CCFL Lamp - Page 1
Forum section: electronics / projects

author: Irukanji
author_rank: Contributor
timestamp: May 15, 2014, 01:27:15 pm
content: I was pulling apart some old flat screens and decided to make the basis of my lamp. Old CCFL tubes from the screen and the inverter unit from the same, few moments later bam, we have light. After some minor technical difficulties, I wrote an instructable on it.http://www.instructables.com/id/CCFL-Lamp/(copy/paste from instructables)Hello. The purpose of this instructable is to instruct people in the construction of a CCFL lamp. My current model might be a bit shammed together but this is only to illustrate the basic point.The things you will need areOld flatscreen monitor with CCFL lamps insideFlat screwdriverPhillips screwriver(star)Wire cutters or scissorsPower source, ideally a lab power supply or a hacked wall-wart capable of producing 12V DC or whatever your inverter needs to runElectrical tapeWhat 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 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 fun part: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 save one of the plastic sheets, one of the opaque ones. They all seem the same. There is some really cool, really small stuff in here. Mostly useless to DIYers.Now, the transformer/inverter. It's job is to take a set voltage(mine is approx 12V) 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. I had to cut mine out, you could also just remove the plastic section on the bottom and put the white sheet behind it, might make a useful tracing table or random ambient light source?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 :pThe heart and soul of the project. Without it, our lamps will never turn on. The tricky part is finding out how it works. These screens support PWM light 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. 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 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. Sometimes you can see transistors on the input which may be "ON" signals from the main control board, and a main positive wire. 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. When I make something more permanent I'll shrinkwrap it and stick a switch inline.The only bit left is to roll the opaque sheet into a tube(use the electrical tape or some clear sticky tape, and stick the lights inside of it. I have it laying down at the moment as I don't have the gear to finish making it. It looks much duller than it is, the camera auto corrected for the light. Good enough to read a book 3-4m away or stop you tripping over the pile of deconstructed computer screens sitting next to your desk.It does what I wanted it to do, it provides enough light to type this instructable to. Downside is they are fragile, but you could easily fit them inside a perspex tube. Inverter is a bit bulky, but a jiffy box is about the right size to fit them. 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 thurs night.If the light starts flickering, turn it off. Turn the voltage up .5V and try again. The main chip on one of the boards is a BIT3105, rated voltage 4.5V to 13.2V. 12V will be close to the right voltage, perhaps just under. Some newer screens have wider operating voltages(up to 36V it seems), so check some part numbers before blowing up your board.I intend to stand it upright on a base, the wires and lights could fit inside a transparent tube of some sort, which can be supported within the opaque sheet with some wire. The inverter should be in a box, ideally with a DC jack so you can use your power supply for something else.Thats it, hope you like it.I figured out how to find positive/negative from watching the EEVblog videos, the books "The Art of Electronics", and some other bits and pieces. Thanks Dave et al.There is some other cool stuff inside the screens, but most of the electronics are of no use to use unless you really need some tiny no-name surface mount stuff.http://youtu.be/kdtyxt9OLlUThe basics are the same for the screen part, but it uses LEDs instead of CCFLs.

author: miguelvp
author_rank: Super Contributor
timestamp: May 16, 2014, 01:38:03 am
content: Nice, you can always get one of thesehttp://www.performance-pcs.com/catalog/index.php?main_page=index&cPath=72_95I used the inverter of those cold cathode kits to make an emergency nightstand with the CFL tubes from bulbs that didn't work anymore.Edit: Inverter by itself cost around $4 in a safer case than not in a box. And the bulbs with the guts out are pretty light and sturdy.