I disassembled a cheap "wall projection" clock:
As a small hobby project, I'd like to wire this LCD up to a Wifi-equipped Arduino and make a simple NTP-based projection clock.
How do I interface with this board? I've never directly interfaced with an LCD before (with no accompanying control circuit), so I'm not sure how to proceed. As the image shows, the LCD board has two small ribbon cables containing 6 wires each. On each cable, one of the wires has white insulation. All 12 wires appear to go directly into the LCD pane, with no additional discrete components on the board.
The clock was powered by two AA batteries, so I'm assuming the logic level it uses is no more than 3V. The projected image displays the standard 4 clock digits in the format "24:59".
How do I apply voltages to these wires to display digits? Is it a simple one-to-one interface, where energizing one wire causes part of the display to turn opaque, or is it some sort of matrix, where multiple wires have to be activated in sequence to form the overall digits? Is it safe to assume the white wire is ground and the grey ones are signal, or is it the opposite?
Since I only have one of these, I don't want to blindly start experimenting by applying voltages across wires, and risk destroying it. How should I proceed?
Edit: I checked the output of some of the LCD pins from the clock's original control board and the patterns look very similar to the "multiplexed" example shown here. Each pin is outputting up to 4 logic levels. So I think I can safely assume it's a multiplexed LCD. Since I have 4 digits, does that mean there are 4 common/back plane pins? How would I generate 4 logic levels from an Arduino? Do I need to generate 4, or can I get by with two using the LCD driving method described here?
Edit: I'm pretty sure this is the output from one of the backplane pins, since it never changes, even after several hours. It looks like the pulse is 4ms wide, for a total "on" phase of 8ms, and the distance between repetitions is about 16ms. Based on the documentation for multiplexed LCD control signals, the pulses on the backplane pins can't overlap, meaning there's only enough room in the "off" phase for one other backplane signal. I think that implies there are only 2 backplane pins. Is this correct?