Digital Clock w/ 6 Digit Kit with Countdown, StopWatch and Alarm

Features

There is also an output tied to the piezo that can be interfaced with other microcontrollers if you want to use the alarm or countdown timer function to alert an external MCU. The video above shows you how to set the functions, and also acts to show you how to put it together. link below that shows you the schematic of the device.

• Power Supply: 7VDC - 9VDC (regulated to 5VDC on the board). Although schematic suggests 12, don't use higher than 9V or the regulator will get hot.
• A custom PCB and all the parts required for a complete build.
• 4 Settings: CLOCK/ALARM/COUNT DOWN/STOP WATCH
• External alarm output for easy interface with another MCU.

Assembly and Demo

Useful Modifications

dipmicro suggested TO220 regulator (not included) since the TO92 is getting too hot above 10V input and Patrick tells me he has hundreds of the kits at the moment, so there will be some time before kit revision. However, he put together a video showing how can you modify the kit yourself.

Secodly, keep in mind that LED segments are responsible for most of current into the unit, so if you decrease brightness enough, you may somewhat increase input voltage without modding to TO220 regulator. The 78L05 cannot get too hot and current cannot go over 100mA.

The following modifications use parts that are not included in the kit and need to be acquired separately.

• 1) Replace 78L05 with 7805
• 2) Replace Colon LED resistor (R7/R8) with 10k ohm resistors
• 3) Replace 7-segment display resistors (R1/2/3/4/5/10/11) with 2k Ohm resistors.

Schematic

Click image to zoom.