Controller for electric drive

One thing that has been bothering me for some time is how to interface our morse control lever with the new electric drive chain. Yesterday I was sent a diagram from  electro-vehicles.eu which helped a lot.

It appears that the engine throttle is controlled by a potentiometer across a 5 volt supply. There are two switches - one for forward and one for reverse.

OK, makes sense but how on earth do you do this on a yacht? A yacht morse controller moves forward to increase throttle and backwards to also increase throttle from a central null point.

For days I have been puzzling thinking of this and then suddenly, very late at night it came to me:

Use a DC:DC converter to create a negative 12 V from the positive 12 V and then use a dual gang potentiometer (attached to the existing Morse controller) so that the centre is 0V and with one track wired inverted. Moving one way will increase volts on one track and moving other way will increase volts on the other track, the diode mixer will mean moving either direction from the centre off will increase voltage to the output.

Only about 20% of the 270 degree track would be used in each direction due to the throw of the Morse controller. For protection, use a 5V zener to ensure it never goes over 5V and a 2 way switch (also attached to the existing Morse controller) to switch between forward and reverse. May need some fiddling of components to get voltages correct for the amount of travel of the potentiometer.

I slept peacefully after realising this and then in the morning woke and realised I could use two op-amps connected to the output of the potentiometer tacks to provide the forward and reverse connection.

But simpler still... when I read my email from Andrea at electro-vehicles.eu... they can program the controller to accept centre null and forward/reverse off the one control. They call this 'wig-wag' in motor vehicles... we call it morse control in yachts!