LED Lightning

Discussion in 'Equipment' started by denzil, Sep 10, 2012.

  1. denzil

    denzil Webmaster

    How'd you end up driving it? Did you use PWM? I'm not too familiar with all of the capabilities of the RKE. It does look like a great controller but hopefully I can use my Raspberry Pi to build something comparable.

    It's great to hear that quite a few people are using those same kits. I would probably have something fabricated from TAP Plastics to cover those drivers/dimmers. We did the same thing for Brandie's tank for the circuit I built to run four 140mm fans within her canopy to cool off her two 250W MH's.
    Yeah, I was basing my price comparison to the brand name LED lights. For the same price as those cheap Chinese ones, I definitely think a DIY kit would be better. That RapidLED light measures 6" x 9". Not sure if that'll provide enough coverage?
  2. Wow awesome cat anecdotes (sorry to derail the thread, Denzil!)! My wife has been hesitant to get a feline companion because she's afraid the cat will try to jump on the hanging lights or fall into the tanks.
  3. denzil

    denzil Webmaster

    Yeah, my concern was definitely the coverage throughout the tank. I didn't realize you were utilizing two heatsinks so that's probably I'll consider doing. I'll have to do something wider though since my tank is 36 x 18 x 16. I can either do two square 18 x 18 heatsinks or two 36 x 9 heatsinks. I definitely want to make sure I have good coverage. I'll have to look where I can find other heatsink sizes.
  4. denzil

    denzil Webmaster

    Cats learn quick. ;)
  5. If they don't learn quickly they still have eight more lives than we do. :bigsmile:
  6. sfsuphysics

    sfsuphysics Supporting Member

    You could do too of them then :D

    Or don't go with the kit, and simply get a heatsink the size you want. Take a look at this one http://www.ledgroupbuy.com/makersled-designer-heatsink-kit-professional-grade/ very simple to use, you don't need to tap and screws at all. Get the LEDs you want to achieve whatever coloration you desire, and the drivers you need.
  7. denzil

    denzil Webmaster


    Thanks for the link on the heatsink link. I'll definitely have to look into the LED lighting a lot more so I make sure I build exactly what I'm looking for.
  8. xulio

    xulio Supporting Member

    Thanks for the clarification.

    When I looked at the time, it seemed like a lot of work and what you ended up with was something similar to the Chinese LED lights. The ones I got work very well (other than no dimming). That's not to say that I can't hack them later on and add it (in my copious time!).

    I'll look at the kits you mentioned. I'd love to put one of these together.

  9. denzil

    denzil Webmaster

    Hrm, I'm wondering about the orientation of the fans on the heatsinks. I don't remember everything from my Heat Transfer course in college but maybe Mike could help us out here. It seems debatable that the direction of the airflow of the fan should be away or towards the heatsink. However, I was actually thinking what if the fans were set up so that they blow air parallel to the fins of the heatsink. One side would be blowing along the fins and another side would be pulling away from the fins. You'll still be able to achieve the hot air rising while the one side fan pulling cooler air towards the fins. Or maybe I should just have both fans blow air towards each other, still parallel to the fins, since the heatsink I plan on using is probably going to be 30" in length and by the midway point, the airflow from the fans may be negligible.

  10. rygh

    rygh Supporting Member

    My recommendation is still DIY if you can.
    Saves cost compared with fixtures that use quality components.
    Real control over color, spread. PWM control over LEDs.
    Can be built to fit your tank perfectly.
    Fun to build.

    I have been 90% happy with mine. Good growth. Decent color.
    Although if I did it again, I would use all neutral whites, not cool white, and add some violet.

    My fixture is flush with the top of the tank.
    So my "canopy" is only 3 inches high.

    My build thread is here:


  11. xulio

    xulio Supporting Member


    Looks a nice thread for late night reading. I'll check it out. I still got the 120gal that I got from Crabby to set up.

