Intro: CCFL Lamp
Hello. The purpose of this instructable is to instruct people in the construction of a CCFL lamp.
The things you will need are
- Old flatscreen monitor with CCFL lamps inside
- Flat screwdriver
- Phillips screwriver(star)
- Wire cutters or scissors
- Power source, ideally a lab power supply or a hacked wall-wart capable of producing 12V DC or whatever your inverter needs to run
- Electrical tape
What is a CCFL? Basically, there is no filament like in a normal light. The idea is it requires less hardware to keep running since it doesn't need a voltage to keep the filament hot(like in valves). So a simple DC stepup inverter is all you need. This takes your humble 11-13volts(or more/less, depending on type) and steps it up to an amount high enough to excite the gas/vapour in your tubes(mercury) and cause the phosphor coating to fluoresce. The result is a bright, white light. Like the lights found in practically every supermarket/store around. Except miniature.
Step 1: The Extraction
Find an old flat screen monitor. Any brand will do. If you find an LED screen, lucky you, but this instructable won't really apply.
The idea is simple; to take a working but unwanted flat screen and make something useful with it instead of just throwing it all in the rubbish. So, undo your screen case. I don't have pics of this bit, it's easy enough. For my screens I had to separate the 2 halves with a screwdriver and ripping it apart. Under this was 4 screws holding the panel on, and then a bunch of plugs on the other side.
Now you have 2 pieces, you should work on the glass bit first. Disassemble the whole thing. It's straight forward, bunch of clips, nothing new if you've been tinkering for a while. In here is a sandwich of plastic sheets and plastic(and an LCD screen). You want to remove 2 of the opaque sheets. They all seem the same. There is some really cool, really small stuff in here. Mostly useless to DIYers. My attempts at removing the voltage regulators ended in a destroyed regulator, it appears a conventional soldering iron will destroy the chip before it gets hot enough to desolder it.
One side of those sheets is shiny/smooth. Remember this.
Now, the transformer/inverter. It's job is to take a set voltage(mine is approx 12.8V) and step it up. CF tubes run at very high frequencies, and this board will take regular 60Hz and make it several thousand times higher. In mine it was a separate board, held on by a screw. I destroyed one by ripping the plug off. You'll need wire cutters for this(ideally), or scissors. Cut it away to leave the most wire on the inverter plug.
The lamps themselves are at the top/bottom or sides, you'll easily recognise them. If you look carefully, there are 2 small screws on the back. These hold the lamps in, and make their removal easy. Everything inside these panels is designed to be as thin as possible. Screws are short, a lot of stuff is snap on. Don't do this to your parents one if you need to have it back together by 6pm when they get home; there is a good chance of something breaking.
Step 2: The Inverter
Disclaimer: The inverter is quite dangerous, a few hundred volts at a few tens of milliamps. If you don't want to get shocked, keep your hands clear when it is on. Don't say I didn't warn you :p However it seems hard to do, everything is relatively well protected.
The heart and soul of the project. Without it, our lamps will never turn on. The tricky part is finding out how it works. These boards support PWM dimming, so a few of the wires will be control channels from the microcontroller on the other board. 1 or 2 other wires will be negative, and 1 or 2 will be positive. Out of these 2 boards, the negative was on the left on one, and in the middle of the other. The negative is easy to identify: Hold it up to a light source and that big trace running along one side is probably the negative(sometimes the majority of the space will be ground). On the other side, a fuse is generally a good sign it is positive.
On these inverters there is a big test pad(left of the picture, also visible around screw holes), hook the ground up here(aligator clip). Doesn't work through the wire for some reason. Now, hook up the positive of your power supply to the positive wire. If you have banana plug stackers, you can test multiple pins at once to see which wires need to be connected for it to work. Just run them along until the screen flickers once and then go from there.
Sometimes you can see transistors on the input which may be "switches", and need a signal from the main control board, and a main positive wire(2 wires lead to opposite pins of a transistor, with the emitter(presumably) heading off to the other side of the board. Try not to short circuit your power supply.
The coloured wires top left/right are connected to the CFL tubes, the plugs only go in one way and it doesn't matter which connection goes in where. Bottom right is the plug connecting to the board. Left is connected to ground but doesn't permit the circuit to turn on for some reason, wires 1, 4 and 5 are twisted together and connected to positive(disregard the black wire).
Step 3: The Finished Product
After playing around for a while, I have determined that the most robust light source comes from the housing itself with the LCD panel and opaque sheets removed. Leaving a single sheet is desirable, as the plastic with the etched dots looks weird and the light drop is tolerable with the sheet. Check the opaque sheets also, one side is smooth and one side isn't. Make sure the smooth section is facing down/touching the etched plastic piece. Seems to help with getting the light out, but adding extra sheets reduces the brightness noticeably and aren't worth the effort.
The major downside with this is that the screen is quite heavy, which leaves a problem of standing it up. In the picture you can see it is just leaning up against the power supply.
The picture makes it look dim, but it is enough to illuminate the entire workbench.
Step 4: Moving On
Most of the original hardware can be snapped/screwed back on, which gives you a few options for mounting. The original screw holes in the corners may be useful for attaching to the underside of a shelf if you have one, to provide a sort of mini floodlight which will illuminate a medium size desk nicely with minimal "sideways" light.
It does what I wanted it to do, it provides enough light to type this instructable by. The lamp 2.0 using the original screen is much more mobile, the inverter will tape to the back cover nicely to keep it relatively flat(insulate the bottom of the board with some tape first).
The inverter is only about 10mm thick, which makes mounting it easy on a wall/flat surface with a few standoffs. Ideally you'll have it in a box, to protect the wires from snapping off(or from zapping yourself/spilling things on it/etc). A small 240V to 15-24V transformer to power a small LM317 circuit and use resistors to set it at the correct output voltage(I'm running it off a LM317-based power supply without issue, about 12.8-13V. A LM7812 might be more suited to lower power inverters, just keep an eye on the heat. Alternatively, a power pack would be more suited to keep the profile low(12 and 15V are common) and either use this to power it directly or use the same circuit above and adjust the power pack output accordingly.
So yeah, a little hack to make a decent light. I intend to do some research into PWM dimming, without the PWM signal the lights will remain on 100%. The datasheet is your friend, the circuit is simple enough to understand, easy project for a boring night. If the light starts flickering, turn it off and turn the voltage up .5V and try again.
PS: Throw everything into the recycling bin if your area has collections. The plastic and steel will be reused, and the boards may be processed to retrieve the gold or other materials left in there. They are usually thrown into landfill because disassembly is too costly.