Otemba

Otemba : Tomboy in Japanese.

Tokyo Hackerspace's very own Arduino clone.

Why another Arduino clone ?

• Really cheap (< JPY1000 all parts and PCB included, we could sell kits for profit, PCBs only for less profit)

• Great for the introduction to arduino/soldering class.

• We would always have an arduino handy at the hackerspace.

• It would fit nicely in the vending machine! We could sell it on the website. There could be a discount for members, or you could get just the PCB when you join so that you readily have a first project to do at the space (get the parts at akizuki and put it together).

• It has the hackerspace logo and stuff!

• It would make a great final end of a crazy THS guided Akihabara tour. Could be a geek tourist kit.

Board Assembly

Checkout the board (5V version) assembly instructions.

Bootloader

For some help burning the bootloader, refer to the Arduino website.

• 5V/16MHz : use the standard Arduino UNO bootloader,

• 3.3V/8MHz : use the 'Arduino Pro or Pro Mini (3.3V, 8MHz) w/ ATmega328',

• 3.3V/8MHz, no crystal : see the minimal circuit description at the end of this page.

Upload sketches

To lower cost, the Otemba doesn't have an FTDI serial-to-USB chip on-board. So to upload sketches to the board, an FTDI serial-to-USB dongle is necessary. These can be bought from Sparkfun or adafruit. For example here is a 5V version and a 3.3V version, depending on what board setup you use (normally it is 5V). Here is a cheap ass way of making such a cable.

Bill Of Materials

• 1x 10K resistor (R1) akizuki
• 1x 1K resistor (R2) akizuki
• 3x 0.1uF capacitors (C1, C2, C3) 2.54mm pitch akizuki
• 2x 22pF capacitors (C8, C9) akizuki
• 1x atmega328p akizuki
• 1x Tactile Switch 2.54mm pitch akizuki
• 1x 16MHz crystal akizuki
• 1x 3mm LED akizuki
• 1x6 and 1x20 pin headers (90 degrees) akizuki
• 2x3 pin header (straight) akizuki

Regulator (optional)

• 1x TA48M05F 5V, 500mA regulator
• 1x 47uF electrolytic capacitor (C4)
• 1x 0.1uF capacitor (C5)
• 1x 2.1mm barrel jack akizuki

Regulator and capacitors sold together at akizuki.

Battery Booster (optional)

• 1x HT7705A 5V, 200mA booster akizuki
• 1x 47uF electrolytic capacitor (C6) akizuki
• 1x 22uF electrolytic capacitor (C7) akizuki
• 1x 47uH inductor (L1) akizuki
• 1x Shottky diode, 200 mA akizuki
• 1x Optional connector JST XH-2 (2 pins)

3.3V/8MHz version

It is possible to make a 3.3V/8MHz version of the Otemba by using an 8MHz crystal (instead of 16), the TA48M033F (instead of TA48M05F) and the HT7733A (instead of HT7705A).

In that case, it is also possible to completely omit the crystal, C8 and C9 and run the board on the internal oscillator.

Get Otemba PCB fabricated

The Gerber files necessary to produce Otemba boards can be downloaded here : tar zip.

PCB can be fabbed anywhere you like, but if you don't know how to start, checkout the Seeed Studio Fusion PCB Service. It is cheap and quick. The lowest quantity is 10 boards for 10$. On their website, simply upload the zip file containing the Otemba Gerber file. The board size is 5x5 cm. All the default options should work just fine.

License

2012 (c) TokyoHackerSpace, License CC-BY-SA 3.0.