After a bit of work on-line selecting the components we needed a couple of days in Eagle, to draw up the basic design (which like the code, I'm not releasing btw). I also had a design for the case, so we could start making things. The approach for assembly is to keep things flexible whilst we iron out the design issues - and to show the assembly methods to my children. At a future point, I'll produce the proper PCB's and miniaturise the platform a bit.
There are four main components to the system.
Going clockwise from the bottom left, they are :
- The Arduino Mega 2560 microcontroller
- The Adafruit motor controller board
- The Logic Shifter board (see below)
- The Raspberry Pi Model A
The Logic Shifter board is constructed from a Ciseco Humble Pi prototyping board which contains 6 main parts, from the bottom left, they are:
- The 8 channel 5V to 3.3V TXB0108 bi-directional level shifter from Adafruit
- The 3.5mm Serial console jack - for talking to the Raspberry Pi
- The 4 channel I2C safe BD138 logic level converter from Adafruit
- The I2C based Real-time-Clock module,which has the DS1307 RTC chip (top), a 3V battery for backup purposes and a Atmel AT24C32 4K of FLASH memory (bottom), which will be used for the event log. These modules are all over ebay
- The connector that goes to the main board and connect to the Arduino (GPIO and SPI)
- A Microchip 24FC1025 128Kb I2C FLASH memory chip
The board is just wired with some 30SWG tefzel wire I had lying around.