Wise time with Arduino

Saturday, September 11, 2010

New in the Shoppe: Wise Clock 2 - assembled, tested and ready for use

Updated May 5, 2011 - This product is now DISCONTINUED.

The latest issue (Sep 2010) of Elektor magazine has a catchy title on its cover: "Give your projects simple grace with the Elektor project case". Browsing the magazine curiously, I found out that the mentioned project case is actually the way I enclose my own projects, made out of two laser-cut plates of transparent acrylic. I am glad I am not far off from "perfection" :)

Since it cannot be said better, here is the quote from the Elektor article:

A brief tour of the World Wide Web clearly shows one of the problems facing many electronic enthusiasts: the enclosure. All too often it’s a plastic box in a dismal shade of grey, cluttered with an awkward arrangement of connectors, controls and indicators. You spent hours designing a stunning PCB layout, assembled the board neatly, and it ends up in a humdrum plastic box. Isn’t there a better way?

Starting today, for people who don't own (and are not interested in owning) a soldering iron, I am making available the assembled and tested version of the Wise Clock 2. It comes with the SD card, formatted and with the right files on it, the USB power adapter (5V DC output) and a 4-foot miniB USB cable (used to power the clock from either a computer or the USB adapter). In the assembled Wise Clock 2, the transparent acrylic plates are thicker, at 4mm (1/6"). The ATmega644 microcontroller comes programmed with the latest software (since new feature are added periodically). The display can be chosen between red and green.

Wise Clock 2 is shown in the photo at right and also in this video.

The clock is available for shipping to North America only, for the price of US$125, with free shipping.

Thursday, September 2, 2010

Cases for DWex

I've been looking around trying to find a solution for encasing the DWex watch.
A few ideas popped up:

use a case from an old pocket watch or stop watch;
build a machined-aluminum (CNCed) case from scratch (this would be an expensive venture), similar to that of the Nixie watch;
stich a tennis-cuff-like "soft case", with a transparent film material on top;
print a plastic case with a 3D printer (e.g. reprap);
screw together a few layers of laser-cut acrylic.

The last two solutions seem to be suitable for "mass production". Some plans (for Makerbot watch) are already available, but they may need to be adjusted to fit the DWex.

Here are some links I found after googling around:

Programming DWex

All DWex boards are shipped with the latest software (available here) loaded and tested. The on-board ATmega328 controller has the bootloader already burned in.

I don't expect users ("experimenters" in the case of DWex :) not to modify and improve the code. In fact, I have a long list of TODOs myself. To help speed up the process, here are some tips and heads-up.

1. To upload the sketches, use the 3V3 FTDI breakout board or the 3V3 FTDI cable (remember that the board is designed to work at 3V; it is 5V tolerant though).

2. Use a 6-pin male header between the FTDI cable/breakout and the DWex board, inserted as shown below.

3. Make sure that the "green" wire of the FTDI cable (also marked on the FTDI breakout) goes to the pin marked "Green" on the DWex board.

4. The CR2032 battery must be inserted in the holder when uploading the sketch. The DWex board is not powered from the FTDI cable/breakout (pin 4 of the FTDI header is not connected).

5. In Arduino IDE, select the board as "Lilypad with ATmega328", as shown in the screenshot below.

6. The available pins (not taken by LED matrix and button) are:

D11, D12, D13 (MOSI, MISO, SCK respectively) accessible through the ICSP connector;
D0, D1 (Rx, Tx respectively) accessible through the FTDI connector;
D2, accessible and marked on the board as JP2;
D10, not connected to any pad.

7. The second (un-soldered) holder would connect another CR2032 in parallel. Although at the beginning it seemed to boost the power supply, I realized after some research that it may not be a good idea after all. I am still debating on this and I am open to suggestions.

8. With the current code, to set the time, hold the button pressed for 3-4 seconds, until the LEDs light up in circle, one after the other. When the correct time is reached, release the button. The time will then be saved in the RTC. Obviously, this method does not confer the highest accuracy.

9. The state diagram for the current implementation is shown below.

DWex - an alternative to Makerbot watch

I always wanted to buy a Makerbot watch, but never had the chance. That's because they were (and still are, at the time of writing) always "out of stock" in the Makerbot store. Then I decided to make my own and better version, called DWex, an acronym for Duino Watch for experimenters (introduced here a while back). I actually borrowed some of the ideas from Makerbot watch, including the round shape :) and the LED arrangement, as two circles of 12 LEDs.

Here is a brief comparison between the two:

DWex is based on ATmega328 running at 8MHz (as opposed to 16MHz); that should make it take less juice out of the 3V coin battery;
DWex has only one button (as opposed to 3); and even that could be eliminated eventually (replaced with a tilt switch, for example);
DWex has 4 fewer LEDs; the way to show the time (software) does not require the extra 4 LEDs of Makerbot watch;
DWex spends most of its time in sleep mode (I don't know how Makerbot watch works though, to be honest, but I think time is kept by the ATmega chip itself; therefore, no sleep for it); it only wakes up when the button is pressed, to show the time;
DWex is thinner, and that may be due to the much bigger crystal used by Makerbot;
DWex does not have a buzzer;
Like Makerbot watch, DWex has both the ICSP and FTDI connectors on board, making it an "Arduino environment on your wrist" as well.
They both cost the same, US$30 (plus $3 regular shipping to North America). DWex is in stock though. It is real and working.

Some of the features of DWex are:

time is shown by lighting/flickering only two LEDs, for hours and minutes;
time can be set by the user through the button, without connecting the board to the PC;
consumption is 12mA when the time is shown, 120uA when asleep; the CR2032 coin battery should last at least a few months;
can be re-programmed to make use of the alarms of on-board DS1337 RTC (this functionality is not implemented, but the hardware capabilities are in place).

Nixie clock

I could not resist adding yet another clock to my collection. This one is Nixie, although not Arduino-based. I bought the kit on ebay and assembled it in a couple of hours. It's got a PIC microcontroller and a DS3231 "extremely accurate RTC". In the process I learned that Nixie tubes need around 170V to work, voltage generated by a DC-to-DC converter built with a 555.

Although the schematic is provided, the code is not.

Here are a couple of photos.