Boat Projects Forum

Regal 2250 - Remote boat monitor

by mlines » 26 Nov 2015, 08:00

Ed,

Yes, I think it should fit on 10x15cm, although I also am making space for the GPS, RTC and Motion detection boards as well so that I can do my planned upgrades next year.

However the free version is limited to 10 x 8 cm and was constantly reporting everything did not fit. I would think that if I got aggressive with it I could have made much better use of the room but I want to put the components on first and then optimise rather than fight for every component.

What connectors would you recommend? I think I have a choice between putting headers on the PCB and the connectors on the case or connectors direct on the PCB. The disadvantge of the first is that I would have to make up wiring within the case and this is quite an effort. A couple of other designs I have seen use PCB mount RJ45 connections and then ethernet cables for the remote sensors, this makes the cable cheap and off the shelf?

I will have 3 x Sensor and 3 x Battery inputs. I have also thought of 3.5mm jacks for the sensors and small Molex for the batteries?

Martin
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by annageek » 26 Nov 2015, 10:19

A couple of other designs I have seen use PCB mount RJ45 connections and then ethernet cables for the remote sensors


... and twisted pair = good for noise immunity.

If it were me, I'd probably have a 9-way D-SUB per 'zone' of sensors. Still use ethernet cable (as it's cheap), but the D-SUBs will stand up to the environment MUCH better (RJ45s will develop impedance over time because of the combination of vibration, thermal cycling and moist, salty air). You could then have smaller 'sensor boxes' in each 'zone' which can be sealed up if required (IP68 D-SUBs are available if needed, too). and contain any local support/safety electronics. Like:

diagram.jpg
diagram.jpg (61.46 KiB) Viewed 736 times


If you really wanted to be clever, you could limit yourself to only using 3 of the ethernet cable's twisted pairs wires in each zone, and connect a resistor between the 4th - this way, you can put a top half of potential divider in the main unit, and the main unit would then know the type of sensor box connected to each port.

Perhaps this is over complicating thins, but it'd be just as easy to put together, neat, not too much more expensive, and crucially safer and more reliable.
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by _Ed_ » 26 Nov 2015, 10:39

Martin, sorry yes the freeware version is 100x80mm. You could still do all you wanted on that. Its good to design stuff as small as possible as well. GPS, RTC and Motion detection could all be on stand-off modules. RTC module like this http://www.ebay.co.uk/itm/DS1302-Real-T ... H5uIy_KWSw could stand off the board vertical, depends how creative you want to get ;)

Anna is correct with her choice of alternative plug. RJ45 (exposed) is just NOT for marine use!! I quite like these: http://www.ebay.co.uk/itm/SD16-16mm-7-P ... SwgQ9VjKFc I have had a few samples now and they are for the money really quite nice indeed. Another idea is to have IP rated cable glands, http://www.ebay.co.uk/itm/10-x-12mm-Com ... xyfyhRX~Oq which you pass the Ethernet cable through into your case, and then crimp terminals on and connect to the boards at each end. That would be a very cheap way and still use RJ45 connectors.
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by mlines » 26 Nov 2015, 11:15

Thanks, this input is great and I am taking it all on board, hope others on the forum can tolerate geek talk.

As for the marine environment, how "marine" does it need to be. The monitor I have in operation is inside the warm, dry boat on a trailer and it is designed to alert the moment the environment becomes not warm and dry. I am trying to make cable assembly as easy as possible as my past experience is that plonking components onto a pre-made PCB is simple. IP rated connectors and cases will push the costs up and cable construction difficulty (assembling glands etc.)
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by _Ed_ » 26 Nov 2015, 11:22

It needs to/should be 100% marine. Glands are easy on Ethernet cable and very cheap/quick too. You don't want to have to remove it surely when taking the boat out? If you are relying on the device to report of potential extreme conditions, it needs to be able to live in them for extended periods of time as well :)

I know from experience on my Fletcher, that everything has to be pretty much bomb proof for it to last longer than a season lol...
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by mlines » 26 Nov 2015, 11:31

annageek wrote:
If you really wanted to be clever, you could limit yourself to only using 3 of the ethernet cable's twisted pairs wires in each zone, and connect a resistor between the 4th - this way, you can put a top half of potential divider in the main unit, and the main unit would then know the type of sensor box connected to each port.

Perhaps this is over complicating thins, but it'd be just as easy to put together, neat, not too much more expensive, and crucially safer and more reliable.


Thats an interesting idea because it then could cope with either 12v or 24v systems, however my brain hurts :)
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by mlines » 26 Nov 2015, 11:33

_Ed_ wrote:You don't want to have to remove it surely when taking the boat out? .


At present thats exactly the concept, it jsut croc clips onto the battery and sits on the floor of the boat, the moment the boat is used it is unclipped and removed.
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by _Ed_ » 26 Nov 2015, 11:46

mlines wrote:
annageek wrote:
If you really wanted to be clever, you could limit yourself to only using 3 of the ethernet cable's twisted pairs wires in each zone, and connect a resistor between the 4th - this way, you can put a top half of potential divider in the main unit, and the main unit would then know the type of sensor box connected to each port.

Perhaps this is over complicating thins, but it'd be just as easy to put together, neat, not too much more expensive, and crucially safer and more reliable.


Thats an interesting idea because it then could cope with either 12v or 24v systems, however my brain hurts :)


If you run the main box and power all the sensors from that on a DC-DC psu then it will run on anything upto 30+v and be fine, and efficient.
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by _Ed_ » 26 Nov 2015, 11:47

Which is fine, but once you get sensors everywhere then it becomes a chore. I'd want to leave it in running on boat power so when away on trips and leaving it at other marinas I'd know its still there and safe :)

I'd also have bilge pump float switch input as well...
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by mlines » 26 Nov 2015, 11:57

_Ed_ wrote:
I'd also have bilge pump float switch input as well...


Excellent idea. I think this is going towards simply breaking out all the digital and analogue inputs and producing little separate "sensor" PCBs that plug in.
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