Advanced Member level 4
Presented here design is a simple clock based on seven-segment displays, which can be easily made at home by every beginner within 2-3 hours. This device can be a nice gift made by yourself.
Schematic and some useful pictures can be found HERE.
The clock uses quartz 32,768kHz. There are no noticeable errors in counting the time – in a week it delays by approximately 1 second in comparison to DCF. Driver and display boards are designed so that put together they form something like a “sandwich”. Driver was based on Atmega8L. In case of power failure, the clock switches off the display, only diodes between hours and minutes keep lighting. Atmega8L works from 3,3V, so a package of 4,8V accumulators with a capacity of 1000mAh lasts for few tens of hours of operation without the current. The circuit then takes 8mA and the LED consume great amount of power. Processor takes less than 1mA. During normal operation, current consumption is within 32 and 38mA.
Between digits there are comma diodes blinking with a frequency of 1Hz.
Front panel was cut and engraved in black plexiglass using a laser. All was closed in a housing made of aluminum sheet, floor panels and plexiglass (when you use plexiglass dimmed red, it would work as some kind of a filter, which provides far better visibility of digits.
- electronic elements
Link to original thread - Zegarek na wyświetlaczach 7-segmentowych.