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Macro Photography Light Source Using Cold Cathode Lights

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When shooting using a light tent a low intensity light source is quite useful. The CCFL (cold cathode fluorescent light) found in LCD screens is perfect for this purpose. CCFL and the associated light scattering panels can be found in broken laptop and lcd screens for virtually nothing.
This Instructable shows how to use the a salvaged panel, a DC power source and inverter to create a large, low intensity light.

Some Words Of Warning
This project involves electricity, high voltage and soldering. If you do not feel confident about working with any of these things, do not attempt this project.
 
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Step 1: Materials

You will need the following materials:
  • Broken LCD panel with a functioning Cold Cathode Fluorescent Light tube
  • DC-AC inverter for your LCD panel and hookup harness
  • DC power source capable of producing at least 12V
  • Soldering Iron
  • Selection of resistors (for a 12V power supply a 70K Ohm and 50K Ohm)
  • Single Pull, Single Throw switch (SPST)
  • Proto/Breadboard
  • Hookup Wire
  • Screwdrivers and other implements of destruction
  • COMMON SENSE FOR WORKING WITH HIGH VOLTAGE

Step 2: Locate a broken lcd panel

Locate an LCD screen that still faintly lights up, but is otherwise non-functional. If the screen does not light at all, it is most likely suffering from a worn out CCFL or inverter. In this case, you can try to purchase a replacement inverter or tube, but typically this is fairly expensive.

Broken LCD screens can be found on EBay. Look for 15"-17" monitors.
ReCreate5 years ago
Its ok,the "High voltage" is only 50 volts Really,I got shocked by this once and i am not dead.
txoof (author)  ReCreate5 years ago
Actually, the output of a CCFL inverter is typically between 120-2000V AC depending on the tube that it is intended to drive. It only takes about 60mA across the heart to induce fibrillation. That means only 60V AC, with sweaty hands (1,000 ohms resistance), is enough to cause some serious problems.

I have been careless and touched 120V household AC before and fortunately had no ill effects other than that horrible jerk and tingle sensation, but I'd rather not repeat it. The CCFL drivers are pretty safe, but should be handled with the respect and care that any electrical device deserves. It would be a long shot, but they could definitely kill you under the right conditions.

Check out this http://en.wikipedia.org/wiki/Electric_shock for more information regarding electric shock.
ReCreate txoof5 years ago
Umm...no to prove my theory,i connected a inverter from a 5 inch screen to a 13 inch,and it lights up perfectly fine Also,somewhere i saw that the voltage for backlights are about 48-49 Volts AC TRUE,It does use a massive amount of electricity to start the bulb,but thats for a very short amount of time,like a few Miliseconds
txoof (author)  ReCreate5 years ago
You are indeed correct that there is a voltage spike (strike voltage) when the light is initiated and the voltage does indeed drop during operation. This is due to the fact that a higher voltage is needed to kick start the the ions and produce the initial plasma that releases the photons that you see. Once the plasma is generated, the voltage drops back down.

The strike and operational voltages have to do with the size and construction of the tube as well as it's intended brightness. A lower voltage source can indeed drive a tube that it was not made for, but not necessarily to the specifications it was designed for. Also, because the gas in the tube heats up and becomes a more efficient conductor, the voltage should drop to extend the life of the inverter and tube. Using an inverter for a tube it was not designed for will not directly damage either, but can shorten their lives.

Check out this link for a sample of the operational voltages of common CCFL lamps: http://www.lcdparts.net/CCFL1.aspx

