Autohelm Inboard Autopilots (ST6000 and ST7000 systems) Service ...
Autohelm Inboard Autopilots (ST6000 and ST7000 systems) Service ...
Autohelm Inboard Autopilots (ST6000 and ST7000 systems) Service ...
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<strong>Autohelm</strong>1. ST 6000 Course Computer Circuit DescriptionCircuit diagram Fig. 1.PCB Assembly/Parts List Fig. 21.1 Power SupplyIncoming power is routed to the PCB. via the 'D' connector socket SKI. VI providessuppression against any voltage spikes present on the incoming DC supply whilstD15 protects against accidental reverse connection of the supply. 1C 1 is a 5vregulator with an integral reset function which resets the microprocessor, via Tr9,should the supply voltage be insufficient to maintain regulation.1.2 Microprocessor <strong>and</strong> Program memoryIC2 is an Intel 80C32 microprocessor with 256 bytes of on board Ram. It canaccess up to 32K bytes of programme memory in IC7, via the latch IC6.A Clock Signal for the microprocessor is provided by an 11MHz ceramic resonator(XL1) <strong>and</strong> C15 & C16. Alternatively. XL2 can be used which combines all threecomponents in one package.1.3 Power AmplifierTR23, 24, 25 <strong>and</strong> TR26 are configured to form a power amplifier capable of drivinga motor in four modes:-1. Drive right2. Drive left3. Short circuit motor (Brakes Motor)4. Open circuit motorMode 3 is used to stop the motor quickly by switching Tr23 <strong>and</strong> 25 On <strong>and</strong> TR24<strong>and</strong> 26 Off. Mode 4 allows the motor speed to be measured by switching off all ofthe power transistors.All four modes are controlled via pins 8 <strong>and</strong> 9 of the microprocessor IC2.1.4 Analogue to digital ConverterIC3.4 <strong>and</strong> 9 form a software driven analogue to digital Converter. IC3 <strong>and</strong> 9 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 allowingmeasurement of the discharge time which is directly proportional to the analogueinput. Analogue channels:-IC3 Channel 0 Reset integratorChannel 1 Integrator discharge signalChannel 2 Fluxgate sense AChannel 3 Fluxgate sense B2SeaTalk <strong>Service</strong> Manual
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