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Thread: DIY COB LED info

  1. #121

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    nimbulan is right. It's not a problem at all. I have exactly same driver/COB combo, and it works if you make parallel loop.

    Code:
    driver+ ---- COB1 ----- COB3 --- driver -
              \- COB2 -/ \-COB4 -/
    COB1 and 2 in parallel and COB3 and 4 in parallel. And these get connected serially.

    You get the same with the following, but the wiring above is better in case one COB gets disconnected.
    Code:
    driver+ ---- COB1 ----- COB3 --- driver -
              \- COB2 -----COB4 -/
    Each COB gets 700mA, which is a good compromise of initial cost vs efficiency for plant growing with this 72V model.
    Last edited by naoki; 02-18-2018 at 08:15 PM.
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  2. #122
    War. War never changes. Est's Avatar
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    Thanks for the confirmation about just making two loops. I've since had time to give it a go and it all works just fine. I've got my solid state relay wired up so I can control the unit with my arduino. I've got a clock shield coming later this week so I'll be able to accurately program in on/off times. Sure I could use a mechanical timer, but anything worth doing is worth overdoing, right? Ultimately I'd like to add some additional feedback loops for temp/humidity control, but that's a little further down the line!

    Everything still needs to be put into some kind of final position, and I need to run the lights for a few hours to make sure that the thermal paste holds up well. I had previously used up more of my fancy thermal paste than I'd thought, so one of the COBs has a different thermal paste on it. I suspect it'll be fine, but I'd like to be around for the initial cycle.

    Huh, I think it might actually be time to get some plants again!

    Oh and a question: I know that the driver for 1 LED wants a 100kOhm potentiometer (and 50kOhm for two, etc). I'm assuming that since what I'm adjusting voltage with the pot, I should use a 50kOhm one since the voltage drop is equivalent to having two COBs with this setup, right?
    Last edited by Est; 02-26-2018 at 11:52 PM. Reason: remembered my question
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  3. #123

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    I think you have one HLG, controlling 4x CXB3590, right? Then you want to use 100k ohm pot as the dimmer. I think the other values of pots are when you are controlling multiple drivers with a single pot.

    Are you using active cooling (i.e. a CPU heatsink with a fan)? Since you have HLG, you might want to add a thermal switch to the dimmer. I described how I attached them to the dimmer circuit of HLG in parallel to the dimmer pot ("thermal protection" section in this blog post). The other day, I was working on the timer region behind a grow tent, and I didn't notice that I bumped off the AC/DC converter for the CPU fans. While I was watering plants, the light went off, thanks to the thermal protection.

    It's a cheap protection. With non-dimming kind, you can set it up to cut off the DC. It works ok, but using the dimmer circuit to dim is probably more gentle to the driver.
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  4. #124
    nimbulan's Avatar
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    It doesn't matter how many LEDs you have hooked up, the potentiometer operates on the driver itself so the target value won't change.

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