Instructables

Free Cold Cathode Lighting

Picture of Free Cold Cathode Lighting
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This is a description of how I made a small cold cathode lamp for free. I hope you enjoy it!

Scanners use cold cathode lamps to illuminate the images that they are scanning so that a special IC (Integrated Circuit) can scan them. In most cases, when a scanner breaks, part of its scanning and/or computer connection hardware is damaged, but the cold cathode light and power inverter are often in pristine condition. By extracting them and wiring up a simple circuit, we can get ourselves a virtually free (Unless you were forced to pay a few dollars for the broken scanner) cold cathode lamp.

First, I took apart the scanner, and removed all of the circuitry. Then, I removed the stepper motor and took out the light assembly. This is probably the only part that you will need (unless you decide to reuse some switches and power connectors from the main board of the scanner). Next, I extracted the cold cathode lamp and its power inverter (a small circuit board with a transformer and some capacitors and coils). After that, I stripped the input leads to the inverter, connected the scanner's original power supply to the wall, and used the stripped leads to test the lamp. Note that ifyou connect the leads the wrong way, you will destroy your power inverter and you won't be able to continue. To see which way you need to connect your wires follow these instructions:

1) Look that the colors of your stripped wires. The black one is ground (negative -) and the other colored one (often red) is the positive input (+).

2)After you have determined the polarities of the input terminals to the inverter, look at your power supply (the one that plugs into the wall). There should be a small diagram that you can see in the top right of the second picture in the slide show. It will tell you whether the outside and inside of your power connector are positive or negative.

Once you have figured out all of your polarities, simply hold the input wires of the power inverter onto the correct sides of the power supply connector. If you did everything right, the cold cathode light should light up. If however you connected something the wrong way, you will see some smoke come out of your power inverter and that will mark the end of its life.

Once you've gotten the cold cathode light to work, simply solder on a power switch in between the power inverter's inputs and the power supply's output. After that, add a female power connector so that you can plug in and unplug your power supply. Once you've done this, I recommend using hot glue to cover up all of the contacts (to prevent any unnecessary electric shock or accidental contact)
and mounting everything inside of a project box (I used an altoids tin).

And... You're done!

Possible applications include:
1) Using to illuminate computer cases; use this instead of a $15 commercially sold cold cathode lamp)
2) Book light
3) Computer keyboard illumination
4) And much, much more!

