The TP10, TP22, TP32 Users Guide says, “The rudder position is captured at the first time initiation of the Autopilot mode. The information is however lost if the unit is turned OFF. Before initiating the Autopilot mode after a power down, you should ensure that the rudder is centered!” From that I guessed that my TP32 counted CW/CCW from that point using the Hall sensors on the little PCB and their magnets on the pulley.
I know for a fact that the rudder position is accurately displayed on my IS40’s “Steering” display. Somehow, someway, my TP32 keeps up with where its pushrod is located and tells my IS40 display where the rudder is located. It is my guess that the TP-32 counts ball drive shaft rotations using the two Hall sensors and magnets that I have seen at the motor end of the ball drive when I had the case open. But, truthfully, I don’t know. It is just electronic magic to me.
My system consists of a TP32 (I actually own two of them, one is a spare. Both have software
version 1.1.03.00), an NSS chartplotter
, A GS25 GPS
unit, and a RS35 VHF
with a HS35 remote
all on a NMEA2000 loop. All that stuff comes along with four IS15 displays, water
instruments, and a Simrad RA772 radar
on a NMEA0183 network that is connected to the NSS. Hanging on the NMEA0183 loop are a number of USB things – a computer, a SignaLink sound card on the Icom
IC-M710, a GPS puck
, and a few other devises with their USB/RS232 converters. As best I can figure, only the TP32 tillerpilot “knows” the rudder angle, so it must be the thing telling the IS40 display. I have no way of monitoring a NMEA2000 loop, so I don’t really know.
Where did you find the circuit diagrams for the TP32? I’d like to have a copy.