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New to growing your own tomatoes? This is the forum to learn the successful techniques used by seasoned tomato growers. Questions are welcome, too.

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Old February 15, 2015   #1
Cole_Robbie
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Default My $18 grow light

Actually just the bulb is $18. The rest of it I scavenged from junk. I wanted to make some new lights for starting seeds.

This is the bulb:
http://www.menards.com/main/electric.../p-1856945.htm

It's a 65W, which is 200W equivalent, in "Cool White," 4200 Lumens at 4100K. Menards had a 300W equivalent, but it was in Day Light and not Cool White.

I had an old socket, but a new one is $1.71 at Lowe's:
http://www.menards.com/main/electric.../p-1856945.htm

The socket will take any normal bulb. The 150 watt equivalent cool white spiral CFL is another decent choice; it's about half the price. I wired the socket to an old cord from a computer monitor that died. I made sure to look up the carry capacity of the wire, but I am only running it at 10% of it's maximum load.

The socket is attached to a scrap of plywood with a hole cut in it from a hole saw so the bulb can poke through. My reflector is a plastic Rural King bucket cut in half. I used an oscillating saw to cut the bucket in half. A hack saw or coping saw would probably work, too.

http://i.imgur.com/4V4Kwkg.jpg
http://i.imgur.com/iPSxrM2.jpg
http://i.imgur.com/5rubq5P.jpg

By buying just the bulb and making everything else, the light ends up being 1/2 to 1/3 the cost of buying a pre-built grow light.
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Old February 15, 2015   #2
noinwi
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Nice! Similar to what I used to use. Someone had given my DH a reflector but no innerds. He added eight sockets(that he already had) to it for regular sized CFL's. Used it for several years but had to leave it behind in Wisconsin.
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Old February 15, 2015   #3
lexusnexus
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Nice setup. Does that reflector provide enough light? Would some sort of aluminum foil or likewise augment the reflected light?

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Old February 15, 2015   #4
Cole_Robbie
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Thanks.

White works pretty well as a reflector. I suppose I am losing the light that leaks through the translucent bucket, but I don't think it is much. Painting the inside of it with flat white paint would be a slight improvement. The best reflective material is mylar, at about 96-98%, but flat white can reflect about 90%. Mylar starts to lose that edge as soon as it becomes wrinkled or dirty.
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Old February 16, 2015   #5
taboule
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Creative and practical, i have a few similar setups I've concocted wit spare parts. Anything to save a buck -while keeping it safe of course.
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Old February 16, 2015   #6
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Thanks for explaining. I'm always learning something out here..

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Old February 16, 2015   #7
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I cant wait to see this thing/contraption at work.

I have considered putting some in a row on ceramic fixtures.
The curve of the reflector gets me to thinking about focal points.
If the plants where placed at the focal point or just inside it the light would concentrate there.
So lets say you had a curve with a diameter of 4 feet the focal point would be 2 feet or half the diameter of the curve.
This would also be the radius.
With this in mind I think a reflective dome would be the best reflector to place the plants under.

By looking at the last picture I can now see that much of the light is being trapped inside the reflector because the bulb is just about right at the focal point.
Since the bulb is also round the upper half of the bulb is sending light out to the reflector and bouncing it right back into itself.
Just a thought.

One question, why not the bright daylight, that is what I have always used.

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Last edited by Worth1; February 16, 2015 at 10:45 AM.
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Old February 16, 2015   #8
Cole_Robbie
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The cool white bulbs are more blue. The day light work, but the ones I have had are more reddish in light. Do you remember the guy who posted on here under the name 'Hotwired'? He was an optics engineer, or something over my head like that. He made spectrum graphs for bulb makers. I remember he recommended the cool white.

The reason that white works as a reflector is mostly for its ability to diffuse and scatter light. If you look at a commercially made grow light reflector, the metal is textured, and not perfectly smooth like a mirror or mylar:http://www.amazon.com/Lightwave-Comp...dp/B0037Z8GOM/

So concentrating light into a focal point is not as beneficial as scattering it around. I have also seen commercially built reflectors that are white inside, and those are not textured. The flat white color diffuses as it reflects.

One of the fixtures I have used doesn't even have a reflector. It's just a dual socket for an outdoor security light. The big cfls seem to provide enough light that having a reflector at all is optional.

I did look at bathroom vanity fixtures at Menards. They had a five-socket one for $15. That's not a lot more expensive than buying ceramic sockets to wire.
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Old February 16, 2015   #9
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I've always used flat white as a reflector and have for about 30 years.

I was thinking about not the focal point but inside the focal point.
That way the light would not only be coming to the top but also to the sides of the plants.
My idea was to evenly distribute the light so the plants wouldn't lean towards it.
Just more of my wild ideas and not to belittle your setup it looks nice.
Just thinking in circles again.

I wonder where old Hotwired went.
It looked like he was trying to sell his irrigation set ups and then left.

Worth
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Old February 24, 2015   #10
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LED's are the future. Look into COB's. All directional and no wasted light unlike CFLs.
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Old February 24, 2015   #11
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Quote:
Originally Posted by borgman View Post
LED's are the future. Look into COB's. All directional and no wasted light unlike CFLs.

I have made them the present, every light I buy now is LED as soon as the CFL lights burn out.

Looking forward to setting up an LED grow light systems to start seedlings too.

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Old February 24, 2015   #12
Cole_Robbie
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LEDs are the future, but they are not the present, at least as grow lights. I've seen one impressive LED system posted on here, but the builder was an electrical engineer by trade. I got the impression building it involved a little more skill than my junior high school science project level of knowledge of electronics. And I know they get better all the time, but I'm still yet to see an over the counter LED system be more cost-effective than other forms of lighting. It's coming, but I don't think we are quite there yet.
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Old February 27, 2015   #13
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I have 3 units of twin tube T8, 48". Each unit cost me about $20, including the bulb. Each bulb has 32w rating.
I have 6500k daylight deluxe, which is on the BLUE side. From what I have gathered the blue spectrum is good for seedling growth where you don't want flowering and fruiting.
This is the second season I am using them. They are compact and at the end of season I just pack them into the original box.
It works great for my needs. I grow about 30 peppers and about 30 tomatoes.
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Old February 28, 2015   #14
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Keep us posted on how the seedlings react, compared to using fluorescent tubes.
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Old February 28, 2015   #15
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I've been using CFLs for years. It's the same light as a fluorescent tube; it's just more concentrated into a smaller area.
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