Do you have an old laptop of tablet that does not work anymore? You may have a practical and useful monitor before putting it in the recycle bin. We will see how we can extract the LCD panel and transform it to a portable monitor that we can use it as an additional monitor, or entertainment display for the car, or as the front end in the next IoT project.
Panel Disassembly
The first step is to disassembly the old device and extract the panel. In this step you can visit the youtube for finding the appropriate way to extract the panel in few minutes. After extracting the panel we have to identify the to major connections: the backlight connection and the LVDS connection used for transmitting data to LCD.
Old fashioned displays usually using CCFL type lighting source for the back-light. This type includes a cold cathod fluorescent tube that requires a high voltage power supply. Disadvantages of this type are: the limited life of the CCFL tube, the cost – mainly due to expensive part used in the high voltage power supply, the non uniform light and the high power consumption. Most recent displays are using LED light. LEDs are using low voltage, are more efficient and have increased life.
There are many LVDS interface variants, using different connector type or number of LVDS signals. We do not have to worry about the LVDS details. Having the LCD part number we can directly search for a compatible controller.
Finding the appropriate controller
Having all the necessary information we may now search to find the required parts in order to build the new monitor. The controller is the part that receives the video signal from the source – ie from our PC – and transforming it to LVDS differential serial interface that the LCD panel needs. The part number of the monitor, the LVDS connector type the pin count, the resolution, the backlight connector and type are the main characteristics that will help us to identify the right controller.
First we have to find a controller supporting the same connector. In example having a flat cable connector – for supporting flat cable monitors – or pin header for supporting cable assemblies. Then we have to look for the LCD pinout information in the data-sheets. LCD Datasheets provide information about the signals that should be connected in each pin. Signal may be the power supply, the LVDS channels (LVDS channels are depend on the LCD model), the LED background input or any additional control pin.
In case of flat cable we should be sure that the signals on the controller are the same wit the signals on the LCD – or otherwise we may have to use the appropriate adapter. In case of pin header connector we should find or build the correct cable for driving all the necessary signals. Usually, we can contact the controller supplier and ask for providing the appropriate adapter or cable harness for our display.
The controller has to be configured in the appropriate resolution that the display is capable to work. Depending the controller there are many different ways to do this step. Some common options are: from the OSD menu, using jumpers on the board (following picture) or even using a special programming port. The most common way to make sure that we will not need any additional equipment and everything would be ok, is to communicate the LCD part number to the controller supplier. Usually suppliers have all the necessary equipment and knowledge and can do the job before shipping the controller.
In case of LED back-light, most small-medium size displays provide the necessary voltage from the same hardness. If not we my need a small voltage regulator or just a resistor (driven from the DC supply) for supplying the LED. In case of CCFL displays, we will need a high voltage supply. Some controllers have already the high voltage supply embedded – if not we should be sure that the power supply is included – in the controller package – or buy an extra power supply.
The last and most common part that we will need, is the power supply. We can use a common power pack on the rating controller voltage (usually 5V or 12V) and enough amperage – depending on the display size and the back-light type (usually 2A are enough for most 8″ to 15″ panels).
Testing our new monitor
Now we may have our final test. We need to connect the controller with the panel, the back-light supply, feed the controller with the input signal from our desktop and finally the supply the DC input of the controller.
The above image displays an old tablet 8″ display, connected on a VS-TY2662-V1 (PCB800099) controller. VS-TY2662-V1 is an common, low cost, LCD controller that can be programmed to support most of the mid-size LCD displays. Based on RTD2662 chipset from RealTek, the board can be programmed and configured for our application. The board is supporting HDMI, VGA and Analog Video inputs.
Find the new case
The last step is to find the appropriate case that will accommodate the new monitor. The options are unlimited, we may cut a plastic frame, a wooden frame is also an option or we can use the original holder used in our laptop by extracting the whole monitor frame from the old device.
What else?
So, having our next-project monitor ready, we may also add a touch screen. We can have a resistive touch panel for few dollars – including the USB controller. The only think that we should know is the panel diagonal size and the ratio. USB touch panel controllers are very common and are detected from most operating systems (including Windows and Linux) with out any problem.
Good luck and don’t forget to send us photos from your experiments!!!