Here is something that will definitely catch the attention of your guests, although the project’s author wasn’t lucky enough with the WAF (Wife Acceptance Factor). A laser beam showing the time on one of your walls, an unusual clock indeed and very easy to build.
Tracking the time is done by an Atmel Attiny24 microcontroller. It feeds a PWM signal to a servo motor that rotates the laser. The laser, controlled by the Atmel and driven by a npn transistor, can be set as a continuous line or pulsating. A crystal oscillator is used for best accuracy. Connector J1 is used to set the time and for settings, using a jumper. It can be set to show hours or seconds for example. Of course you could replace this with push buttons and/or switches.
It’s best to adjust time at fixed hours otherwise you will have to count seconds to adjust minutes. Also depending on the type of servo motor you will be using you might need to play with the values of servo’s rotation span. There is a version available using the Arduino.
The code is written in C and it is very well commented and that comes in very handy if you want to add some modifications. There are some things you will have to look out for when recompiling. Circuit diagram and code are available in the project as well as pictures and a video of the sundial.
Laser Sundial: [Link]