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LED indoor bulbs?

Post in 'The Green Room' started by pybyr, Jan 19, 2011.

  1. dougstove

    dougstove Member

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    I use LED sources in the lab and progress is very fast on performance and price.
    Regarding grow lights: There is the potential for a high-efficiency grow light using LED because LED can be pulsed on and off rapidly. Theoretically, and based upon experiments, you can drive maximal photosynthesis with a series of short pulses separated by dark periods, lowering overall electrical input for an LED that can be rapidly switched.
    We do this in the lab for research purposes, but real-world performance is getting close.

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  2. nate379

    nate379 Guest

    I bought one for my front porch light and it was horrible. I have a reg 40w bulb in there, CFLs didn't last very long (cold? auto on??). The LED bulb was much too dim. Perhaps as an accent light under kitchen cabinets it would be ok.
    The rest of my house has either CFLs or T8 bulbs. I installed them all about 3.5 years ago, so far have only had to replace one bulb.
  3. begreen

    begreen Mooderator Staff Member

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    For equivalent lighting, it's important to match the lumens output if replacing with a CFL or LED.
  4. Seasoned Oak

    Seasoned Oak Minister of Fire

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    These things are great Iv got some big flashlights already that consume only 1 watt,and looking for a big campground light as there is no power there now. Been using them in the house when i find reasonable priced ones usually at sams club.
  5. Highbeam

    Highbeam Minister of Fire

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    Just this weekend I had to buy 90 watt halogen par38 bulbs for my new motion light on the barn. It killed me to be using incandescent technology but the CFLs take too long to warm up to even a low glow and the LEDs are super expensive. The 90 watt PAR38s were only 3.50$ each and are on a 5 minute on cycle.

    If the tech was there, these new bulbs would have been LED.
  6. begreen

    begreen Mooderator Staff Member

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    I hear you. There are nice LED commercial floods, but they are costly. For the brief time your spots are on, halogen is fine. 90 watt halogens put out a lot of light.
  7. pybyr

    pybyr Minister of Fire

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    Please tell me more about how this could be implemented [in terms that a technically interested nerdy layperson can understand and maybe DIY with]. I've long had an interest in trying to do some indoor growing (vegetables only) and even lucked into a big halide growlight that was being sold off by the gov't as surplus evidence following confiscation from someone who was growing something other than vegetables, but the realization of what lots of watts X lots of hours would do to my electric bill has always been a show-stopper.

    PS, as long as it does not involve needing to play disco music for the plants to match the stroboscopic aesthetics!
  8. Delta-T

    Delta-T Minister of Fire

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    I wouldn't attempt to grow any serious vegetables with indoor lighting, that said, it is a great way to overcome short growing seasons or overlapping growing season into/out of winter. Plants (generally) know when to flower based on the number of dark hours they experience. Using LEDs or any light for that matter to break up the successive dark hours will trick the plants into continuing to "grow" rather than flower whenever the total dark hours would normally tell the plants to do so. A useful, if not necessary, tactic if you like to start plants early (like late winter) when dark hours are still greater than light hours. A lot of this really depends on the plants themselves. Some plants that originate in the equatorial areas can begin flowering when they have 8-10 hours of dark, where a lot of the plants that originate in the northern or southern extremes will require more dark hours (sometimes 14-16 hours) to know to flower. Beyond tricking the plants I don't think any bulb will ever really create enough photons to replace or come close to equaling the sun. People who choose to grow entirely under artificial lights do so because the y have few options, or are being sneaky.
  9. dougstove

    dougstove Member

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    " Beyond tricking the plants I don't think any bulb will ever really create enough photons to replace or come close to equaling the sun."

    I have pulsed LED systems in my lab that deliver light 90X as bright as the sun, with only a low total power draw.

    pybyr: There was research in the Netherlands ~10 years ago using pulsed red light in green houses, and related work continues.
    There are two key issues:
    i) Green plants absorb light across the visible light spectrum and can use it for photosynthesis. Red photons, though, only carry ~1/2 as much energy as Blue photons, but green plants derive equivalent amounts of photosynthesis from red or blue photons; the extra energy in the blue (or green or yellow) photons is lost, compared to the lower energy red photons.
    So a system that only delivers red photons can in principle deliver more photons per unit energy input, because the energy per photon is lower, But for photosynthesis the red photons are just as good as blue photons (in fact, for complicated reasons, red photons are even better than blue photons).

    ii) Sunlight is continuous, but the photosynthetic system has a turnover time; once it has captured the energy of a photon, it takes about 1 ms to cycle back to a state ready to accept another photon. During full sunlight most crops are light saturated, not using all the light they receive. So, in principle, and in fact, a series of short light pulses spaced out by dark periods can drive over all photosynthesis as fast as continuous light. With LED, pulsed systems are practical.

    I have a set up in my lab that delivers 15 us long pulses of red light, separated by 50,000 us dark intervals; a brief, bright flash every 50 ms. So most of the time the sample is in the dark, doing its biochemistry. Once it is ready, we deliver another flash. For optimal production we would increase the flash rate to about 15 us delivered every 1000 us; a flash every ms; even then the sample is in the dark 98.5% of the time.

    This is not science fiction, the LED we use are nothing very special. The switching electronics are bit more sophisticated, but only because for research purposes we need tight control.
    Now I better get back to work...
  10. sesmith

    sesmith Member

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    4 cree can light replacement inserts in my kitchen. Work great and are dimmable. Also don't act like an open chimney in the light as the units are solid. Several strings of Chrismas tree lights. Also worked good. No individual bulbs out , for a change and only drew 24 watts for 3 or 4 strings. LED bulbs on the mast and interior lamps in my sailboat. Made a huge difference in battery life.

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