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Arduino / Raspberry Pi based instrumentation?

15905 Views 34 Replies 14 Participants Last post by  BryceGTX
Hi all,

So I recently ordered a Raspberry Pi and more associated small equipment to make myself a NMEA wireless bridge/repeater. The plan is to (based on a recent Panbo article) utilize a Win8.1 cheapo tablet to run OpenCPN. I've already run the instrumentation and had it all working on my laptop at the helm, and even had OpenCPN acting as a TCP this is no challenge.

*HOWEVER*, this project got me thinking. My Yanmar 3ym30 has only the idiot lights for water temperature, voltage, and oil pressure. At various stages, I've thought about upgrading the Yanmar Panel ($1000+ all in), buying the Maretron N2k instrument andharness ($700 all in), and the cheapest option, splicing in to the existing wiring and putting in analogy instrument gauges.

Then, I thought, hey, I have the raspberry pi. Why not use an arduino board to tap this data this way!?

The trouble is, I'm not very well versed with arduino and instrumentation. However, if I'm willing and able to fund the hardware purchase(s), is there anyone that can guide me through the project? The best thread I've got is this as a reference: Boat Digital Guage Project - Arduino Forum

I figure I'd start with a simple here goes:

Q1 - can someone tap into existing idiot light gauges (at the sender or at the panel) in order to splice the data? How does one interpret the values being returned by the sender gauges (assuming they return various voltages or resistances back to the idiot lights helmide).
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How/where is the NMEA 2K decoding being done? OpenCPN able to decode 2K? 2K first converted to 0183 by? etc. Thanks.
Still not clear on what you are trying to do. An analog sensor to NMEA 0183 converter? Or an analog sensor to NMEA 2000 converter? If the later, how do you intend to obtain the NMEA 2000 protocol spec information?
I've built some simple things out of Arduino. Looks like from a brief search the Raspberry Pi system doesn't have an on board A/D converter, but people have built them and there maybe some kits.

If you have analog sensors for things like oil pressure, I don't see why you couldn't design a high impedance interface that would just go in parallel across the sensor with whatever gauge you got to measure a voltage level without impacting the gauge. Then you could infer a resistance level and translate in code to an oil pressure for example.

I've never really dug into the NEMA stuff, so no help there.

Warning, every time I start messing with some hack like this, it's more work than originally planned:) Best of luck.
Consider using the Beaglebone Black. Its got an on-board ADC. Generally better equipped for interfacing to real world versus the Pi.

Still not sure what you are trying to accomplish here. Conversion of several analog signals to an NMEA 0183 data stream? Or conversion of several analog signals to an NMEA 2000 data stream?
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