I've looked for solutions and found the ScanGauge II trip computer quite interesting. But considering it's priced at €150 and is basically an OBDii interface with a microcontroller and an LCD display I decided I can probably build something better and cheaper myself.
A while ago I found the excellent swedish "electronics hacker store" electrokit and have been thinking about a suitable project to revive some of the things I learned while studying at ISY. So I ordered some AVR microcontrollers, LCD displays, voltage regulators and fired up the soldering station for the first time in a while.
Here is a picture of the current project status:
|Work in progress trip computer|
On top is the AVR microcontroller. It's a surface mounted package which comes presoldered on a breakout board under the Arduino brand name. It also comes with a pre-installed boot loader for rapid prototyping, which is nice.
The flat cables are dual HD44780-compatible LCD display outputs wired up to the AVR. Embedded in the hot-melt glue are also two NPN transistors and resistors for driving the LCD backlights with PWM.
Not pictured is the TTL conversion circuitry for the car diagnostics port. I will probably finish that part tonight.