autohelm modification - installing a wired remote control
autohelm wired remote;
installing the circuit extensions.
by Adrian Biffen
I had to take the autohelm apart
in order to make the modifications for the wired remote. The top half of the unit unscrewed easily and separated from the continuous gasket that forms a weather tight seal between the two halves.
The top plays no role in the operation of the unit, so I was able to test my modifications without having to reassemble it - very handy.
In this picture you can see the three control switches on the left, and the screw jack assembly that moves the actuator in and out, depending on the fluxgate compass reading. The end of the actuator attaches to the tiller handle, and the body of the unit is fixed to the cockpit somewhere.
Underneath the flexible membrane (in the removable top) of the control panel lies a circuit board containing three spring loaded microswitches that require a 'push and momentary hold' action for normal operation. As per the introduction, one switch engages the automatic course lock mode, and the other two allow for heading adjustments to port and starboard. It was the functioning of these switches that I had to replicate in the wired remote control.
One might think that the natural course of action is to simply solder in three new switches, at the end of a long wire, to parallel the action of the circuit board switches. However, this can lead to problems due to effects like voltage drop and inductive/capacitive influences, possibly rendering the circuit unreliable and perhaps even damaging it. There is also the issue of electrical isolation to consider, in order to prevent accidental coupling of damaging voltages to the autohelm circuitry. Since your life could depend on it, these issues should be carefully considered.
To avoid these problems and provide isolation, I installed small circuit board type microrelays right inside the autohelm housing that allowed me to keep the actual extensions to the original circuitry as short as possible; in this case, about 2 inches of wire was all that was needed. The actual contact arms of these relays have a very low mass and thus they are very fast acting, with a current rating that is well in excess of what is required. Even though the actuating voltage is 12 V from my conventional battery system, I used 24 Volt relays simply because of their availability, and they worked fine. Using the relay approach also allowed the extension wire to the actual remote control housing to be as long as I wanted it, without having to worry about the gauge of the wire.
I then ran the relay actuator control wires out to a chassis connector on the back of the autohelm, so that I would be able to disconnect and remove it easily if it needed servicing (not to mention making the physical installation much easier). I chose a connector and wiring with a number of extra spare pairs in them so that I could add other circuits later if necessary. You can see the connector at the bottom of the picture above.
Allowing enough length to run anywhere in the boat, I then attached it to an inexpensive plastic housing I bought at the local electronics store, and installed several push button switches that would mimic the action of the switches on the autohelm. I also installed two LED indicators that would indicate 'power on' and 'active mode engaged' conditions (see closeup of wired remote control box at left). I didn't bother extending the indicator lights for the port and starboard course adjustments because the autohelm emits a beep sound that can be clearly heard from anywhere on boat when these buttons are activated.
I located the remote in the cabin entry stairway so that it could be reached from either the inside or the outside. This approach provided effective operational flexibility, and I even found that I could reach it from the foredeck without returning all the way back to the cockpit. Now all I had to do was extend it further with a wireless hand held controller, install a pulpit camera so I could see where we were going while I was down below, and get the autohelm retrofitted below decks so that the cockpit was more open for crew use. These issues will be covered as they are developed.