Clock16

This project presents digital 24 hours clock. While having only sixteen LEDs it shows time with 15 seconds precision. Some additional info regarding this project motivation you can find in this blog post

How to Read the Time. WEB Model

Here is web model which helps to understand project interface. You can work with model by clicking this link: half-dial-web-model If you don't like clicking unknown link you may deploy the model locally. Just clone this repository, go to the directory p5model, and open index.html file with browser of your choice. Model has four clocks. They all synchronized and show the same time.

1. First clock at the left is the regular analogous clock. Nothing to comment here.
2. Second clock works similarly to the first, apart of the fact that in place of clock hands there are circular arches. Normally clock shows time by angles between vertical axis and hands . This arch clock shows time by angles occupied by arches (outer arch for minutes, inner arch for hours ). Arches start at twelve mark and grows clockwise.
3. Third clock has arches as well but instead of clock dial there is only half-dial. For hours less than six and minutes less than thirty reading the time is not different of the previous clock. Arches start at twelve mark and grows clockwise. But when hours are in the range 6..12 or minutes are in the range 30..60 there is the change. Hands of the regular clock under these conditions are positioned at the left side of dial. But for this arch clock there is no left side. Arches occupies the same right side but starting point and direction how arches grow change. Under these conditions arches start not at the twelve mark but at the six mark and they grow counter-clockwise. That way clock show hours from 6 till 12 and minutes from 30 till 60.
4. Fourth clock is similar to the third but arches are dotted not solid. This clock does not need dial marks: dots itself are marks. White dots of inner half-dial shows hours, green dots of outer arch show time with five minutes precision. Additional one minute precision achieved by a color of the last dot of minute arch. Depending on color of the last lighted dot add value to the time provided by green dots (for cyan add +1, for purple add +2, for red add +3, and for blue add +4 ). This last clock model is very close to the real LED based clock (just substitute dot with LED).

Model allows to play with clocks dynamically. Three modes exist:

1. Manual mode. Top slider allows to change clock setting.
2. Real time mode. Clock shows current local time on the machine where browser is running.
3. Simulated mode. Time change is simulated (bottom slider allows to increase or decrease simulation speed).

Real LED clock is different of dot half-dial model by having two more LEDs.

1. Central LEDs changes color each 15 seconds. When clock is in set mode this LED is dark.
2. LED on the left part of the clock. It is PM LED. This LED is off when time is in the range 12 AM ... 12 PM. Otherwise it is on.

Components and Circuit

Here is list of project components.

1. Atmega328p Microchip processor
2. Five 10mm tri-color common cathod LEDs
3. Three 10mm tri0color common anod LEDs
4. Seven 10mm white LEDs
5. 5mm white LED
6. Sixteen 75 Ohm/0.125 W resistors
7. Eleven silicon diodes 1N4148
8. Schottky diode 1N5817
9. Three micro buttons
10. Super Capacitor 0.5 MF 5.5 V
11. Power down supply LM2596
12. Crystal 32768 KHZ
13. Opto-pair NTE3042
14. Resistor 220 Ohm/ 0.125 W

Each multi-color LED consists of three color LEDs, so overall there are 32 LEDs. Single pin in this circuit controls two LEDs.
Circuit has power down supply, which converts 5V power to ~4 v. It is needed to avoid weak LED lighting when chip pin takes in-no-pull-up mode (program set it when LED should be off). Super-capacitor and Schottky diode allows to keep clock running in case of occasional power loss. Opto-pair delivers signal of the power loss to the microchip and program may switch all LEDs off to prolong clock work while power is down.

Program

To program device I used Microchip Studio. Program written in C language and complied by XC8 compiler. AVRISPII interface device allows to upload compiled code to the microprocessor memory.