection, over voltage protection, and reverse polarity protection. The UV leds definitely have an issue with them on both channels. The only way to test them is to take a multimeter and test them with the diode tester. Or test for continuity, or resistance between the anode/cathode.

    Long story short he is getting good results with one side correct with just the reds?

    If this is true then either test the UVs or throw them out. And hook up the other driver to the working leds to verify if it's working or not. See what you can salvage Tim and we can move on from here. Or keep it as is and move on.

    If you need help using a multimeter PM me. I can walk you through the process. Or if you need to purchase one please verify it with me to make sure it has the correct features. It doesn't need to be an expensive multimeter. I think a $6-10 meter will work just fine.
     
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  11. LED T

    LED T New Member

    And my previous reply is only referring to the non working diodes. Not the working fixture.
     
  12. LED T

    LED T New Member

    Let's toss the UVs. Toss the reds that had 9V applied to them. And test the other driver with the working leds
     
  13. Turbo

    Turbo Does not really look like Johnny Carson Staff Member Site Owner Multiple Units! Customer

    Yes, this would be a good idea I think. If you're getting good growth at a given intensity, and you have measureable nutrients and/or are still feeding the same, same livestock, etc - then you can usually extend the hours without any issues. You might even go longer, 20-22 hours/day
     
  14. Turbo

    Turbo Does not really look like Johnny Carson Staff Member Site Owner Multiple Units! Customer

    I'm not quite following this part of your post. I get that when you bench-test a single shorted LED, that's like hooking the 2 terminals of a power supply together, so your instantaneous current is going to be high.

    But, if you have 10 LED in a string and one is shorted, how would you have a high instantaneous current because of that one LED? I'm scraping some rust off my brain from my EE classes 25+ years ago here...and I haven't really thought about this lately from a technical perspective...and I'm not talking about the whole p-n junction level of technical stuff here. I'm just thinking of a more simple answer. Take just 2 LEDs, both working fine, and put them on a power supply (one that works for 1-4 LEDs in this case). Now take the shorted LED and put that in series with the other 2. What has changed? If the 3rd LED is shorted, I would think that would in effect just act like it wasn't there. I must be missing something
     
  15. LED T

    LED T New Member

    I get what you are saying. But have you ever had to test or repair a power supply with a bad bridge rectifier? Or a bad diode in general. The concept is the same. When a bridge rectifier or a rectifier diode fails it will blow a 15A fuse. In large machinery it will blow 80Amp fuses. The short is usually to ground internally because of the catastrophic failure. If the diode is damage or fails under a load it could short to ground internally as well. I Can go on and on about how things fail. But I'm not going to. The instantaneous current i am talking about that shits the driver down is usually a direct short to ground. Do you think a series circuit would put a heavier demand on the power supply if there was an internal short to ground?

    And let's leave out the possibility of connections or wiring touching ground.
     
  16. LED T

    LED T New Member

    Or you can try to understand it as an out of tolerance component that causes the driver to shut down. Plain and simple.
     
  17. Turbo

    Turbo Does not really look like Johnny Carson Staff Member Site Owner Multiple Units! Customer

    Yes, I see how that could do it, but wouldn’t the short to ground in this instance be to the heat sink? Then there would have to be a path back to the driver for the LEDs to continue to operate the way they were in the video.
     
  18. LED T

    LED T New Member

    Look to see if what i am saying is possible by whatever means you feel necessary. Or prove me wrong.

    If you can't understand how a variance in resistance will effect a circuit then maybe we shouldn't be having this conversation.
     
  19. Turbo

    Turbo Does not really look like Johnny Carson Staff Member Site Owner Multiple Units! Customer

    Im not an electronics expert by any means. But I’m an electrical engineer by education so I’m not stupid, but to be quite honest, that’s kind of how you’re treating me here and I don’t get that. I don’t practice circuits and such on a daily basis but I can understand the technical explanation when it’s presented.

    What you seem to be referring to with the high power blowouts is a situation when you have a power source that is higher, like a piece of equipment or controls connected to a 20A or 50A breaker, etc. Now something connected to a circuit like that can experience a much higher instantaneous power before the breaker trips, in the kA range.

    But in the example here, if the driver has not had an internal failure, then the output current is fixed at 700mA, so any kind of short to ground that you’re describing, that’s where I’m not following the explanation.

    If you’re suggesting that the driver indeed is the source of the issue, that’s a different story. I don’t know if @Tim has verified that the issue actually was the driver
     
  20. Turbo

    Turbo Does not really look like Johnny Carson Staff Member Site Owner Multiple Units! Customer

    I’m just trying to figure out the technical explanation for Tim’s problem to try to help him out.

    The reason I changed this forum over from supporting my customers to being open to all algae scrubbers is to help anyone with any issue, without the restrictions of some other forums.

    The forum is meant to be a place where everyone helps each other out, even if it’s not that busy and it’s mostly users of my product...that’s still what it’s here for. So I welcome your help if you’re willing to offer it.

    I don’t always have all the answers, but I’m usually pretty good at finding people who can provide them.
     

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