    PS: why did I get back into this hobby! LOL
  12. FeliciaLynn

    FeliciaLynn Supporting Member

    Yeah I'd definitely just get 2 heatsinks and distribute the LEDs on those to make sure you cover the whole tank since its more of a long skinny shape. I get really nice coverage from my 2 15.8"x4.7" heatsinks. As for the fans, I'm honestly not 100% sure how they should be oriented because I've seen them so many different ways. I actually don't even use fans on mine since my fixture is hanging and isn't enclosed. I get really good heat transfer out of the heatsinks without the fans and my fixture just get barely warm to the touch when all the LEDs are running for multiple hours at 100% power. The drivers on my system get a bit warm, but again nothing that has caused an issue. I would definitely recommend the fans though if you decide to go with an enclosed fixture (like in a hood).
  13. denzil

    denzil Webmaster

    Nice, I'll check it out. What do you consider neutral whites? AFAIK from HID's (I know, they're different), 4300K was considered neutral white. Is that about the range you're referring to?
    I totally forgot about the power consumption of the fans that would be needed to cool the heatsinks. I think I'll just stick with the efficiency of the heat dissipation from the heat sinks without the fans. At this point in time I'm thinking of doing a 48 LED build with a 30" x 12" heatsink. That'll leave 6" of tank to surround the heatsink when it's centered. I'll either mount it to goosenecks or in a similar fashion. I'm also going to run the netting across the top of my tank with the screen framing from a hardware store.
  14. sfsuphysics

    sfsuphysics Supporting Member

    Also do note that heatsink is not on the cheap side, I think something like $25 per 6" but you're paying for convenience of sliding in screws&nuts to hold the LEDs to it. You could very well get 20" of black anodized heatsink from a place like rapidled.com for $25 but you need to drill it if you're using screws (you could stick with just thermal epoxy too) and rapidled is actually local, SSF according to their website (they were in oakland) not sure if they allow will-call pickup though
  15. denzil

    denzil Webmaster

    If I wanted it to be ridiculously efficient in dissipating heat, I could get a huge, solid copper heatsink! ;)
  16. magnetar68

    magnetar68 Guest

    The RKE sells a module called an Advanced Light Controller (ALC). It was originally designed for driving a dimmable ballast, not LEDs. It outputs a 0-10V linear signal. In the software, you set the max intensity from 0-100% and specify the ramp time in minutes. Each Port has an A and a B channel that can be separately controlled with it's own 0-10V symbol (i.e., you can set channel A to be a 30 minute ramp to 60% intensity and channel B to be a 15 minute ramp to 75% intensity).

    The issue I had comes from two factors. The first is that the meanwell 0-10V dimmable drivers (not the PWM version since the Digital Aquatics did not have PWM dimmer) sink a lot of current from the control signal (~20mA I think). The second is that the RKE will not supply more than a few mA to the LED controller. Because of this, I needed to build an op-amp circuit in between with it's own power supply that would control 9 LED drivers all sinking some non trivial amount of current from the dimmer control circuit. It was very easy to do as the LM324 does this fine.

    Two other issues of note. The meanwell drivers are not power factored. This is not normally an issue for one driver, but when you get to several of them all turning on at once, they can draw a lot of instantaneous power as their capacitors charge up. This can trip some breakers. I turn mine on in groups of 3.

    The other issue is that the dimming is non-linear. From 0-1 Volt, there is no LED light, then at 1 Volt on the dimmer control, the lights come on at 10%. It is then linear from 1+ to 10V. I hate not having a smoother on. I think most LED dimmable drivers have this behavior, but the meanwell ELN driver definitely do.
  17. sfsuphysics

    sfsuphysics Supporting Member

    Well that would in fact be pretty ridiculous.

    The cost of a solid hunk of copper is not worth it compared to aluminium, besides you want fins too so that you can rapidly dissipate the heat from the heat sink into the environment.
  18. rygh

    rygh Supporting Member

    Specifically, the Luxeon Rebel Neutral white : 4100K typical.
    According to many reviews, those are better than the Cree.

    I have fans, but they are totally overkill. I will probably turn them off some day.
    Regardless, that power consumption is pretty trivial.

    Note that you do need to make sure you have fans if it is totally enclosed, so depends on the canopy.
  19. rygh

    rygh Supporting Member

    I think you mean the meanwell drivers are not inrush limited. Yes, a big issue.
    They do not have active power factor correction either, and that will drive up active current a bit, but that is a different issue.

    I used a high quality 24VDC supply, and RECOM drivers.
    Very efficient. Plus those drivers have both analog and PWM control. But more soldering and work.

    I have PWM controls, and it is still visibly non-linear as the lights are almost out. Not really sure why.
  20. magnetar68

    magnetar68 Guest

    I had read this as the layman explanation from an online forum and repeated the explanation here. I have since read that most PFC LED drivers include inrush limiters in their PFC designs, so maybe that's why the two were combined in the explanation I had read earlier.

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