The approximate cost is $25.00 per lamp.
If you would like more information than this instructable can provide, check out the website for this project. http://led.hypertriangle.com
When I finished this project, I was very satisfied with the results. The light produced from 87 LEDs is very usable. You can see graphs of lux if you are interested at the website above.
The best part about this project is saving energy. The 87 LED lamp uses a mere 8.4 watts! (0.7 amps @ 12VDC)
This project was seen at the Intel International Science and Engineering Fair (IISEF) and the Bay Area Science and Engineering Fair (BASEF).
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Step 1: Materials Required
T12 Fluorescent Tube Protector
48" x 1.5" x 0.25" Plexiglass
87 Super Bright White LEDs
29 2.7 ohm 1/4 watt Resistors
2.5m 18 AWG Bare Copper Wire
20cm 14 AWG Bare Copper Wire
1k ohm 1/4 watt Resistor
100 ohm 1/4 watt Resistor
0.2 microfarad Ceramic Capacitor
For the LEDs, if you are building your first buib, I recommend LED Shoppe. They have sweet deals on LEDs. The only problem is that they dont carry the most efficient or recent diodes.
For the bare copper wire, the 18 AWG can come from an old scrap of RG6 and the 14 AWG can come from Romex House Wiring.
The tube protector comes from most hardware stores.
Almost every other component there can be ordered from Digikey or Mouser
Step 2: Cut and Mark
You may need to adjust this step slightly to accomodate the tools you have available to you. To mark the surface of the glass, the strip of plexi-glass was clamped to a dry-wall "T" as shown below. Then using a utility knife and a general-purpose square, the marks were created. The dry-wall "T" used had fractional-inches marked on it, so they were used as a guideline as to where to create the marks. The first step in marking the glass is to go across the shortest side of the plastic, marking at regular intervals widthwise. Then the marks were created lengthwise. These second lengthwise marks could be omitted if extra car is taken in the next step if you want to make your plastic as mark-free as possible. The final product is shown below. This step is more of a general guideline. Your process will almost certainly differ. If you are marking holes for 87 LEDs, you will be creating 29 rows. This works out to approximately 1 3/8 inches between groups if starting 1 1/2 inches from the end.
Step 3: Drill
Step 4: Mount LEDs
Step 5: Add Resistors and Power Rails
Take some 18 AWG copper wire and being to solder it in place along the sides of the LEDs. Leave approximately 4 inches of extra wire on each end to work with at the end. Assuming you are starting with the positive rail, hold the copper wire against the LED's lead just slightly above the flattened area. This flattened area is a small "warning" that soldering below it can damage the LED, so try and stay above it. Now that the copper is held against this spot, fold the lead over the copper wire and solder. If you are bulding the 87 LED model, repeat this process 29 times until all of the LED triplets have a tie to the power rail. Then repeat this process for the resistors. The resistors do not have a "safety mark", so try and remain at least 1/4 inch away from the resistor when soldering. You will notice a 10 degree angle on the LEDs in this cross-section. This would be an ideal design that could make the lamp usable without a diffuser. However, this angle is not a requirement. It is difficult to drill accurate angles in the plexi-glass. In the bulbs that were built, the angle was omitted and the holes were simply drilled straight through.
Step 6: Create a Bi-Pin Connector
Step 7: Build the Current Regulator and Bi-Pin Connectors
It is not a requirement to use bi-pin connectors. You could easily wire up a simple DC socket. to the + and negative of the circuit.
(A new, clearer schematic is coming soon.)