Doomsday Clock Shield Kit for Arduino by Samurai Circuits Six, 7-segment LEDs with Decimals and clock colons. Need we say more! Useful for displaying the date or the time Year-Month-Day (yy-mm-dd) or Hour-Minutes-Seconds (hh-mm-ss) One 4 kHz beeper, with the beeper you can add a chirp to every second that passes increasing the sense of urgency of your countdown. Or you can use it as an alarm at the end of your countdown. 12 Indicator LEDs, There are 12 LEDs across the top that can be used for indicating a variety of things. For instance As a visual indicator like a speedometer or level indicator. Or you can label the LEDs and have them eliminate represent different modes or functions. Photo Resistor, You can use it as an experimental input and display the analog output value on the LED display. Or if you are trying to design the perfect alarm clock, you can use the photo resistor to detect the amount of ambient light and have your alarm clock display at full brightness during the daytime and appropriately dim the display at night. Rotary Encoder, The rotary encoder is an optional add-on. It can be potentially used for setting the time or for the length of your countdown. Rotary encoders are arguably better than potentiometers. Rotary encoders can be turned a limitless number of times. Whereas potentiometers its often less than a full revolution. This particular Rotary encoder also has a built-in button. So you can turn it or push it.