The SNTP synchronised clock (ssc) is an ESP8266 based time of day clock with an LED display.
Above are two prototypes both using HT16K33 display modules. (The display has a blinking colon, it is off in the pic.) There is a silicon photo transistor just above the display, used to sense day/night and the firmware changes display brightness.
The upper switch is used to select daylight saving mode, and the lower switch selects MM:SS display which is convenient when setting other clocks, watches etc.
Design criteria
The design criteria are:
- small, portable, powered from a 5V USB power supply;
- synchronised to an SNPT (simple network time protocol) server;
- flexibility for a range of displays (74HC595 static, TM1637, HT16K33);
- support display brightness adjustment with night / day detection;
- configurable time zone offset and daylight saving offset;
- configurable from a web page;
- switchable HH:MM and MM:SS display formats (for convenience in setting other clocks, watches etc); and
- switchable daylight saving mode with configurable offset.
The concept is that it is synchronised to net time, and the only adjustment needed through the year is to flick the switch the daylight saving mode.
The hardware comprises:
- ESP8266 dev board of some kind;
- 5V to 3.3V power supply; and
- 4 digit 7 segment LED display, preferably with a colon in the middle.
Above is a development prototype using a Wemos D1 mini ESP8266 board and 4 digit display using 74HC595 shift registers.
The HT16K33 is a better display option, it has a colon, and it supports variable brightness.
WiFi settings and key system parameters are entered through a web page obtained from the on-board web server.
Boxing it up
The prototypes were housed in ABS Jiffy boxes with a custom front panel cut from 3mm red acrylic sheet. Design was done in Freecad, manufacture on a DIY CNC router.
The layout is drawn up in a sketch with constraints to suit the design.
Above, the feeds and speeds calc.
Above, the larger display unit, cut with a 1.6mm carbide end mill.
Above, the smaller display unit.
A work in progress…