Lighting Digital Control System

I have a question about a Digital Lighting Control System on my boat that is no longer working. I know this is not exactly a home automation issue, but @Superhouse seems to deal with similar issues in an understandable way.

my boat was built in 2002 with a digital switching system for lights and heater fan. It consists of five push-button switch pods with a total of 16 switches. Each pod is constructed on a PCB. The switch pods are daisy chained to each other and to the control unit with 4 wire cable and with DT Duetsch Connectors at each switch pod and at the control unit. When a switch is activated, a back-lit light illuminates at the switch. The control unit has 16 relays connected to the loads via fuses (7 at 5A, 7 at 10A, 1 at 15A and 1 spare). The system was built by Carling Technologies for Tomco Marine and installed in about 50 American Tugs (the boat I have). The control unit on my boat has now failed, and Carling no longer supports the product. The control unit is potted, so I assume it can not be repaired. I would like to find a way to continue using the wiring harness and, hopefully, the switch pads, since they are installed throughout the boat and buried in the finishes. I need to find a replacement for the control unit. I am hoping an Arduino based system would work, but my understanding is pure beginner.

The 4 wire harness has red, black, green and white wires. The red and black test as 5V supply and ground from the control unit. I haven’t been able to find out how the switches/pods communicate with the control over the shared harness.

Any explanation of how the control side works would be appreciated, as would an approach to solving my problem.

Regards, franksilkwood

Might simply be CAN bus…

I think it probably is CAN bus. The nodes consist of six switch-pods (with a total of sixteen switches) and a control unit. Is there a way to replace the control unit while retaining the switches/pods and wiring harness? Would an Arduino micro controller work?

It’ll take some research into the CAN messages being sent by the switches, but should be doable.
I haven’t done anything with it yet to learn how it works, but I picked up a CAN receiver module that supposedly works with Arduino.

How many switches are in each switch pod and is there any electronics in the pod? Are any of the wires shielded? Can bus might be more complicated than you need depending on the number of switches at each pod. It might be easier to use an I2c serial connection to the “Brain box”. If you had a cheap signal analyzer or oscilloscope you would have a better idea of the signaling. You can buy a pocket oscilloscope from for under $50. They even have a cheap multimeter with a digital O-scope for about $50-60. You said that the voltage at the pods is 5v so it would be easy to devine the separate switch signals using a cheap ±5v scope. Once you know how the switches talk to the Brain, coming up with a communication protocal and talking to an arduino “brain” is just a mater of a good google search, some cheap components and copying or maybe modifying a sketch from one of the bazillion sources on the arduino sites. Check out this link to Bangood for some O-scope info
Good luck and let us know what you find. I cut my electronic teeth as a kid doing wiring on boats. Dad had a charter boat and I was the chief mechanic and all around maintenance guy. No arduinos then, the radios still had tubes.

Are you still trying to solve this problem, or have you sorted it out?

As others said, CAN bus seems likely since Carling Technologies openly state that they use it in their current products. For example:

There are two switches in three of the pods, four in one and six in the final pod (total of five pods). The wiring harness cable is Shielded DR AWM 2464 with 4 conductors and Deustch DT connectors at each pod and at the control unit. Each switch pod has an printed circuit board with micro switches, a microcontroller, a relay and many capacitors, etc.

Pretty sure I’ve confirmed the system works with a CAN Bus protocol. Originally I thought the Control Unit was bad because none of the switches were working. But, I discovered that one of the switch pod was defective and allowing the full five volts out on the CAN Bus wiring and shutting the system down. A bad capacitor was replaced and the now everything is working. However eventually I am going to have to replace the system, so how to do so is still a question. I will want to stay with something that does not require replacing the wiring harness cable.

Thanks for your thoughts. I was planning to get a CAN Bus analyzer to see if I can read the messages on the network.