Autohelm Inboard Autopilots (ST6000 and ST7000 systems) Service ...

Autohelm1. Course Computer PCB Circuit Description;-Circuit diagram Fig. 1.PCB assembly/parts list Fig. 2.1.1. Power SuppliesIncoming power is routed to the PCB via the 'D' connector plug PL1. VI providessuppression against any voltage spikes present on the incoming DC supply whilst D6protects against reverse connection of the supply. 1C 1 is a 5V regulator and canalso reset the microprocessor, via TR9, should the supply voltage fall below 6V.TR17, C19, D13, R92 and R91 form an 8V regulator to supply the windvane.1.2. Microprocessor and Program MemoryIC2 is an Intel 80C32 microprocessor. It can access up to 32k bytes of programmemory (IC7) via the latch IC6. A clock signal for the microprocessor is provided byan 11 MHz ceramic resonator (XL1) and associated capacitors C15 and C16. C14,18 and 17 provide decoupling.1.3. Analogue to Digital ConverterIC3,4,5 and 9 form a software driven analogue to digital converter. IC3 and IC9 are 8channel multiplexed analogue switches routing all analogue signals, (see tablebelow), through to IC4 which is configured as an integrator. C9 is discharged at aconstant rate triggering the comparator IC5 as it reaches a level of approximately0.53V. The output of the comparator is connected to the microprocessor thusmeasuring the discharge time which is proportional to the analogue input.Analogue Channels;-IC3 Channel 0 Reset integratorChannel 1Integrator discharge signalChannel 2Fluxgate sense AChannel 3Fluxgate sense BChannel 4 Motor Feedback 1Channel 5 Motor Feedback 2Channel 6 Windvane sense 1Channel 7 Windvane sense 2IC9 Channel 0 Alarm sense 1Channel 1 Alarm sense 2Channel 2Rudder ReferenceChannel 3Supply MonitorChannel 4Rate Gyro senseChannel 5Gyro Compass senseChannel 6JoystickChannel 7Not used2SeaTalk Service Manual