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Macro Photography Light Source Using Cold Cathode Lights

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Picture of Macro Photography Light Source Using Cold Cathode Lights
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

Picture of 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.

Step 3: Extract the LCD layer

Picture of Extract the LCD layer
Q2311022-CCFL.jpg
An LCD panel is made of three layers:
  • LCD - the black colored panel that actually produces images (upper most layer)
  • dispersion layers - there are usually three plastic layers that help disperse the light from the CCFL evenly over the entire panel
  • a reflective panel - the last layer of the panel - the CCFL bulb is usually embeded or attached to this layer. Use extreme care when handling this portion of the screen. The CCFL is very thin tube of glass that is quite delicate. Also, it is filled with mercury vapor which is not so good for you or your brain. Don't break it.

Remove any screws around the frame, and cut any tape from the sides of the frame. Remove any circuit boards from the back of the panel. Extract all three layers from the frame; separate the LCD screen from the other layers. Gently push all the remaining layers back into the frame and reinsert any screws. Set the LCD aside for some other project.

Sometimes the dispersion layers refuse to stay in the frame without the LCD layer in place. A small amount of clear packing tape around the edge of the frame will help solve this problem.

Step 4: Locate a DC-AC inverter

Picture of Locate a DC-AC inverter
The CCFL requires a fairly specialized circuit to drive it. LCD inverters can be found on EBay for about $12. Generic inverters will do the job just fine.

If you're salvaging a panel from a broken whole laptop or monitor, locate the small board that the panel plugs directly into.

If possible salvage the wire harness that is made for your inverter. You can remove the stock connector to provide bare wires that are easy to work with. The harness that connects to the DC in side of the inverter is most useful. Unless you have been extremely careless with the panel, the AC harness should still be connected to the CCFL tube.

In theory an inverter should be closely matched to the CCFL it will be used with. This will typically extend the life of the tube and board. This shouldn't be a problem for this type of project, however. As long as the inverter is for a tube of approximately the same size CCFL, it should work just fine.

Step 5: Create a Voltage Divider Circuit

Picture of Create a Voltage Divider Circuit
Unfortunately, most manufacturers refuse to release any information regarding their inverters. Some fiddling and testing is usually necessary to determine the input voltages on the inverter before it can be wired up for use. If you are using a complete LCD monitor, simply reassemble it, plug it in and turn it on and skip the rest of this instructable.

From my experimenting I've discovered that many inverters expect 12V+ input to drive the inverter and and around 5V+ to "enable" and set the "dimming" level. Check this generic spec sheet for some guidance: http://www.lcdinverter.co.uk/MH-1405A04-spec.htm. From my testing, the circuits are quite robust and can accept between 4.5 and 7 volts on the enable and dim pins and work properly. Above 7 volts a suspicious whining tends to be emitted.

A 12V DC power source can be easily adapted to power the inverter by using a voltage divider circuit. In a voltage divider circuit, use two resistors to drop the voltage as needed. In this circuit R1 drops the voltage 7V then R2 an additional 5V. Notice that 7V+5V=12V. The schematic below shows the circuit I used to create the voltages I needed to drive my inverter.

In this circuit, C is Ground, A is 12V+, B is 5V+. For an inverter that has enable and and dim pins, connect those to 5V+ to turn the screen on.

Prototype your circuit using a breadboard. Measure the voltage between C and A; it should be 12V+. Measure the Voltage between C and B and it should be 5V+. If you get values within 10-20%, you should be OK.

If you need assistance in choosing resistors for your particular voltage source, check out the Circuit Design Tutor.
Some tips to keep in mind:
  • If the sum of the ratio of the resistors equals the input voltage, your design will be much simpler. For example Vin=12V, ratio of resistors is 50:70 or 5:7 - 5+7=12.
  • Remember you can simply add resistors together in series to create a single resistor (read up on Ohms Law for help here.
  • If your input voltage is 18V, R1 should be 130K Ohm, R2 should be 50K Ohm.

E1: 12V source
A: 12V+
B: 5V+
C: 12V-
R1: 70K Ohm Resistor
R2: 50K Ohm Resistor
K1: SPST switch

Step 6: Test The Circuit

Picture of Test The Circuit
A word of warning here: The inverter creates extremely high voltage output. While it is rather low amperage, it can still do some damage. Don't even think about handling the inverter while it is on. Burns, shocks and maybe even death can occur.

Plug in your voltage divider, power source, inverter and panel and see if everything works. If your inverter is making a high pitched whining sound, it is either damaged or something is receiving too much voltage. Unplug everything quickly and double check your voltages and wiring. If voltages are correct and the whining continues, your inverter is most likely damaged. Find a replacement. Damaged inverters have been known to overheat and start small fires.

Step 7: Enclose the circuit

Picture of Enclose the circuit
Enclose the circuit - I like Ice Breaker Sours Gum boxes. They're super cheap, self sealing, easy to cut and just the right size for small projects.

Step 8: Complete and use the Light

Picture of Complete and use the Light
Q2311036-CCFL.jpg
Q2311031-CCFL.jpg
I salvaged my display from a non-functional laptop, so I had the advantage of having most of the parts I needed at my finger tips. I disassembled the notebook for parts and saved a few bits to complete my light.

I used the following parts to make a more complete light:
  • original screen housing with hinges
  • heat dissipation frame

I mounted the screen backwards on the frame using the existing mount points. This made a handy stand. I only had to counter weight the back to keep the screen from tipping over.

Step 9: Some Shots of the Light in Action

Picture of Some Shots of the Light in Action
Q2301015-paper_tape_forms.jpg
Q2311039-macro samples.jpg
Q2311040-macro samples.jpg
Q2311044-macro samples.jpg
These are some shots that I took using the light. The light was oriented to the right side of the light tent and was the sole source of light for most of the shots.

The shots have been post processed, but only for black/white balance and contrast.

Some Closing Thoughts
I'd like to get a panel with 2 CCFL tubes (top and bottom) and cut a hole in the center and use the panel as a ring flash.
ReCreate6 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)  ReCreate6 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 txoof6 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)  ReCreate6 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 txoof6 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 packrat7 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 packrat7 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 packrat7 years ago
With great care.
-henry-6 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-6 years ago
The LCD panel cuts out about 20-30% of the light. This is about recycling too :)
-henry- txoof6 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... %)
Myself7 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)  Myself7 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 txoof7 years ago
Why not extract the one in the panel you extracted from the laptop?
txoof (author)  ELF7 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 txoof7 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.
SurferGeek7 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)  SurferGeek7 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) 7 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!