Monday, August 25, 2014

Repurposing a Laptop screen as a Universal Test Display Rig


Although I am fairly well set up for working with multiple computers on a single monitor (using a 4 channel KVM switch), from time to time I have an extra equipment, be it a PC, laptop, or any other consumer electronic device that needs a display to interact with it, that is always a pain to hook up with a monitor or TV for trouble shooting. As I recently had success experimenting with LCD panels salvaged from old laptops/TVs, I decided to make a permanent test rig for such occasions.
Finished look

Materials and tools used

As the base of the whole assembly, I used a sheet of hard paper that once was the back panel of an IKEA picture frame:
  • It's just the right size: The LCD panel and driver/controller boards I had lying around just fit on it nicely.
  • Strong enough to hold itself and all the parts I had in mind, but, at the same time, it's very easy to work with - After all, it's made of paper.
  • Cheap: I had it as a leftover part from one of my Digital Picture Frame projects. So I won't get too mad if I mess up something.
For stand-offs and screws (to hold the driver/controller boards in place) I used some bits and pieces from the library of PC case screws, etc. I have accumulated over the years building countless PCs.

3mm copper stand-offs
To hold the LCD panel in place I used some self adhesive Velcro strips. The advantage of this is that I can easily replace the LCD panel if needed.

Apart from these materials I used a Dremel to pre-drill the holes for the stand-offs.

Assembly steps

I started by laying down the components on the base in a way I thought was practical.

Then I attached two Velcro strips to the top and bottom, i.e. long edges of the back of the LCD panel:

A close-up of one of the Velcro strips attached to the back of the LCD panel.

Next I removed the protecting tape from the Velcro strips (on the LCD panel) and I simply placed the LCD panel on the paper base. This will ensure that the receiving Velcro strips will be perfectly aligned with the mobile ones.

Velcro strips firmly in place. Also, the location of the stand-offs marked.
With a pencil or felt tip pen I marked the spots for the holes to be drilled for the stand-offs. I pre-drilled the holes a bit with a Dremel then I screwed in all the stand-offs:

All stand-offs in place.

Of the three PCBs I mounted the display driver PCB first, as it had the most "dependencies": cables, stand-offs, etc.
LCD driver board firmly in place.

Next came the high voltage (or inverter) PCB. The LCD panel has a very short lead for the inverter connector, so this PCB had to be mounted very close to the LCD panel:

Inverter right under the LCD panel.

Last one was the user interface panel - this one has the on/off LED, as well as the buttons to manipulate the OSD menu:
This control panel is now in the lower left corner of the assembly.

Assembly: DONE!

All three PCBs mounted in their places.


Since I used an LCD driver board that has HDMI, composite video, RGB monitor inputs, I now have a test rig that is able to display almost any kind of video source I throw at it. In the below example I am using it for the initial configuration of a headless Raspberry PI system:

It works!