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In this instructable, I will try and outline all of the steps required to create an LED fluorescent replacement tube. This instructable is provided more as a guideline, you can change almost anything in here to suit your needs. The lamp I created contained 87 LEDs, and this guide provides instructions for that many. This instructable contains the information on how to build a lamp, but there is too much information about how it works to include here.

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).

Help us out and digg this story!

Step 1: Materials Required

You will need an array of materials for this project.

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
Solder/Flux
LM334
TIP32C
ZTX948
1k ohm 1/4 watt Resistor
100 ohm 1/4 watt Resistor
0.2 microfarad Ceramic Capacitor

Suggested Suppliers:

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

A standard fluorescent tube is approximately 48 inches long and 1.5 inches wide (T12 = 12 * 1/8 inches wide). Take your sheet of plexi-glass and cut a piece that is 1.5 inches wide by 44 inches long. 4 inches is left in the tube for the current regulator and wiring in the ends. This is best done on a table saw while wearing all appropriate safety equipment. If you do not have access to a table saw, consider using a plastic laminate scoring knife.

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

This process is best done with a drill press. If you are creating an 87 LED bulb like the one designed, it will take approximately 20 minutes to drill all of the holes. Grab a piece of scrap lumber and clamp it to your drill press's stage. Align it to be square to the drill press stage, and the correct distance to ensure that all of the holes drilled fall in the same plane and on the score marks. The ideal drill bit size to use is 3/16 inches. This size is slightly smaller than required but allows the LEDs to be mounted without glue. This is where you can omit the lengthwise score marks by ensuring the jig is clamped in the correct location.

Step 4: Mount LEDs

Its now time to mount the LEDs. Grab your bag of LEDs, and insert three into a row. Ensure that the polarity is kept constant. All of the positive sides (longer lead) should be on the same side of the plexi glass. Next using needle-nose pliers, bend the leads into a square as shown in the picture below. Next, solder the leads together. Repeat this process for the other touching leads. The resulting soldered connection should be enough to hold the LEDs in place. Trim off any excess lead, but leave the main (+) and (-) long as shown in the picture below.

Step 5: Add Resistors and Power Rails

Next, grab your bag of 2.7 ohm 1/4 watt resistors. Trim one side of the resistor down to 1/4" and trim the (-) side of the LED triplet down to 1/4". Solder the two shortened leads together. Repeat until all of the LEDs triplets have a resistor. The reason this resistor is 2.7 ohms is due to the current regulation circuit. The LM334 (the main component in the current regulator) has a reference voltage of 64 mV. A simple ohm's law calculation can determine this resistor value. 2.7 ohms ensures that each LED gets exactly 23.5 mA.

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

A Bi-Pin Connector is the most common type of connector used in fluorescent lamps. The bi-pins commonly used have 12.5mm between two rigid pins. To create these connectors, take a piece of scrap wood and drill two holes approximately 12.5mm apart. It helps to use a drill press and digital caliper, but it can be done with a ruler and hand drill. The depth of these holes is not important, make them at least 1/2 inches deep. The holes should be 1/16 inches in diameter. Cut two 5 cm pieces of 14 AWG bare copper wire. Insert the two pieces into the drilled holes. Slip the end cap from the tube protector over the two wires now stuck into the scrap wood. Twist the two loose ends of the wire together ensuring that the other ends remain in the scrap of wood. Prepare some low-temperature melting plastic. This is usually done by simply boiling some water and pouring the granules in. Pour the molten plastic into the end cap making sure that the plastic is at least 3/8 inches deep and distributed evenly throughout the cap. Allow the piece to cool and when the plastic is fully cooled and hard, remove it from the wood. Trim the two wires coming out of the end cap to approximately 3/8 inches. You should now have a replica bi-pin connector that can be slipped into the end of the tube protector with no effort at all. Repeat this process to create another end-cap. When you have two completed, mark one as positive and the other as negative using a marker.

Step 7: Build the Current Regulator and Bi-Pin Connectors

Build a current regulator as per the schematic shown below. You can design PCB artwork or build it on some proto-board. The LED mounting plate should now be populated with LEDs, resistors and power rails. Slide the mounting plate with all of its components into the clear tube protector. There are three terminals on the current regulator: (+), (-) and a tap. Connect the loose ends of one side of the power rails to the (+) and (-) holes on the PCB ensuring that the polarity is correct. Take a short piece of wire of any gauge and connect it to the first LED triplet between the resistor and the (-) side of the LED. Connect the other end of this wire to the tap on the PCB for the current regulator. This is the "tap" used to regulate current. The next step is to take a short piece of 18 AWG wire and connect the positive bi-pin connector to the input trace. Take the negative bi-pin connector and connect it to the negative power rail on the opposite end of the tube. This is the rail with the resistors installed. Trim all wires to be as short as possible. The final step in creating the LED lamp is to slide everything into the tube and slip the bi-pin connectors into the ends. Ensure that they are aligned with each other.

