The idea

The first time I saw a projection clock (a friend had shown me his projection clock, which he used to project the time on his bedroom ceiling), I knew I could easily build my own by converting a watch with an LCD display.

I bought a very very ugly watch in a dollar store. So ugly that it really is unwatchable ;) At least it's easy to disassemble...

Disassembling the watch

To remove the pcb, just remove the screws:

The LCD is mounted over the PCB. A conductive rubber bands holds the pcb in place and conducts electricity between the LCD and the PCB. Just pull on the LCD and it will come off easily.

White on black LCD

The LCD is not usable as-is. To be usable, (1) light has to be able to pass through it and (2) the display has to be black on white (transparent on opaque).

Remove the reflecting background sticker to let the light pass through the LCD:


To get a transparent-on-opaque display, reverse the polarizing filter located on the LCD front side:


See the difference? Left picture: before, Right picure: after.


For more information on LCD technology, read the Wikipedia LCD page.

Reinstalling the LCD

In order to prevent the PCB from blocking the light, I extended the contacts on the PCB with small pieces of wire:


A sufficient pressure must be applied to obtain a good contact between the wires and the conductive rubber band. Otherwise, some segments may not work correctly:

Buttons

In order to be able to set the time easily, I installed two buttons on a small PCB. Next, I connected the wires on the watch PCB where the original buttons used to be:

Light and lens

I use two high intensity white leds as a backlight. The backlight has to be very bright. A magnifier is used to focus the light on the wall. The focus is adjusted by moving the magnifier.


Here is how the LCD must be oriented if you want the time to be projected in the correct orientation:

Pictures

My clock is not very nice to look at, but at least is works. It is build from various pieces of hardware glued together with hot glue.

The clock in action, projecting the time on my lab wall:

The clock in darkness: