Lights for starting from seed.

[attml]

I use shop lights from Home Depot. Here are a few shots from when they were in full swing last year.

[ivanaz]

I've searched the forum but couldn't find anything on using LEDs as grow lights. They have come down in price so I am considering adding them to my current modest setup of 2 ft fluorescent tubes (instead of just adding more tubes). I've looked at red and blue 3528 and 5050 LED strips. Does anyone have any experience with LEDs? Any thoughts on LED vs fluorescent? I only plan to use the lights for the first 2.5 months, until I can get the plants outside.

[sio2rocks]

Originally Posted by ivanaz

I've searched the forum but couldn't find anything on using LEDs as grow lights. They have come down in price so I am considering adding them to my current modest setup of 2 ft fluorescent tubes (instead of just adding more tubes). I've looked at red and blue 3528 and 5050 LED strips. Does anyone have any experience with LEDs? Any thoughts on LED vs fluorescent? I only plan to use the lights for the first 2.5 months, until I can get the plants outside.

I would suggest going for additional tubes or adding a few fixtures with CFLs in them. For one LEDs are still expensive for the amount of light required for good growth of seedlings (at least 800-1000 lumens, most that are cheaper are in the range of 600 lumens), and two they typically have a fairly tight light spectrum. They are much less of a full spectrum light source (unless you have multiple rated at different nm ranges and they are close is proximity) than daylight fluorescents.

A four foot 2 lamp fluorescent fixture from HD or Lowe's is $12-13 and two 6500K daylight bulbs are about $5-8. Conversely, one can buy 3 26 Watt CFL daylight bulbs for $10-15 with some really cheap sockets and get almost the same results for less total outlay but have to do some DIY wiring and the such. If you attempt the 2nd option be sure to keep things safe and out of any source of water.

LEDs show some promise for the future but currently for the lumen rating and spectrum requirements of multiple diodes they are much less economical than fluorescents. Especially for the use of seedling starting a few months out of the year. Continuous indoor growing might be another thing entirely.

M2C

Colin

[Hotwired]

The one thing that LED lights offer is directional lighting. The LED lamps use bulbs with a 90 to 120 degree cone, so all of the rated lumen actually strike the plants, where only 45% of the Fluorescent tube's rated lumen actually reach the plant. A 4000 lumen LED provides about the same coverage and intensity as 9000 lumen 4-bulb Fluorescent. Colin is correct that the LED systems have 3-4 narrow band wavelengths. Here's a spectral curve I ran on a UFO-90 LED system. This was the older model system that used only 3 types of diodes. The newer model includes white diodes, but as you can see, it's not very good coverage. The problem is that there is still limited wavelengths available, though that is changing rapidly.



I have several curves run on LED brands and models. I have ordered a LED strip that mounts into a Fluorescent fixture, and will be running those curves soon. Currently there are several good LED systems, but no Great ones.

[Billydove]

Hi everybody

I'm going to try for the first time to start from seed. I have a three foot wide by two foot deep plastic shelving unit with four shelves that i am going to use for holding my seed trays. I'm having a hard time finding 3 foot wide florescent fixtures that are not over $30 a pop and I need four of them for each shelf.

So after reading all the great comments in the thread I think I will make my own light strip using CFL bulbs and light sockets.

No worries, I'm quite handy and my father is a electrician and I will make sure he approves my craftsmanship

Question(s)
How many CFL bulbs per a 3 foot wide shelf should I use? Single Row?

Amazon has Sylvania 29490 23-Watt CFL Mini Twist Light Bulb, Soft White, 6 pack for $15.00. Are these the correct CFL bulbs to get?

http://www.amazon.com/Sylvania-29490...hu-rd_add_1_dp

Thank you for your help

Billy in Northern Virginia

[Hotwired]

You want the 6500K Daylight Bulbs, not the 2700K Warm. The warm are for flowering. Pack the CFL's as tight as possible and build a reflector covering it with aluminum foil.

BTW if it's your first time starting seeds inside, there's a lot of good info on Tomatoville. Here's my method.

A JuryRigger's Guide to Seed Starting

[Doug9345]

Here's what I use for a CFL Fixture.
http://www.tractorsupply.com/jobsmar...r-lamp-3208291

I buy my bulbs from Walmart. 6 packs are in the same price range you quoted. What I like about these fixtures are that they are made to take a 250 watt infrared lamp to keep chicks warm so the sockets are well made. I've had a CFL in one for a year now that I've run 12 hours per day so it doesn't seem to be overheating the CFL. I'm sure you can build something cheaper depending on what sockets you use but these are handy. Right now it's lighting a petunia that I've had for a couple of years.

[Got Worms?]

I use T8s...two banks of two double fixtures. 8 tubes (6500k) for a total of 256w. This covers an area approximately 2' x 4'. (31x51) close enough.

These fixtures were old T12s with magnetic ballasts, but I converted them over to T8 by installing the electronic ballasts and rewiring. It was the cheapest way out two years ago when I did the job. But hey, they're doing fine, giving me more light for less wattage...256w vs. 320w.

