Computer Control

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Computer Control
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Computer Control Basics

• Input (Sensors)
• Processing (Black Box)
• Output (Actuators)

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Computer Sensors

• Voltage Producing Sensors
• Variable Resistance Sensors
• Variable Voltage Sensors

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Voltage Producing Sensors

• There are two common types used in vehicles and
  equipment
• Variable Reluctance Sensors
• Hall Effect Sensors

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Variable Reluctance Sensors

• These sensors often measure Rotation
• They create their own A/C voltage
• They have many names but work the same
• Magnetic Pulse Generators
• Pickup Coils
• Reluctor Sensors

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Variable Reluctance Sensor

• Uses a Reluctor that moves past a coil of wire
  wrapped around a magnet.
• As the reluctor moves the magnetic flux lines,
  A/C voltage is induced in the coiled wire.
• It uses 2 wires and create its own voltage
• Senses speed and position of rotating objects

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Position Sensor

• Output Shaft

Missing teeth identify crankshaft positionOther
teeth measure RPM
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Hall Effect Sensors
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Hall Effect Sensors

• Digital sensor
• Uses 3 wires
• positive voltage, ground and signal voltage
• Senses speed and position
• Can sense very slow rotation speeds

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• Hall Effect Switch

Magnet
3 wiresPower Ground Signal
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A/C Analogue SignalNotice position locator
D/C Digital SignalNotice position locator
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Variable Resistance Sensors

• Thermistor
• Variable Resistor Rheostat Stepped
  Resistor

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Thermistor
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Variable Resistor
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Variable Voltage Sensor

• Potentiometer
• Switches
• Fancy Magical Electronic Sensors

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Potentiometer
Used as a sensor
2 volt
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Potentiometer
Very low current
4 volt
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Switches (Pull-Up)
Biased Low (Signal wire should read ground
volts when unplugged)
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Switches (Pull-Down)
Biased High (Signal wire should read system
voltage when unplugged)
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Computer Actuators

• Relays
• Solenoids
• Stepper Motors
• Indicator Lamps and Display Panels

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Relay
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Relay
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Solenoid
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Normally Closed Solenoid
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Normally Open Solenoid
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Stepper Motor

• Used to control a specific position
• Air Vent
• Cruise Control
• Gauges
• Control Module will Count the steps to know
  what position the motor is in

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Stepper Motors
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6 steps higher
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2 steps lower
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Computer Networks
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Understand the CAN-BUS Electrical System

• CAN stands for Controller Area Network
• This allows all the computers (controllers) to
  talk to each other on one set of wires
• BUS refers to a common wire
• Computers talk to each other on a Network where
  each Controller shares the same voltage signals
  at the same time

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What Language do computers use?

• Digital
• ON - OFF . High - Low 1 - 0
• Binary code is either 1 or 0 known as a bit
• 8 bits in a Byte
• How many bits in a Kilo Byte? Mega Byte? Giga
  Byte? Terra Byte?

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Computers talk fast!

• Hertz Hz
• Mega Hertz MHz
• Giga Hertz GHz

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How do computers talk?

• Voltage
• High Low
• On Off

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What messes up the Communication?

• Open Circuits
• Short Circuits
• EMI
• (Electro Magnetic Interference)

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What Causes Electro Magnetic Interference?

• Radio Waves
• Electrical Current moving in nearby wires

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How can you avoid EMI?

• Twist the communication (BUS) wires
• Use a grounded metal shield that surrounds the
  BUS wires to absorb the energy of moving magnetic
  flux lines

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120?
120?
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How can you test for Opens or Shorts in the
CAN-BUS?

• Use an Ohm Meter
• Should read total parallel resistance of CAN
  terminals 1 2

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120?
120?
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Why do computers need to talk?

• More than one computer may need vital information

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How do you fix Computers?

• Look for proper sensor input
• If the sensor input is incorrect,
  test the sensor and wires
• Look for actuator commands
• If the actuator does not respond test
  the actuator and the wires