Thanks for the responses, I'm probably not explaining exactly what I'm trying to do very well. Yeah I'm aware of the basics of how LCD displays work, each pixel is comprised of three liquid crystal cells that twist the polarised light from the back layer such that it passes through the front layer and color filter polarised at 90° to the back layer. The light source doesn't really matter as the projects I have in mind use light passing through the panel in other ways, I just want to know how to supply whatever signal I need directly to the cells to manipulate the liquid crystals for all of the red cells, blue cells and green cells as groups to pass light through the panel in a range of colors. For example, if all of the cells have a positive and a negative (just for examples sake) I want to tie all of the positives together, and all of the negatives together for all of the red cells and manipulate them together as a single color filter for the whole panel, and the same for blue and green, to pass light through in whatever color I need. Its not only for display purposes but also for light color filtering for other projects.
I'm certain this can be done, but would require some in-depth knowledge of the panel you are going to be using.
Because of the sheer number of pixels in a display, they will be multiplexed... if you want to treat the display as one giant pixel, they don't really need to be multiplexed any more. With that said, I do not have the experience required to tell you what you will need to directly control an LCD sub-pixel. This could be complicated further by running more than one cell in parallel.
To take on this task, I would encourage you to grab a multi-meter, and oscilloscope and begin poking and prodding the control board.
I'm certain you will have better luck 'hi-jacking' the control board to trick it into displaying one color than to bypass it and attempt to drive all of the cells yourself.
I would still very much like to encourage learning and using a display communication standard... some very basic VGA code can be transmitted to send all red, or all green (or any variation) to the display. The on-board driver will worry about all the other details.
*Note that even when buying an LCD screen for projects or development, it is rare that the cells are directly driven. You are usually presented with a driver that accepts a specific or set of specific communication protocols.
This is like trying to build your own control unit for a car engine. Sure it can be done, and lots of people have done so, but unless you want to invest that kind of time into it, it's simpler to use an existing ECU and simply push the gas peddle down with a solenoid.
I wish you the best of luck on your project, and hope that when you crack apart a display to attempt this on that you do your best to keep the drivers in good condition just in case you run into a road block.
Some questions you will need answered to drive the display your way.
- Are all the sub-pixels in the display connected in a common cathode or anode setup? (This makes multi-plexing incredibly easy... but there are alternative driving methods like
charlieplexing which could make your proposed solution a huge hassle)
- Are the sub-pixels supposed to be voltage or current driven? (If you are unsure on the differences... you should visit the '
How to drive an LED' resource. You could easily damage a cell, a row or cells, or a group by driving them incorrectly)
- What are the specifications at which I should drive the cells at? (Regardless of driving method, there will be a specific rating that should not be exceeded)
- Are the sub-pixel intensities directly proportional to the control voltage/current or PWM %? If you want 30% green, will you need to build a circuit to compensate for any non-linear responses? (Commonly, running something at 50% does not always appear to be running at half-brightness, or half-volume.)