PS: Instructable coming soon!
weargle2 months ago

i see i lightsaber coming

tech-king5 years ago
id just like to point out: that inverters output is not 0 or 50-60hz. you cannot salvage the lamp and attach it directly to 12 volts. you need that inverter. nice ible.
Its because of the voltage the tubes require to run on as well. They use a few hundred volts
cupnoodles23 years ago
hello i recently got one from a multifunctional canon scaner and got it working
id just like to know if there's a chance that looking directoly towards it can damage ur eyes? i wanna make it a gift but im afraid i can hut her :S
thanks for your response
Xellers (author)  cupnoodles23 years ago
Nope, there should be cause for concern, as far as I know. Of course, staring into any bright enough source of light can cause damage, but I don't think this should be any more dangerous than an average lightbulb. If anyone else knows better, feel free to correct me, though. Good luck!
its2l8men3 years ago
i have a cold cathode tube from an lcd monitor how can i hook it to the battery?
Xellers (author)  its2l8men3 years ago
You need an inverter to power your tube. The tube will have been connected to a small circuit board with a transformer and (usually) a pair of transistors. If this is so, then find the power connections to that inverter and you're in business; if, however, the inverter board has other electronics, then this may become tricky. Usually, you can still isolate the inverter part and bypass the control electronics, but if this is not the case, then you may need to build (or buy) your own inverter. Check to see if you can get it working without building anything yourself, and if not, then send me a message and I will be more than willing to help you. Good luck!
its2l8men3 years ago
i have a ccfl from an old laptop, and it has 10 connector leads how do i hook it up to a pwer source
its2l8men3 years ago
and my inverter has 10 connector leads, what will i do w/ those and by the way the rating was 12v
reubenfaber3 years ago
Just wondering... since this is a flourescent light bulb, and not one intended for general lighting, is there a UV filter built into the bulb? If not then we could be exposing ourselves to possible damage to our eyes. I built one of these lamps with an old scanner ccfl bulb and inverter, out of plexiglass and a computer fan to cool it... it's pretty sweet.
zack2473 years ago
i killed a power inverter by accidentally hooking it up backwards... now im stuck with a cold cathode tube and no inverter for it!
yes, just watch, they also have all of the flexibility and stability of a house of cards, and if they break, its hazmat time "mercury dust...don't breath this"
just watched a tv program the other day on the making of fluo tubes. the mercury gas inside is of such a low level that it 'barely' constitutes a health risk. the workers in the part of the manufacturing plant, after the gassing process don't have to wear masks.
Xellers (author)  mr monoply334 years ago
That's what the rubber tube and glue around the tube are supposed to prevent, but I understand what you are saying. I should probably post some sort of disclaimer.
yes, I do understand you were taking some precautions there, but your still working nearly unprotected until your finished, also, I'm not an expert with mercury, but it may also be able to diffuse thru the tube, but then again, mercury has a hard time working its way thru a colander, let alone intermolecular transport. So that wouldn't be much of a concern (at least I think) if it did break after it was finished, unless you waited a few months to get rid of it.
Xellers (author)  mr monoply334 years ago
No, I doubt that mercury could escape the tube unless it was damaged or broken (none of which have happened yet). Remember, these are used inside of scanners that are sold to consumers that use the in their homes. If mercury could escape the tube during normal operation, then the scanners would be recalled. In any case, just so you know, I don't really use this at all. It just sits safely on my bookshelf.
yes, I was saying if the bulb was damaged. And in a scanner it is pretty well protected...unless someone would step on the bed, I'm not arguing against you, this is a nice project that I have done my self, all I was saying was just watch while your handling this. you have applied the bulb in a much more portable and exposed application.
blahblah014 years ago
or you could use it to cold cathode mod a computer case, if someone else has suggested this bellow, sorry, i am too lazy to scroll down ;p
make a custom light saber lol thats coo
Luoma4 years ago
Read this and remembered I had one of those old things lying around, turned out great! Thanks for the guide.
Zqfgmb4 years ago
looks kinda like a lightsaber.
Xellers (author)  Zqfgmb4 years ago
Actually, if you disconnected the grounded high voltage lead from the tube, it would behave much like one of the model lightsabers that you often see.
panstar15 years ago
(removed by author or community request)
Xellers (author)  panstar15 years ago
Actually, in newer scanners, they make everything very specialized to the particular model and they make it all so small that you can't do this. They may even integrate the inverter onto the motherboard. That is why the best scanners for these lights are old trash ones.
12V Xellers5 years ago
they are also in lcd monitors 4each
wizodd5 years ago
Cold Cathode is a type of fluorescent, and they are used extensively in laptops, flat monitors, tv's etc.. Thus they are cheap. (And replacing one iin your monitor or laptop isn't as hard as you might think-nor expensive.) Directron.com & others carry them for case modifications for computer cases for about $5 including a 12v power converter. They are, like most fluorescents, quite efficient. They come in a bunch of colors and are often labeled "enon" which they are not. The ones sold for case mods are usually enclosed in an acrylic tube, which helps keep them from being broken.
Or you can use LED's if the CCFL's in your LCD burn out.
ubr.bzkr5 years ago
for the part where you said that if you connect the leads the wrong way you will destroy the power inverter, cant you just install a diode to prevent this from breaking it?
Xellers (author)  ubr.bzkr5 years ago
Of course.
use a bridge rectifier pos/neg to the lamp AC side to the power supply That way it doesn't matter which way round the DC supply is Zenderon :)
Coffee bean5 years ago
if you mount it in a PVC candle you have A LIGHTSABER!!!!!!
Angus065 years ago
Nice project, awesome pig.
sunny3425 years ago
what did you use to cover the light. plastic tubing.
Couple of questions.... 1. whats the wattage on these things? I made one today and it SEEMS happy on 12v 300ma, but I just want to make sure I don't burn my house down... 2. How strong is the actual bulb? is it going to burst into a million pieces if I touch it? 3. How long does it last? Days? Months? I have full intentions of making mine like a nightstand lamp... only solar powered if I can...
Xellers (author)  TheWelfareWarrior5 years ago
1) Sorry, I don't know the wattage, but you could probably figure it out if you look at a datasheet of the scanner that you extracted it from (assuming you extracted it from a scanner). But if your main concern is whether it will burn your house down, forget about it. 2) The "bulb" is made of glass and using it doesn't cuase it to heat up, so unless you exert some pressure (you drop it for example) on it, it won't break. 3) These lights should last you a very long time. LCD screens use these lights, so this could last you about as long as one of those. Also, the output from the power inverter should power almost anything that comes out of a scanner, so you can easily replace the "bulb" if it breaks. PS: Good luck w/. solar power! If you manage to make it work, please post another slideshow, or write something.
rc jedi5 years ago
nice, what can this lamp project be used for?
Xellers (author)  rc jedi5 years ago
The bottom of my description has some possible applications, but I just realized that if you were to build a source of 12VDC with the required amperage, you could use this in a camping tent. I'm gonna try that... But I'm also going to make another one and mount it inside of my PC. Hope this helps.
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