Introduction: LED Backlight for an LCD Monitor or Television
Finalist in the
Back to School Contest
Non-working LCD screens can often be found cheap or free. I started doing this originally because I needed multiple screens for schoolwork but didn't want to fork out the money for a brand new one. The key to getting a suitable one for this Instructable is to get one where the screen itself is not broken. This Instructable will describe how I replaced the CCFL (Cold Cathode Fluorescent Lamp) backlights with LED strips. The advantage to using these instead of single LEDs is that the LED strips can be purchased cheaply on Ebay and the monitor can be completely reassembled because the LED strips take up less space than the original CCFL backlights. This means that externally the modified screen will look just like a stock screen.
From my experience, these non-working screens usually have problems with either the power supplies or the inverters for the backlights. Often times, these problems are easily fixed by replacing bad capacitors, but occasionally the problems are different. I managed to accumulate several screens with problems with the inverters I was unable to diagnose with a reasonable amount of effort, so I decided to replace the backlights with LEDs, thereby cutting out the faulty inverter circuit.
DISCLAIMER: This instructable involves opening and modifying electrical devices and handling bulbs that contain mercury. It is meant to be a recollection of the process I used to modify my personal monitor, not a step by step guide for all monitors. Do not attempt this Instructable unless you are qualified to do so. Be sure you are comfortable and qualified before attempting any Instructable and be sure to always disconnect power before working. I cannot be held responsible for anything that comes about from attempting to replicate this Instructable. Attempt it solely at your own risk.
Step 1: Tools and Parts
To complete this project, I used the following tools and parts.
Self Adhesive Surface Mount LED Strip
Step 2: Disassemble Your Screen
I will not try to explain how I opened my screens because each one varies so much. The biggest thing was to make sure I could put the screen back together once I was done. Basically though, I needed to open the outer plastic case which is usually held together by screws and snaps first. Next, I usually needed to remove a metal cover on the back of the newly exposed inside of the screen. This should expose all of the circuit boards, so I could now unplug the CCFLs from the inverter board. I needed to continue this disassembling until I could remove the metal holders containing the CCFLs. In all of my screens, there is one on the top of the screen and one on the bottom.
CAUTION: By disassembling my screen this far, I exposed the very fragile parts. I used extreme caution to avoid breaking anything.
Step 3: Dispose of the CCFLs
Next, I needed to carefully remove the CCFLs from the metal holders. I needed to be extremely careful because each of the lamps contained mercury. This also meant I needed to dispose of them properly and responsibly.
Step 4: Add LEDs
Now that the CCFLs have been removed, I could cut an LED strip to as long as possible where it still fits in the metal holder from the CCFLs. I then needed to solder wires to the positive and negative terminals of the LED strip. Then, I peeled off the backing and stuck the LED strip in the metal holder with the LEDs pointing towards the screen. The wires should exit the same side of the screen as the original wires from the CCFLs. See the picture for more details.
Step 5: Reassemble Your Screen
Now, I could reassemble my screen with the metal CCFL holders in their original place, but now containing LED strips instead. I had to be sure to take my time and carefully assemble the screen correctly. Also, be sure to route the wires from the LED strips in the same way as the wires from the original CCFLs. Do not go so far as to cover up the circuit boards yet.
Step 6: Remove Inverter Board and Connect LEDs
Now that I have replaced the CCFLs, I can remove the inverter board as long as it is completely separate from everything else. My LED strip runs off of 12VDC, so I had to find a source and neutral point to solder the wires to. From my experience, this is a very common voltage in LCDs, but make sure to find a 12V source that is off when the screen is off and on when the screen is on or else the LED strips will always be turned on while the screen is plugged in. Also, make sure it is capable of supplying the necessary current for the LEDs needs. I wanted to use a fuse on the 12V line to be safe. Once I attached my wires, I needed to secure them so they don't move around or get pinched during the final reassembly. I could now continue to reassemble the screen until it is completely put back together.
Step 7: Test and Enjoy
If I connected everything correctly, I should now be able plug the screen back in. When I turn it on, I noticed that it is slightly dimmer than a regular screen depending on the LEDs used. Also, depending on how far apart the LEDs are on your strip, I noticed some slightly bright spots near the edges where the strips are placed.
I have not noticed any significant bright spots, but have noticed the screens are a bit dimmer than an unmodified one. It is especially apparent when the screen size gets above 19 inches. Also, the dimming function no longer does anything. While it may not look quite as good as an unmodified screen, a screen with LED backlights is more than acceptable when I realized the only part I had to pay for was probably the LEDs. If I used better LEDs than I did, I could probably make a screen that looks better than the original.
I tried to get a picture of the bright spots. These pictures were taken at an angle towards the LEDs with a solid white screen displaying. The screen looks much better from straight on and with something other than a solid white screen.
We have a be nice policy.
Please be positive and constructive.