Sunday, July 5, 2015

Introducing wsduino

This project is actually a revisit of my old Wiseduino, with the same goal: an Arduino-compatible with on-board Real Time Clock, and some extras (in this case, an XBee-like device, e.g. BTBee, GPSBee, WiFly). I renamed it "wsduino", although the pronunciation should remain the same :)

I redesigned wsduino mainly for the Axiris IV3 clock, whose enclosure allows for only 2 boards (Arduino + IV3 shield), with openings for power socket, USB, and no accessible buttons. Essentially, wsduino saves you an extra shield, which would have hosted the RTC (+backup battery) and the XBee.

 US$27 - free shipping to North America

wsduino is now available as a kit, as shown in the photo below.

The wsduino kit includes:
  • PCB
  • ATmega328 processor with bootloader
  • 28-pin socket
  • 16MHz crystal
  • 2 x 22pF capacitor
  • power jack
  • 7805 voltage regulator
  • 1N4001 diode
  • USB miniB socket
  • DS3231 RTC (SMD)
  • A1117 3V3 regulator (SMD)
  • CR1220 battery + holder
  • 4 x 10k resistor
  • 4k7 resistor
  • 3 x 100nF capacitor
  • 47uF/25V capacitor
  • 47uF/16V capacitor
  • 470uF/10V capacitor
  • 2 x 10-pin 2mm female header for XBee
  • 40-pin 0.1" female header
  • 3-pin header + jumper (selection of power source)

An FTDI breakout is required to upload sketches.

Although the assembly is quite trivial, I enumerate below the steps, for the detail-oriented :)
  1. solder the DS3231 SMD chip on the bottom of the PCB, making sure the chip orientation is correct;
  2. solder the A1117 chip, also on the bottom of the PCB;
  3. solder the resistors R1-R4 (their values are shown in silkscreen);
  4. solder the IC socket, with the correct orientation of the notch; then insert the ATmega328 chip (after you bent the two sides of pins on a flat surface, one side at a time, to become parallel);
  5. solder the crystal (orientation does not matter)
  6. solder the USB miniB socket;
  7. solder the 7805 voltage regulator to match its shape in silkscreen;
  8. solder the ceramic capacitors (orientation does not matter);
  9. solder the 3 electrolytic capacitors, paying attention to their orientation;
  10. solder the diode, also paying attention to its orientation;
  11. solder the power jack;
  12. solder the 2 XBee headers;
  13. cut, then solder, the extension headers;
  14. solder the battery holder, then insert the battery.
Schematic and board layout are shown below.

Here are some photos of the assembled board.

A  minimal wsduino is shown below, with the ATmega328 running on the internal oscillator at 8MHz, powered directly through the USB miniB socket.

The RTC (DS3231) and 3V3 voltage regulator are soldered on the bottom.

Perfect Arduino-compatible to quickly build a clock. Just add a display shield :)

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