Chosen Solution

Hi to all electronic wizards, my 11" 2011 Macbook Air display seemed cracked and had sort of a color bleeding growing from the crack, making it unusable. I swapped it with a new display using a great iFixit guide, so the computer is good as new. The old display still has nice, even, white light (except from where the crack is, of course), and I thought it could be reused as a small slide sorter, as I have a project coming up where I will be sorting a couple of thousand slides, scanning the best ones. Does anyone know if it is possible to light the LED backlight of the display without it being connected to a motherboard, for example just by supplying current to the right wires? I have little knowledge of electronics, but have soldered before and I think there is very little to loose here, anyway. I was hoping someone could suggest a solution, or eventually tell me if this is totally hopeless. All the best!

  • Ivar I can’t align the text with the images, but they show:
  • Overview
  • LVDS cable, motherboard end (2 pics)
  • LVDS cable and connector on circuit board in the screen
  • Flat cable from LED strip
  • Connector for LED strip cable

Ivar O, yes it absolutely is. I do that with old CCFL panels. Those make great reading lights:-) In order to get it accomplished we will need to at least have the number for the panel. I am certain that your will have an LCD backlight, so your power demands will be a lot less than the CCFL monitors. Post a couple images of your panel so we can see the wiring as well. UPDATE Okay so your LED driver is a LP8550 with these brief specs: High-voltage DC/DC boost converter with integrated FET with four switching frequency options: 156/312/625/1250 kHz 2.7V – 22V input voltage range to support 1x…5x cell Li-Ion batteries Programmable PWM resolution -8 to 13 true bit (steady state) -Additional 1 to 3 bits using dithering during brightness changes I 2C and PWM brightness control Automatic PWM & current dimming for improved efficiency PWM output frequency and LED current set through resistors Optional synchronization to display VSYNC signal 6 LED outputs with LED fault (short/open) detection Low input voltage, over-temperature, over-current detection and shutdown Minimum number of external components Micro SMD-25 package, 2.466 x 2.466 x 0.6 mm This will help us to determine what voltage you need for the input. Further parameters of this IC are : Vin (Min) (V) 5.5V Vin (Max) (V) 22 Vout (Max) (V) 40 Iout (Max) (A) 400 Shutdown Current (Typ) (uA) 1 Iq (Typ) (mA) 4 LED (#) 60 LED Configuration series LED Current Per Channel (mA) 30 Here is one way to build a driver circuit for your LED backlight

Next is an image of your LCD connector. Pin 6-11 are the backlight connections

This is where the importance of your LVDS cable comes in handy. You can now either traces the wires from your connector to the panel, or use the connector and purchase the female part that is usually on the logicboard, to build your driver. the connectors are available at places like this as well as many others So, again, you could use the IC typical application, or you could emulate the backlight driver circuit that your computer uses. Here is the schematic for that.

There is another thing you could do. That is to get a commercially available DC-DC converter that is capable of producing the proper voltages. Those are pretty much available at ebay.com as well as many other places. Then connect that to your panel using the pins as specified. This is definitely a great project to continue to use old LCD panels. Hope this helps, good luck.

How come the LCD connector here is 40 pins, when I have count only 30 pins ??