I'm way behind the curve here but fancied a go at ultra-low cost boat instruments. Robinetta has a 1970s depth sounder and a small chart plotter and that's about it. Alison would like wind speed and direction and it would be nice to know boat speed. Remoting the depth information to the cockpit would be nice.
There are freeware and open source chart plotter applications now. It should be possible to do most things at very low cost.
I'm going to start with a magnetic compass because that seems easiest. We don't need it but it will talk to the chart plotter and/or the tiller pilot using serial NMEA.
BOM
Arduino Nano v3 £8.56
HMC5883L triple axis magnetometer £1.88
SN75176AD EIA422 transceiver £0.26
Prototyping Box £1.77
I've made a gimbal mount out of scrap plywood and I'll mount the magnetometer on that and the arduino and bus transceiver in the prototyping box. They will be wired together with flexible wire left over from a Round-the-pole model aircraft toy I made.
I'll try both USB power and raw boat 12V.
I haven't worked out if the UART is available when the USB is not plugged in but I should be able to use s/w serial port on digital I/O pins.