I use window chain and pins to adjust them. The enclosure is covered with 1/2" rigid Thermax insulation with reflective Mylar inside. I keep the whole shebang in an unheated room and the plants stay between 62*-70*.

Works well for my needs.
Charlie

[Billydove]

Thank you "Hotwired" for pointing out I was looking at the wrong bulbs. I am also enjoying the link to your setup. Extremly informative!!!

Thank you as well "Doug9345". Tractorsupply site is currently down for maintence however I look forward to seeing what fixture you use. Would you mind telling me which CFL bulbs you get from Wallyworld as I do not see any 6500K Daylight CFL Bulbs on their site.

Very Nice setup "Got Worms?", I wish I had the space for such a setup.

Thank you

[Doug9345]

I just looked up the spec on them as it isn't on the box.
Heres what I bought a while ago.
http://www.bulbtronics.com/Search-Th...ookieSupport=1
17 says 2700K. Maybe not the best, but it grew great tomato plants last year and my Petunia has grow and flowered well. Of course the petunia also gets some outside light so it may balance out.
This is the fixture and petunia. Maybe I'll find some higher color temperature lamps but maybe not because I use the two mostly for things like you see right there.

[Hotwired]

Here are the Spectral Curves for a 6500K daylight CFL, and a 2700K Warm White CFL. I overlaid them onto the PAR Curve or the light requirements of plants. I also labelled the color range for foliage growth and the range for flowering. You can see that the 6500K bulb covers the full spectrum, while the second curve for 2700K is terrible for Foliage Growth.

6500K NATURAL DAYLIGHT CFL



2700K WARM WHITE CFL

[ChrisK]

Can you explain the PAR curve re:what you are showing with those units on your Y axis?

[sio2rocks]

Originally Posted by ChrisK

Can you explain the PAR curve re:what you are showing with those units on your Y axis?

I'll Answer for hotwired since he isn't here right now. The PAR curve is the region of visible light between 400 and 700 nm emitted by our Sun that plants can use for photosynthetic processes. PAR stands Photosynthetically Active Radiation. The curve shows radiation energy in some units on the Y-axis that aren't important for our purposes. On the x-axis in the wavelength of light that those energies occur along the curve. So if we want a light source that is the perfect clone of the light available to plants by the Sun we would want its radiant energy to fall exactly on the PAR curve shown in the graph below. This would be the perfect match for what the average plant requires.

However no (cheap) artificial light source by itself can do this so we opt for one that replicates part of the spectrum well and has some issues with other parts. For vegetative growth the lower regions of the PAR spectrum are of most importance (say between 400 and 550 nm), mostly blue and some green light spectra. For flowering/blooming plants we would want more yellow, orange, red light (550-700 nm) so we would try to replicate the higher range of spectra for them. A typical "daylight bulb" has a color temperature of 6500k (term for average spectrum of light related to temperature in Kelvin, based on the radiant energy from a black body). This bulb has the radiation breakdown in the visible spectrum (400-700 nm) shown below next to the PAR curve.

[ChrisK]

What I'm not getting is why the PAR curve doesn't drop off in the green part of the spectrum which is inefficiently used for photosynthesis.

edit: Here is the PAR curve I am familiar with and it's significantly different from above:

http://www.tomatoville.com/showthread.php?t=26446

I assume the first graph depicts photosynthesis rate (No Y axis labels) at each wavelength.

Originally Posted by sio2rocks

I'll Answer for hotwired since he isn't here right now. The PAR curve is the region of visible light between 400 and 700 nm emitted by our Sun that plants can use for photosynthetic processes. PAR stands Photosynthetically Active Radiation. The curve shows radiation energy in some units on the Y-axis that aren't important for our purposes. On the x-axis in the wavelength of light that those energies occur along the curve. So if we want a light source that is the perfect clone of our Sun we would want its radiant energy to fall exactly on the PAR curve shown in the graph below.

However no (cheap) artificial light source by itself can do this so we opt for one that replicates part of the spectrum well and has some issues with other parts. For vegetative growth the lower regions of the PAR spectrum are of most importance (say between 400 and 550 nm), mostly blue and green light spectra. For flowering/blooming plants we would want more yellow, orange, red light (550-700 nm) so we would try to replicate the higher range of spectra for them. A typical "daylight bulb" has a color temperature of 6500k (term for total radiant energy from light related to temperature in Kelvin, based on the radiant energy from a black body). This bulb has the radiation breakdown in the visible spectrum (400-700 nm) shown below next to the PAR curve.

[sio2rocks]

I think the reason why they look different from one another is because of the scales used on the x and y axes. In the one below the x axis is from 300 to 750 nm similar to the one on the link you posted, however the y-axis is on a real scale of light intensity uW/10nm/Lumen while in the link the scale is relative not absolute. The scale in the link for the y-axis is normalized to the actual output of the sun (peak output in blue range). This normalization changes the scale of the axis and vertically exaggerates the PAR shape. If you look at the two closely you can see the same peaks and valleys remain but they are further apart and definitely have more vertical depth to them in the one from the other page.

Hope this helps
Colin