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.)

Step 8: Variation: DC Socket Instead of Bi-Pin

You can easily use a DC socket instead of a bi-pin connector. The pictures below explain it better than words can. Simply connect the positive and the negative connections in the circuit to your barrel plug.
I thought that was a lightsaber in the thumbnail!
CAN U TELL ME WHY WE USE TRANSISTORS IN LED CIRCUIT, AND CAN U SEND ME THIS TUTORIAL CIRCUIT DIAGRAM PLZZZZZ <br><br>I HV MANY QUESTION TELL ME IN PERSONAL MSG.... <br><br>
No. <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br>Now go off on your merry way and learn how to speak correctly.
Problem: Directionality of ordinary LEDs makes this a spotlight, unless a diffuser is fitted..<br> <br> Solution: Use &quot;Strawhat&quot; LEDs, which give are designed to give a much wider spread of light.<br> <br> (By having the LED source much closer to the end of the lens.)
Hi there.<br><br>How did you &quot;difuse&quot; the led's?<br><br>Thanks
To increase the viewing angle? Use sand paper.
why you did not use SUPER FLUX LED , Did you tested it ...? See drawing & make one tube . after use this tip you will gate more light than your tube ..
What is the advantage of using an LED pattern like this? Does it affect light scattering?<br />
Yep this will Give more light without dark lining . <br>try it , make it and compare . <br>i promise this will give more light .
Ya. this will effect . you will have more light .
I am very interested in building on of these just to compare to a normal tube<br>After building do I just replace the normal flourescent tube with this? Or will I need to make some adjustment to the balast? also as I am in the UK do I build the small circuit as is or do I make some changes?<br>
where can i find this circuit diagram???
Er,where (in the UK) can I get hold of such as thing as a "T17 fluorscent tube protector?"
Its T12, and you can get them at most hardware stores for around a 2 bucks - they are a pretty common place object. They are used in those convenience store fridges with milk in them so that if the tube breaks, the glass is kept (relatively) intact.<br />
very clever indeed!!<br /> Now what is the limit (down and up) of LEDs you may use? Lets say if you should replace a 4W lamp? <br />
i'm not sure that I understand your question.&lt;br /&gt; &lt;br /&gt; If you are asking how many LEDs you can fit into a tube, it is up to you. As many as you can fit is the limit, just make sure you heat sink that circuit because with each additional LED, it runs hotter and hotter. With 87 LEDs, it dissipates approximately 3 watts of heat. &lt;br /&gt; &lt;br /&gt; A general rule of thumb is that you need 1inch<sup>2 of surface area per watt of heat generated. Use copper if you can.&lt;br /&gt; &lt;br /&gt; &lt;br /&gt; Maybe clarify what you want to know... I would be glad to answer.&lt;br /&gt;</sup><br/>
If one so clueless, just forget it.
Incredible idea. Will it light a room as well as a mercury tube?
Depends on the size of the room. From personal experience, a 10 x 10 room can be dimly lit if a diffuser is used. This lamp is ideally installed over a work bench to provide bright light on a spot.<br/><br/>However, if you are willing to spend the time when these lamps are used in multiples they are very capable of lighting a room. I created four of these lamps for our project and we lit an entire room with three of them. The reason is because they are highly directional with light only coming from 20 degrees of the entire lamp.<br/><br/>Thanks - check out our site <a rel="nofollow" href="http://led.hypertriangle.com">LED Ideas</a> There are more pictures and graphs of light intensity.<br/>
I see. So, if I decided to point them in all directions instead of one, it would light more of an area?
That is actually one of the intended installation. If you had 2 tubes in a fixture, you would aim them apart from each other to provide light to the whole room. We tried this, and it works good.
One way to have the holes face away from each other would be to place the strip on an old binder when you drill the holes. That should give you 10-20 degrees of tilt.
Gotcha. Definitely a project I'll be trying in the future.
what kind of diffuser did u use? and what are other alternatives? thanks :)
We created our own diffusers by taking a plastic tube protector and giving it a light sand with a high-grit sand paper. Check our site in the near future for more information about this.
Wonderful build. I picked up some 1 amp led mains drivers from dealextreme for 3 bucks...definitely a good idea to use them for!
Link, please.
<a rel="nofollow" href="http://dealextreme.com/details.dx/sku.13552">http://dealextreme.com/details.dx/sku.13552</a><br/>
Thanks! hehe Imagine building this with a set of these <a rel="nofollow" href="http://www.dealextreme.com/details.dx/sku.11809">12W puppies</a>. You'd want a 120mm tube, so you can fit the heatsinks and fans at each end. :D<br/>
Adding to my comment. Pictures done with dark street, no flash and no other lights on. Just THREE of my "light points". Connected to a battery of my "experimental small solar supply" (15 W solar pannel to a 7A/h battery). Total of the three lights drain 300mA. The led single rows, with the same connection method are still to be finished as environmental light to watch TV.