Check out the wikipedia page on CCFLs: http://en.wikipedia.org/wiki/Cold_cathode

A quick sample of CCFL voltages reveals the following:
  • Tube for 6.4" display - Strike: 1050V, Operational: 400V
  • Tube for 12.1" display - Strike: 1030V, Operational: 545V
  • Tube for 23" display - Strike: 2010V, Operational: 848V
ReCreate txoof5 years ago
sigh... no i connected my 14 inch CCFL to an inverter for a 6 inch and guess what,it lit up perfectly fine BUT whatever you win
You are totally missing what he is saying.
Congratulations my friend. Any other ancient comments you'd like to dig up?
Don't be dense. The concept of a "dead comment" at instructables is foolish at best
Especially if the thread is talking about a situation that might lead to death.
I don't mean to be rude, But in other words what i meant was: I don't care.
If the inverter and or ccfl from the laptop is euchred, you could use the inverter and or ccfl assembly from an old flatbed scanner. You could eschew the laptop panel entirely, and use the scanner's platen glass with a piece of paper or something, as a diffuser, although I'm not sure how well that would work.
txoof (author)  incorrigible packrat6 years ago
The paper would work OK as a diffuser, but the diffuser that is made to work with the light works extremely well. Think about how even the light is on a laptop screen. Good idea to swipe CCFL tubes from flatbed scanners tho; they're a dime a dozen at the thrift stores.
I agree that the lcd panel diffuser works dandily, I was just thinking that if one didn't have ready access to an old laptop, the paper and glass would be a cheaper substitute.
txoof (author)  incorrigible packrat6 years ago
Indeed, that would do the job. I think that a couple of white ladies' stockings might work better than the paper too.
Probably would work better. Now, how do we remove the stockings from those two white ladies?
Take them to dinner and a movie first. Don't rush the endgame. Unless your in college. Then just grab what you want.
txoof (author)  incorrigible packrat6 years ago
With great care.
-henry-5 years ago
Here's a simpler idea: Instead of removing the backlight, just turn the screen on high brightness and open some blank white file. just a suggestion
txoof (author)  -henry-5 years ago
The LCD panel cuts out about 20-30% of the light. This is about recycling too :)
-henry- txoof5 years ago
True, just a suggestion.
teddlesruss6 years ago
Scanner lights are definitely the go - the inverters are generally separate from the driver boards to save having to isolate circuits, they generally expect 12V as the power supply, and they run for ages. Get a piece of lucite or other clear plastic tube, slide in the CCFL and inverter circuit, seal with silicon, and you have a good 12V trouble light. I used one of these as a reading light for months, it still works but I've since bought a real reading lamp... %)
Myself6 years ago
When I initially saw the title of this instructable, I thought it was just another desk lamp made with a CCFL, and I was going to say "you know you can buy those premade now", but now that I see you used the diffuser panel too, I'm impressed!

I'm laughing because I've used my laptop's LCD as a diffuse light source before, just by displaying an all-white screen. Just shove the keyboard part under your light tent's base so you can get the light right up close to the subject. Hint: Use a paint program to flood-fill the screen with different colors, and it's like a lamp with adjustable filters! If you're feeling creative, display different patterns of color on the screen and watch the way the casts and shadows play on the subject. That could be its own instructable, actually.
txoof (author)  Myself6 years ago
That's how this all got started. I tried using my monitor, but the LCD panel was blocking a bit too much of the light (it only has around a 35-48% transmission rate). I'm thinking about buying a piece of polarized plastic (the kind they use in LCD displays) so I can have a polarized light source, which would offer all sorts of great possibilities. Thanks for the comments and the advice. I never thought about using different colors.
ELF txoof6 years ago
Why not extract the one in the panel you extracted from the laptop?
txoof (author)  ELF6 years ago
When the LCD is off, there is no signal coming into each of the pixels. The pixels scatter light in a random way rather than a polarized way. I would have to setup some sort of device that could send a signal for "white" to the screen to drive the pixels into the appropriate orientation. I'm sure this is possible, but I have no idea how to do it. Besides, I sort of wrecked the connector ribbon when I was pulling things apart ;) My simple solution is to use a piece of polarized film to do the job. I haven't yet purchased the film though. If anybody has a cheap source for quality, high transmission film, I'd love to hear about it.
ELF txoof6 years ago
Oh, but I meant disassembling the actual panel, to extract the 2 sheets of polarizing film inside them. If you're careful, and wera gloves so you don't get any of the crystals on your hands, there shouldn't be a problem. And most often you'd have to seriously damage the two thin pieces of glass between which the crystals are. Only problem I know of with this is that sometimes the manufacturer just glues the film onto the glass. Sometimes it's not the same piece of glass that's holding the crystals, but sometimes it is (usually small screens, like PDA's and other compact units have it all glued together) I bought 3x A4-sized sheets for about $40 including shipping (to Denmark). Should I dig up the web-site for you? Took them 4 days to deliver, and that was in the christmas holiday...
Great instructable and simply beautiful photos.
SurferGeek6 years ago
I like the idea of reusing a LCD you might have lying around but in the long run it would be cheaper buying a couple of CFL. One LCD "light panel" only gives you light from one side.
txoof (author)  SurferGeek6 years ago
Indeed, the light does only come from one side, but it's not a problem. The light tent helps scatter the incident light. Using just a bare CCFL won't provide the same even light that the scattering layers provide. The fact that it is low intensity helps eliminate harsh shadows. A second panel from the other side would definitely help with any shadows.
Make sure you check out the $10 macro photo studio on Strobist.
I'm also thinking about finding a 2 CCFL panel (top and bottom) and cutting a hole dead center to make a crude ring flash. Problem here is how to mount the thing to the camera without breaking stuff.
Also, check out used computer shops, or computer repair shops. They typically have a few panels laying around that they'll give away.
txoof (author) 6 years ago
I'm really pleased with the results. The CCFL works great because the light is already white balanced.

Be sure you (or your friend) check out the $10 photo studio over at Strobist. It's basically the same thing that I use, but home made.
Awesome!!!! Seriously, this is super cool, I might show this too my friend because she is really good at photography, and photoshop and stuff, she might like this, thanks!