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LED Lighting - DIY Style

11K views 46 replies 10 participants last post by  Geomancer 
#1 ·
So I'm an Electrical Engineer by day, novice aquariest by night.

I've been thinking for weeks of something practical I could make at home that wouldn't cost exponentially more than just buying it pre-made off the shelf.

Then I had an epiphany! LED lights to grow plants! Genius!

So I went to my favorite parts supplier and lo and behold they did list kelvin ratings, awesome. So I searched for everything between 6000K and 7000K. Got lots of results. Perfect!

The question then becomes of intensity, and how on earth do you compare LEDs to incandescent (or even fluorescent) lights.

The brightest option was a 850 lumen LED at 6300K, 11.8W. Not bad at all. Now, if I look at a table of lumen's versus watts for incandescent lights that makes it equal to a 60W bulb (or 14W fluorescent).

Does that make sense in my logic? That's one heck of a lot of light coming from a single 12mm (half inch) diameter LED!

The issue, of course, is cost. These suckers cost $26 each! However, I was only looking at the top of the barrel. Lower intensity LEDs are of course less expensive and I'm sure I could find a more cost effective $/lumen. Still, a couple of those and it isn't going to be more expensive than buying a pre-made one (A 5 LED 19" @ 6500K marketed for growing plants is $136 and is only 12W).
 
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#30 ·
Thanks, it's pretty basic. I could of painted it for a better look, or put it in a box instead of just a sheet, but it's just an experiment. I don't even know if it will work yet (for growing plants that is).

I'm not mechanically inclined (in the least) nor very creative in visual appeal, I'm more of a practical person =)
 
#31 ·
I think its looking pretty fly :)

What was the overall cost of the final build? Id be interested to see regular updates of your plants progress so we can do a cost/benefit analysis.

what voltage are you feeding with that transformer plugged into the back?
 
#32 ·
There is no transformer, if you are meaning the two big black things on the back of the PCB those are power MOSFETs with heatsinks. The power coming in is from a laptop power supply set at 19.5V.

Here is the rough BOM:

2x Heatsink - $4.62
2x LED - $10.52
2x NPN Transistor - $0.06
2x N MOSFET - $2.58
2x 2 ohm 1W resistor - $0.17
2x 100k ohm 1/4W resistor - $0.04
2x Zener Diode - $0.08
2x TO-220 Heatsink - $0.78
1x Power Connector - $1.77
1x Toggle Switch - $2.50
1x PCB - $3.99
1x Universal Power Supply - $10.69
1x 12x24 HDPE Plastic - $12.45
Various Hardware - $5 (screws, spacers, etc)

Total: $55.25

Tools/materials needed:
Wire (22-24 AWG)
Solder
Solder Iron
Solder Flux
#4 tap
Screwdriver
Socket Set/Wrench Set (Adjustable wrench, really any kind of small wrench for the nuts)
Saw (Cut plastic to size & cut circular hole - A 2" hole drill works)
Drill

If you don't have any of that, you'll have to add the cost or find someone to borrow from. As you can see, the plastic and power supply are two of the biggest costs. If you already have something you could substitute (metal, wood, plastic, whatever) that saves you $12 right there. If you already have a spare laptop power supply, that could be $10 off assuming the voltage is workable. For these particular LEDs it had to be at least 19V.
 
#33 ·
It's been a couple days over a week, but here are the differences.

Day 1:

Today:

The plants are for sure growing quite well, I've noticed quite a bit more growth so I'm confident the LEDs are working as intended. So I guess that means the experiment was a success which is great!

Another sure way of knowing that the plants are reacting is the Wisteria. This plant really changes its leaves according to light and in this picture you can see new leaves that are significantly broader than the existing leaves.

 
#35 ·
The zener is just a precaution as the absolute maximum Gate to Source voltage (Vgs) is 20V, and my power supply is set at 19.5V +/- 5%. So the zener just cuts that down.

The typical forward voltage of each LED is 18.1V, and the target current is 350 mA for a total power of 6.3W per LED.

The MOSFET acts as a variable resistor to ensure that, regardless of the input voltage or the current setting resistors value (tolerances) the LED will see a constant current. A heatsink is probably not necessary, with it the transistor gets warm to the touch, but not hot enough to burn.
 
#37 ·
The Red Tiger Lotus is thrilled with the light. It is sending out a new leaf every 2 to 3 days and shows no signs of stopping. All of the leaves are staying close to the substrate, none have made any attempt at reaching the surface.



Actually, everything is doing well. The crypt melting quite a bit, not I'm glad to see it's stopped and left a few leaves. It should spring back in no time.



At this point I'm reasonably pleased with the outcome, and as a proof of concept so far it has been a success. it is possible to do a DIY LED fixture, and at a price lower than comercial options. Not much lower, but I feel satisfied.
 
#40 ·
I have to wonder if the assembly could be modified to hide in a rain gutter.. hmm.

One of these days ill get part numbers from you and build my own just for kicks, but im DONE with wiring for a year. I do alot of maintenance for the FD, and in the last week I have had 1 blinker circuit fail, 1 electric siren driver fail, and one light bar fail 3 times now (for a yet to be determined cause). No to mention I have 3 personal vehicle installs lined up. If I see a wire anytime soon im going to have a break down. :lol:
 
#41 ·
That tank is lovely, nice work.:nicefish:
 
#45 ·
This is where I got the basic idea: Specs & Function

since they looked better under the cool white, have you thought about just adding 3-8 (cheap) blue LEDs to help balance? make sure they're wide-angle, and somewhere close to 460-480nm would be ideal for PAR...
I haven't thought of adding anything more. "Regular" led's wouldn't be bright enough, and power LEDs would need the heatsinks and another constant current source. So it isn't as easy as just plugging them into the existing circuit.

These LEDs have their peak intensity in that range already though. It's actually red that is really lacking with these LEDs. On the first page of this thread is the color spectrum.
 
#44 ·
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