Autopilot

The Neco Autopilot is a very sturdy construction. A huge compass is mounted on a "shelf" on the mast (must be high up so the steel hull dosn't affect it). Inside the boat is the manuoverpanel and downunder is the drivemotor with a buildt-in rudderposition indicator.

First step was to re-engineer the Drive motor conections witch gave this complicated physical schema.

I then rewrited the schema from electrical point of view and it got a lot easy circuit to understand. I didn't fully investigate the internal connection of the electrical engine but it's certainly a paralell connection of rotor and stator ("DC shunt motor") as the engine speed is decent low constant speed with a high torque.

Warning! Be sure to have a QUICK way to switch off battry from the Autopilot motor. If you accidentlyswitch off the clutch before you switch off the motor current the engine becomes a serialmotor and will start to wind up to extremly high rpms until it burns in flames and screems!!!

The Autopilots drivemotor is "slow running" at low current but it tries to maintain constant speed during load. During load it could consume up to 30 amp I belive. (I'm not strong enough to break the engine completly! I would like to do some torque measurments...:-)

Below is the present prototype hardware circuit, version 2.0. I did a PCB for the 1.00 version because of the extensive use of surface monted components.

The main source is in place but not fully working yet.
The following routines is working:
- Engages the clutch mechanism - locks the steering wheel.
- Turn left
- Turn right
- Measure rudder position: 12 bits A/D (value 133-499 311 is center)
- Read NMEA compass $IIHDM... Magnetic heading
- Calibration of positions: Center, Max left, Max right
- Stores all parameters in I2C EEPROM

Todo:
+ SeaTalk input. Should understand my SeaTalk remotecontrol.
+ Button steering with +-1 and +-10 degrees
+ Tack function 80-120 degrees, rudder speed and max time compare against speed thrue water and adjust...
+ Voltage measurement, don't work if out of current or if it's consumes to much.
+ Send NMEA rudder position and Compass heading.
+ Parameterhandling: Rudder speed, sensitivity, and some more stuff.

Progress! ( February 2006)

Now I can control the drive unit from the serial terminal (eg. Hyperterm). I get the rudder position and will send that out on the serial NMEA output. I also read the compass direction from my old ST50 Compass unit. Unfortunaly the ST50's Seatalk driver chip ( or something like that - i diassembled it and there is a short inside the chip :-( ) is broken. But the unit works with the NMEA output. Strange, but there is no checksum for the NMEA sentence "IIHDM" - is this because it's a too old protocol version?

March & April 2006

To simplify the electronics I had to rewire the original relays a bit. They are driven with +12V but thats tricky to do when the electronics is based from the same ground but only +5V. So I changed two wires and now the relays always has +12V and on the AP PCB there is two darlington NPN thats sink the relay to ground. Due to the CPU behaivor to set output ports to high during reset/download I needed to add a PNP inverter before the Clutch relay NPN. So now the electronics seems to be very complete.

May 2006

Not much done this month. Except an hour counter and an embryo for the automatic propshaft alternator... a link will be added soon.

June 2006

I bought a brand new Raymarine GPS repeater for 3.5€! It's old but does the reapeater job well. ( Its an 80C32 with 27C256...is that old chip read protected? ;-)

July 2006 is so hot...

August 2006

was to one of the four (?) hottest summers in 100 years! No wonder I'm not welding inside the hull. No progress here either. We bought a Trio 80 and is out sailing!

Thanks for all e-mails! Hope some of my answers could be to any help!

more to come...