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Old 12-19-2015, 02:31 PM   #23
R_p_ryan
Senior Member
 
City: San Francisco
Vessel Name: Shellbourne
Vessel Model: 1978 Mainship 34 Perkins T6.354
Join Date: Dec 2014
Posts: 171
These are great ideas.
The ScanGuage display is similar to what I was thinking. A compact unit with a button to display the next sensor's output. Thanks for the link to it, the user-interface provides some guidance.

The PLC route is definitely something to consider. I've used a PLC before but found it more difficult to program than an Arduino. The device could be SignalK-compliant, and provide a JSON endpoint to return engine statistics. And putting it on wifi is also a great idea since it could send me a text message when my bilge switch turns on. I'm thinking an Agile approach makes sense, and we can focus on small iterations.

The vastness and cheapness of the Arduino platform is appealing, as is the open-source nature of it. With all the shields available there is an unlimited degree of flexibility. I think Waspmote is pretty interesting too.

Regarding reinventing the wheel, we should disclaim this project is for the maker / do-it-yourself type and the system is not to be depended on when safety is at stake. If you're looking for a proven, purpose-built, marine-grade, bolt-on device then this isn't it. This is for the person who enjoys creating things, is on a budget, and wants more information from his/her engine.

Stubones99:
Thanks for the information. I agree with the DC-DC converter. You bring up a good point with the opto-isolation. I've been assuming this is for a marine diesel, so there wouldn't be the EMF of a gasoline ignition. Can you explain the need for opto-isolation? I don't know how we would be able to provide opto-isolation of the arduino from the sensors. Each sensor will have a pull-down resistor that should help dissipate stray energy. Currently I have the Arduino connected to my EGT using a simple K-type thermocouple with a small converter board and haven't had any issues. I'm playing with the magnets and the sensor for the tach - I could imagine getting stray energy from the alternator. Can you please explain more about the opto-isolation?

The first iteration:
What do people think about oil temp, tachometer, and EGT as the first three sensors? I'm thinking the Arduino would be mounted in a case on the bulkhead in the engine room, with a compact display/button similar to what_barnacles suggested in the ScanGuage design. The display/button would be connected to the Arduino using a CAT-5 cable. The display could be something like a 16X2 in a small enclosure.

Thanks,
Robert
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