Do it yourself marine electronics

Do it yourself marine electronics

Science fair crystal radio kit
Look Mom, no batteries!
If you want a thing done well, do it yourself. – Napoleon Bonaparte

If you remember the Science Fair crystal radio kit available at Radio Shack in the 1970s, you know how long its been since I attempted to build anything electronic. Recently I was reading about an autopilot project that used this inexpensive micro-controller (computer) called the Arduino. Curious, I started researching the Arduino project and soon realized that lots of “maker” hobbyists were building all kinds of kool stuff with it. Electronics are now more accessible to everyone, kids are making awesome projects. I particularly like this autonomous boat drone project.

What could I build for my boat?

I should say that personally I’d leave it to the pros to build my autopilot. I’m pretty certain I couldn’t do a better job and my passengers are thankful for this opinion! Marine electronics are pricey, but when you start analyzing everything that goes into them such as: waterproof sunlight viewable displays, robust networking, reliability, extensive testing, and the relatively small market opportunity, you can understand why they are priced the way they are. However, it doesn’t mean that we can’t augment our boats with useful but less critical do it yourself projects.

The Arduino is great because you connect inputs and outputs to it and use text based code (called a “sketch”) to program its behaviour. With the hundreds of examples of projects online, it is fairly easy to try your hand at building something. There are tons of different sensors you can attach including thermometers, barometers, accelerometers, you name it. The Arduino and various sensors, switches etc., can be had on the Internet for $10 or less!


There are also things called “shields” which you can buy to add other functionality. A shield is typically another board that plugs into the Arduino such as this ethernet shield so you can network your project. Shields add functionality while also giving you full access to all the pins on the Arduino via a pass thru system.

I’ve had this Raymarine M81105 rudder reference transducer in my closet for quite awhile waiting for the day I can afford an autopilot. I picked it up on an eBay auction for about US$60. Even without an autopilot it is a useful thing to have installed on your boat. Often in tricky and tight docking situations you don’t have time to “find by feel” where the rudder is centered. An indicator showing you the position of the rudder is handy to have and a good starting point for a DIY project.

You can imagine my skepticism about my ability to program micro-electronics. It turned out it was easier than I thought. When I realized that the rudder reference transducer is basically a large potentiometer (creating variable resistance values in ohms), it was easy to find a project that started me in the right direction. I fooled around a bit with the code and before long my prototype was done. I used 5 coloured LEDs to create a nine position rudder reference indicator.

Rudder angle LEDs retro
It’s retro but it works!


The hardest part of the project was the actual installation of the rudder reference unit. I don’t have a nice case for the Arduino yet, but will let you know when I find one I like. I need to find a case that will also nicely hold the ethernet shield which I’ll use in future projects.

A dedicated display gauge that interfaces with a rudder reference unit costs hundreds of dollars. If you want crazy pricing see this one for US$1270This project costs less than US$40 not including the transducer. If you can’t afford an autopilot or a dedicated gauge, you now have another option. An Arduino also provides an upgrade path for future projects like remote switching, temperature monitoring, boat level gauge, alternator regulator, or whatever you can dream up.

How to guide

I have written up the complete “how to guide” for my rudder reference indicator project. If you keep an eye on this blog we’ll be adding to the capabilities of my Arduino Uno with digital DC switching and remote viewing and control. We’ll explore Apps to control it all. Eventually if all goes well with SignalK, I want to have my Arduino send data through my iKommunicate gateway to my chartplotter (via NMEA 2000) for display on my command bridge. Stay tuned.

I hope I’ve inspired you to try your hand at building your own marine electronics!

– Safe Boating –


  1. You can find some neat Arduino boat projects on my blog. From an aquabot with an intelliducer, GPS and logging for depth mapping a lake with flooded trees. A GPS/NMEA multiplexer?logger and a simple weather station (Temp, Humidity, dew point, heat index, and barometer) that I'll probably convert to Bluetooth. The other thing that makes it all possible is a 3D printer