At 10 inches distance gives 4000 lux (+/- 3%). At one meter 480 lux, enough to read a book or a newspaper. Ceiling light gives, at my dining table level, 225 lux easy to eat, but not enough if a fish in in your dish.
There is a problem with driving LEDs at a variable voltage... As the input voltage changes, the current through the LEDs changes. This can cause premature failure and brightness variation as the day goes on.
As the lights are used night time and solar panel is off, the voltage starts at a full battery (in my case 13,65 vdc - nominal float voltage), that means the voltage is only decreasing with the use. The worst for LEDs is the voltage up/down variations, in this case it goes only down very slowly. As I wrote, two full months working this way and no failures... let's see after one year.
Very clever project! One thing that is not clear to me is the power source--can this be inserted into a fluorescent fixture as a direct replacement, or must the fixture be modified (as in remove ballast & rewired) in order to use the led version?
Well, there are two installations that can be done. One is to install a switching mode power supply into the fixture in place of the ballast. The other is to completely remove the ballast and wire up an alternative 12 volt source such as the batteries in a solar or wind energy based home. The second method is preferred for many reasons.
Now plug it into the lamp socket and watch the thing go up in flames because you forgot to remove the high voltage ballast! Very scary project.
Well done, I think I'll try to make my own one
Yes a good question I too have the same question.
something is missing... what's the power source? I'm certain you don't run this off the ballast in a standard fixture, but since you don't directly say I can see someone assuming you do.
I am thinking simply bypass (unwire) the ballast and wire directly to the AC source. For this reason I like his variation of using the DC socket instead of the Bi-Pin connectors. For my intended application of this in fact I am going to forgo the tube altogether as everything is going to be contained within a ceiling mounted plexi light box in a (cold in winter) laundry room. Good Luck.
It is any 12 volt source, preferably 12 volt battery charged via solar panels.
Providing you use high brigth white leds (nominal 3.5vdc 20mA) FOUR of them in series enlightens properly from 10 up to 14 vdc, always within the range of a battery or power solar system. I've connected in paralel 5 rows of 4 leds and it works. No regulation or resistor needed. Two months working no fail, only slight dim under 12 vdc.
In a three led row (as in your flourescent tube) and to achieve top brightness, one 120 ohms resistor per row will do... if voltage remains under 14 vdc and if power is from a battery. Never from a mains AC adapter, as their floating voltage can rise to 17vdc when designed to work with a 12 vdc appliance, also the (quite always) remaining AC is no good for a led.
Hello guys! Have you ever consider to use SMD LEDs? I mean the kind we find in cell phones, the ones that light the main LCD display. They are usually cool white and are REALLY bright, though they use lower voltage and current. I`m doing a bed lamp for my wife, as she likes to read and suffer from imnsonia, and those 9 watt PL lamps doesn`t live long enough... And my cousin has tons of old cell phones to salvage... Best Regards dudaott
These types of T8-based tubes are commercially available for ~$65.<br/><br/>A good application is lighting cold rooms or unheated garages where fluorescents can't work.<br/>Good white LEDs can put out 132 lumens per watt, while fluorescents are only 65 lumens, and full of poison gas. (incandescent is 15 lumens/watt -meh)<br/><br/>I've seen prototype LEDs from Nichia output 250 lumens/watt.<br/><br/>Small factoid: if the US went to LED lighting, it would save $115B by 2025, shut down 133 power stations, and prevent 258 million metric tons of C02. <br/><br/><em>(Science Magazine, 325: 14 august 2009, p.809)</em><br/>
2.7 ohm is probably not enough for current limiting on the individual strings of 3. Your one string that is connected to the reference of your regulator will have the proper current, but the rest of the strings may have significantly different currents, especially if the temperature is different at one end of the tube as it is at the other. On its own, the end with the regulator will be warmest of course, so it shouldn't be a big problem, as the reference LED's will be the warmest (highest current.) If you have LED's with different Vf's, you may get significant variations in current between strings though.
where did you get the leds from
A company called ledshoppe (google them) I ordered 1000 for 89 dollars which works out to 8.9 cents a piece. They are cheaper now though, I ordered 1000 about a month ago, and they were 59.
thank you
WHAT!?!?! in my town The Source sells them INDIVIDUALLY for 5.99!!! just goes to show that the net is cheaper! :P

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