Need help with Raspberry Pi, Open CPN and using old instruments

[jjccp]

I’m new to using the Raspberry Pi, Open Plotter and Open CPN, but I’ve done a ton of reading about the systems. I don’t know a thing about Linux programming, but I’ve managed to get started only using the GUI. I’m also new to wiring instruments and understanding NMEA standards.

So far I’ve got the Raspberry Pi running with Open Plotter and Open CPN installed at home while learning everything. I’ve got a GPS antenna and charts installed and working. Next I want to get instruments working. I have a (new to me) Raymarine ST 60+ wind transducer and hope to have the display soon.

I inherited some old depth and speed transducers already installed in my boat. Depth is working with a Uniden QT 206 display and I’m not sure which depth transducer is currently connected there are 2. One is an Airmar and one is unknown at this time – see pics. Speed is an old Moor knotmeter transducer and display – not working.

Here are my questions:

1) Once I get the Raymarine wind instruments working, what is the actual hardware interface that gets the signal inputted to the Raspberry Pi?

2) Should I take the time to even mess with the old depth and speed units or should I buy something like the Airmar DSTn 800 that offers depth, speed, and temperature all in one unit? Of course I’d like to save the money and not have to buy a new transducer and I’m also on a mission to repurpose old stuff. I don’t mind taking the time to troubleshoot the old units, but does it even make sense to try to use the old stuff?

3) If I buy a new Airmar speed/depth/temp transducer, will it fit in one of my existing thru hull openings?

4) Once again, what is the actual wiring or hardware interface between the depth/speed transducer(s) and the Raspberry Pi?

I hope that all makes sense and Thanks in advance for your help.

[Reefmagnet]

for 1) and 2) You will need an NMEA 2000 gateway with a USB interface for a new DST800. If your existing transducers are NMEA 0183 then you'll need a USB to RS422 converter for each NMEA 0183 device you want to connect to the Pi. If it were me (and I do have Rpi/OpenPlotter setup), I'd stick with the existing transducers for testing because the RS422-USB converters can be picked up for a couple of bucks each on Ebay.

[jjccp]

Originally Posted by Reefmagnet

for 1) and 2) You will need an NMEA 2000 gateway with a USB interface for a new DST800. If your existing transducers are NMEA 0183 then you'll need a USB to RS422 converter for each NMEA 0183 device you want to connect to the Pi. If it were me (and I do have Rpi/OpenPlotter setup), I'd stick with the existing transducers for testing because the RS422-USB converters can be picked up for a couple of bucks each on Ebay.

Thanks for the info Reefmagnet. How can I know if my existing transducers are MNEA 0183? The depth and the speed may be really old and original to the boat, which might be from 1978 when the boat was new.

For the Raymarine wind instrument, is there a wiring diagram available to show how to wire it to the USB to RS422 conveter you mentioned?

[Reefmagnet]

Originally Posted by jjccp

Thanks for the info Reefmagnet. How can I know if my existing transducers are MNEA 0183? The depth and the speed may be really old and original to the boat, which might be from 1978 when the boat was new.

For the Raymarine wind instrument, is there a wiring diagram available to show how to wire it to the USB to RS422 conveter you mentioned?

You'd have to track the specs down for them, though if they're that old they may use proprietary connections to their own "black box". As long as you have something with NMEA 0183 you can test your setup first. Hooking up to the converter can be a bit of trial and error but you can't really destroy anything in the process.