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post #11 of 35 Old 07-04-2014
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Re: Arduino / Raspberry Pi based instrumentation?

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?
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post #12 of 35 Old 07-04-2014
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Re: Arduino / Raspberry Pi based instrumentation?

nightOwl, you might want to read up on some of those systems and see what gearheads have traditionally done in cars.

A true "sender" for an idiot light may actually be a simple SWITCH. You can't convert that into a resistance-based sender, which typically changes resistance from roughly 0-240 ohms. So you need to find out what is on the engine and confirm what resistance range it is, or what range your replacement will be, and calibrate with it.

Extending or t-ing oil lines is also problematic. More lines, more fittings, and especially t's, tend to give you more oil leaks followed by total loss of oil pressure, a messy problem. That's why electric senders are considered the way to go, with no t's.

yes, you can kludge almost anything but you've got two distinct projects to sort out. One being the "simple" analog-to-digital conversion and display. The other being how to wire up sensors on an engine.
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post #13 of 35 Old 07-06-2014 Thread Starter
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Re: Arduino / Raspberry Pi based instrumentation?

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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?
Here are my goals.

1 - true sensors that aren't simple idiot lights/buzzer
2 - sensor should send the data not to the helm, but utilizing arduino to the raspberry pi
3 - raspberry pi should (via kplex) route data to boats wifi network.


This would allow me to use my Win81 tablet to see engine sensors data along with other instrumented data (wind, depth, ais) on a tablet.

S/V Jendai
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post #14 of 35 Old 07-06-2014 Thread Starter
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Re: Arduino / Raspberry Pi based instrumentation?

So, update on this project. Hit a stumbling block in the most unexpected place. Oddly enough, AIS when plugged into the Pi repeats over wifi...but *NOT* when directly plugged into my macbook (com issue???). Even stranger, nmea instruments plug into the macbook and display just fine...but WONT when I plug them into the pi. FRUSTRATING!

This picture shows AIS coming via wifi, but NMEA0183 still had to be plugged into the laptop.


Back to the engine instruments.

Yes, I agree..."teeing" into oil pressure seems risky. However how else would preserver the idiot light sender (already there) and then add the proper analog sender for true pressure readings?

S/V Jendai
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Re: Arduino / Raspberry Pi based instrumentation?

Well - I think I figured out why the data isn't flowing for NMEA. Tore the whole aft cabin apart to get to the Raymarine NMEA interface box. After plugging the pi directly into the box (you should see the ghetto setup...Ryobi 18v battery, dc-dc converter, alligator clips, a zip tie), I was able to see NMEA data flowing to the Pi.



Apparently, the USB cable is too long for the Pi to power. I was afraid of this when I ordered my equipment because a marinized USB hub is $50....half the project cost! Was hoping to squeak by with a passive USB hub, but no dice.


So, another trip to Amazon and this project will be continued *NEXT* weekend. Now, back to my dayjob

*edit*
a pic of the ghetto temporary setup. Notice the amazon box housing the dc-dc converter and the 18v ryobi battery powerpack!


S/V Jendai
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Last edited by night0wl; 07-06-2014 at 10:06 PM.
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post #16 of 35 Old 07-07-2014
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Re: Arduino / Raspberry Pi based instrumentation?

There are a lot of DC to DC power supplies available for under $10. I'm using this one for my Netduino-based wind instrument:
Amazon.com: Retailstore 2PCS LM2596 Buck DC-DC Adjustable Step Down Power Supply Module Converter New: Computers & Accessories Amazon.com: Retailstore 2PCS LM2596 Buck DC-DC Adjustable Step Down Power Supply Module Converter New: Computers & Accessories



It works for me, but there are tons of other options to select from as well.

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post #17 of 35 Old 07-07-2014 Thread Starter
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Re: Arduino / Raspberry Pi based instrumentation?

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There are a lot of DC to DC power supplies available for under $10. I'm using this one for my Netduino-based wind instrument:
Amazon.com: Retailstore 2PCS LM2596 Buck DC-DC Adjustable Step Down Power Supply Module Converter New: Computers & Accessories

It works for me, but there are tons of other options to select from as well.
Yep, I considered this one, but chose
Amazon.com: DC-DC Converter Module Step up and down In 3.5-28V Out 1.25-26V Adjustable (LM2596S+LM2577S): Car Electronics Amazon.com: DC-DC Converter Module Step up and down In 3.5-28V Out 1.25-26V Adjustable (LM2596S+LM2577S): Car Electronics


. Simply put, I wanted the input voltage to always be 12v. Sometimes boat batteries can drop below that due to discharge, so I wanted the ability of the Pi to keep running. Those step downs wont work in that situation.

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post #18 of 35 Old 07-07-2014
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Re: Arduino / Raspberry Pi based instrumentation?

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.
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post #19 of 35 Old 07-08-2014
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Re: Arduino / Raspberry Pi based instrumentation?

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Simply put, I wanted the input voltage to always be 12v. Sometimes boat batteries can drop below that due to discharge, so I wanted the ability of the Pi to keep running. Those step downs wont work in that situation.
I thought that the Pi could run on 5V, but didn't look closely at it. My Netduino wants 7-10V ideally, so a step-down only power supply was more than adequate.

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Re: Arduino / Raspberry Pi based instrumentation?

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I thought that the Pi could run on 5V, but didn't look closely at it. My Netduino wants 7-10V ideally, so a step-down only power supply was more than adequate.
You know you're right. But I dont have the pi hardwired. It goes through a 12v -5v brick...or through a usb hub which takes in 12v. Just wanted the 12v to be steady.

S/V Jendai
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