Tuesday, February 24, 2015

WiFiChron clock kit now available

Update Sep 18, 2017: Here is the latest revision of the PCB included in the kit.

Update Oct 8, 2015: The latest revision of the PCB (pictured here and here) has hardware support for XBee (which also covers GPSBee, WiFiBee and BTBee).

With this kit you build a clock like the one shown in the photos below.



There are two buying options:

1. use or make your own enclosure

 (US$47, free shipping to North America)


2. enclosure included (Serpac A20, transparent front panel, screws, back panel hand-drilled with 3 holes for buttons and rectangular opening for the USB connector)


 (US$61, free shipping to North America)

The kit includes the following electronic parts:


  • main PCB
  • display adapter PCB
  • ATmega328 with 8MHz bootloader, programmed with a clock sketch + 28-pin socket
  • 74HC595 shift register + 16-pin socket
  • HDSP-2534 8-character alphanumeric display + 4 x 6-pin machined headers
  • DS3231 + battery holder + CR1220 coin battery
  • LM1117 3V3 regulator
  • 3 x right angle push button
  • 5 x100nF capacitor
  • 3 x 10k resistor
  • 220uF (or so) electrolitic capacitor
  • 2 x 12-pin right angle male header
  • miniB USB connector
  • buzzer
Schematic and board layout are shown below.



The board supports other types of displays as well, through the use of adapters. So far, beside the HDSP-2534 coming with the kit, there are adapters for HDSP-231x and QDSP-6064 (the sketch is different for this one), shown below.



Assembling the kit

Finding the right place for the components on the board should be straightforward, since the silkscreen shows their values and their orientation.
It is very important to pay attention to a few aspects:
  • the orientation of the DS3231: the key (pin 1) must be the top-right on the board (so that you'll see the marking on the chip upside-down);
  • solder the USB mini-B connector BEFORE the capacitors surrounding it, or otherwise you'll be forced to solder the USB's ground and Vcc pins (the 2 extreme pins among the 5) in a very cramped space;
The procedure to attach the display is as follows:
  • first insert the little adapter PCB all the way into the right-angle headers, then the headers themselves into the main PCB; solder the headers to the main board first, making sure that the small PCB adapter is perpendicular on the main board;
  • solder the display adapter PCB to the male headers, after it's inserted all the way, with the so the headers' pins stick out;
  • cut the sticking pins to the PCB level; at this point you have the adapter attached and connected (perpendicular) to the board, and you are ready to solder the HDSP-2534 display;
  • insert the machined headers into the HDSP-2534 display first, then insert the HDSP-2534 display with the attached machined pins into the adapter PCB until all pins are accessible on the other side;
  • solder the machined pins, on the side facing the main board (the bottom row is just underneath the main PCB, the top row is above the main PCB). In the end, it should look like in the photo below.


Then insert the display with the key (the "cut" corner) in the left bottom of the adapter.

As of Oct. 8, 2015, an HCMS-29xx adapter is available (shared on oshpark), for use with the "serial"  intelligent displays (as opposed to the "parallel" HDSP-2534 coming in the kit).