Tuesday, January 26, 2010

What a difference...

... can a header/connector make.
Until today I used to plug the 8x8 LED matrices into these cheap and ubiquitous 40-pin female headers:
The round and thin pins of the LED matrices won't fit snugly the wide gaps of the above female headers. These headers are designed to work best, I strongly suspect, with the thick rectangular pins of the, also ubiquitous and cheap, 40-pin male header:

My LED matrices did not make firm contact when plugged into the above pictured female headers. Even scarier, every little touch seemed to affect the contacts, regardless of my efforts to find an easy solution (bend outwards the matrix pins a bit, thicken them with solder, insert them as deep as I could etc).

The final and permanent solution was to replace those headers altogether, with these round machined female pins:

They are a bit more expensive, but make a huge difference in terms of firmness of the contact.
They are also shorter, bringing the LED matrix closer to the board. That requires some attention when sockets are to be used: they should be either inside or outside the matrix package itself.
(Unfortunately I am talking from experience, since I had to remove a socket which was spread under two matrices.)

A different topic, but under the same umbrella of lessons learned: buying and using USB adapter power sources.
To shorten the story, this is the conclusion: when you buy such an USB adapter, never assume the output is 5V and just plug it into your expensive device!
Out of about 10 I bought on ebay, shipped from their manufacturers in China, 2 of them output 9V, way above the expected 5V. Although not statistically accurate (is there such a thing?), this is a 20% failure rate. Before plugging it on, always measure the output voltage to make sure it is what you expect.

Saturday, January 16, 2010

Complete "Wise Clock 2" kit for sale

Updated May 5, 2011
The "Complete Wise Clock 2 kit" is DISCONTINUED due to the lack of displays from Sure Electronics. If you have your own 2416 display, you can still buy the Duino644 board to make the Wise Clock 2.

Updated Jan 27, 2011
"Wise Clock 2 complete kit" is back in stock. The Duino644 board is re-designed, with the following changes for revision 2.1:
  • the real time clock can be either DS1307 (and crystal) or DS3231;
  • the on-board EEPROM (which was not used by the software) was eliminated;
  • the voltage dividers with resistors were replaced with 74125 gates;
The price remains the same (US$88 with free shipping, see below) for the DS1307 version. The version with DS3231 is $5 more.
Read more about Duino644 revision 2.1 here.

Updated Jan 1/2011
"Wise Clock 2 complete kit" is currently out of stock. It will be available again around the end of January 2011.

Updated June 17/2010
Starting today, "Wise Clock 2 complete kit" has the ATmega644P microcontroller loaded with the latest version of the "Wise Clock 2" software (this is on top of the bootloader, of course). This means that after assembling it, there is no need for ATmega644P chip to be programmed anymore; this eliminates the need for FTDI cable, Arduino IDE, code download, compilation, upload, and greatly simplifies the construction of the clock. (Obviously, the software can be changed/upgraded any time through the FTDI connector).

I recently received a batch of laser-cut acrylic covers designed as enclosures for the Wise Clock 2.
I decided to offer for sale a few complete Wise Clock 2 kits, which include:
  1. microcontroller board: Duino644 kit;
  2. display: red 16x24 LED matrix, from Sure Electronics;
  3. enclosure: 2 laser-cut acrylic plates, plus the auxiliary hardware (spacers, nuts, screws).
You can buy them for US$84, shipped free to any destination in North America.

 (US$88, free shipping to North America; I only ship to North America)

The assembled Wise Clock 2 should look pretty close to this one:

Note: Wise4Sure is the obsolete name for the Duino644 board. Duino644 can be used independently of the display from Sure Electronics, for example as the base for uzebox game console.

The photo below shows the content of the kit.

Assembling instructions are provided in this step-by-step "instructable".

In summary, Wise Clock 2 can currently (with the latest software release) do the following:
  • display current time;
  • read a user-editable file from SD card and display its content as quotations (hence the name "Wise Clock");
  • display current date;
  • set/trigger/sound/enable/disable alarm;
  • controllable from a Sony TV remote control;
  • user-selectable brightness for the high visibility display;
  • user-selectable speed for the scrolling text.