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Re: LED lighting (was aroid recommendations)

  • Subject: Re: LED lighting (was aroid recommendations)
  • From: Steve Marak <samarak@gizmoworks.com>
  • Date: Fri, 23 Jan 2009 15:25:17 -0600 (CST)

Hi Bonaventure,

PAR is just the acronym for "photosynthetically active radiation", i.e., 
that in the frequency ranges which plants actually use (400-700 nm or so).

Since LEDs are by nature monochromatic (the "white" ones either use 
multiple colors together, or have a phosphor which re-emits broader 
spectrum light), plant growers very quickly hit on the idea of using only 
LEDs which emit near the peak absorption frequencies of the two higher 
plant chlorophylls (430-455 nm in the blue, 640-665 in the red).

It's not clear to me whether that really improves things or not, since my 
understanding was that other pigments present in leaves, acting with 
chlorophyll, tended to spread out the range of frequencies which plants 
could use across that 400-700 nm range. So I bought a PAR meter, even 
though it wasn't cheap and it uses funky non-SI units (microeinsteins, or 
often microeinsteins/meter squared/second) that have to be converted to 
and from *everything*.

I don't know if I've really learned much or not (except that in the end, 
you still have to just try things and see if the plants grow well), but I 
can sling a lot more numbers now when I talk about it!


On Fri, 23 Jan 2009, bonaventure@optonline.net wrote:

> Hi Steve,

> In reply, I do not have a light meter to ascertain the intensity of the 
> light (not sure what PAR means). The 3 plants I put in my small 
> diningroom where I had replaced the standard bulbs in a 3-bulb fixture 
> with the LED spotlights, appear to be doing well (did you get the phone 
> camera photos I had e-mailed to you?). I angled the bulbs together a 
> bit, so they converge on an approx. 3 x 3 foot area at plant level. 
> There is a 12 inch pot of Alocasia 'Lime Zinger' that refused to go 
> dormant after being frost-pruned and brought into the basement, 
> Aristolochia fimbriata that unexpectedly broke dormancy with a cutting 
> of a cool Acanthaceae family vine (I'll find name later), and Miltassia 
> Royal Robe 'Jerry's Pick' that really filled up its 8 inch pot, bloomed 
> nicely, but now shows symptoms of virus in new growths so is being 
> isolated and is expendable for this "experiment". Will let you know more 
> later.

> Bonaventure
> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
> Bonaventure, thanks for posting this. I'm very interested in LED lighting, 
> and though I try to keep up on what's out there I hadn't seen this one. 
> Though these sound expensive, for LED lighting on standard bases that can 
> run directly on wall power it's really quite reasonable.
> Have you actually measured the PAR output from these lights yet? 
> Steve
> On Mon, 12 Jan 2009, bonaventure@optonline.net wrote:
> > I got a good deal with these:
> ...
> > The Par 38 is a super bright light that is powered by 120 high intensity 
> > LED's. LED lights are energy efficient and use extremely low watts. This 
> > will result in money saved by lowered utility costs. The lifespan of 
> > this bulb can reach up to 100,000 hours. This bulb emits no UV radiation 
> > and will remain cool to the touch. The voltage of this light is 
> > 110/220/24, uses 8 watts of power and has a standard E27 base. LED 
> > lights

-- Steve Marak
-- samarak@gizmoworks.com
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