Projection alarm clocks actually project the time on the ceiling over the bed, or onto the wall. Typically the sunrise alarm clocks that come with a plug-in power supply can project continuously, projection alarm clocks that are less expensive, project only when you push a button. The plus side of the continuous sun alarm clock is that when the room is dark, you can just look up and see the time.You don`t need to find the clock to push a button to illuminate the display.