Computer Control

Computer Control Basics

• Input – (Sensors)

• Processing – (Black Box)

• Output – (Actuators)

Computer Sensors

• Voltage Producing Sensors

• Variable Resistance Sensors

• Variable Voltage Sensors

Voltage Producing Sensors

• There are two common types used in vehicles and equipment

• Variable Reluctance Sensors

• Hall Effect Sensors

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

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 it’s own voltage

• Senses speed and position of rotating objects

Missing teeth identify crankshaft position

Other teeth measure RPM

Output Shaft

Position Sensor

Hall Effect Sensors

Hall Effect Sensors

• Digital sensor

• Uses 3 wires

• positive voltage, ground and signal voltage

• Senses speed and position

• Can sense very slow rotation speeds

3 wiresPower Ground Signal

Magnet

Hall Effect Switch

A/C Analogue Signal

Notice position locator

D/C Digital Signal

Notice position locator

Variable Resistance Sensors

• Thermistor

• Variable Resistor Rheostat Stepped Resistor

Thermistor

Variable Resistor

Variable Voltage Sensor

• Potentiometer

• Switches

• Fancy Magical Electronic Sensors

2 volt

PotentiometerUsed as a sensor

4 volt

PotentiometerVery low current

Switches (Pull-Up)

Biased Low (Signal wire should read ground volts when unplugged)

Switches (Pull-Down)

Biased High (Signal wire should read system voltage when unplugged)

Computer Actuators

• Relays

• Solenoids

• Stepper Motors

• Indicator Lamps and Display Panels

Relay

Relay

Solenoid

Normally Closed Solenoid

Normally Open Solenoid

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

Stepper Motors

6 steps higher

2 steps lower

Computer Networks

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

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?

Computers talk fast!

• Hertz Hz

• Mega Hertz MHz

• Giga Hertz GHz

How do computers talk?

• Voltage

• High – Low

• On – Off

What messes up the Communication?

• Open Circuits

• Short Circuits

• EMI

• (Electro Magnetic Interference)

What Causes Electro Magnetic Interference?

Radio Waves

Electrical Current moving in nearby wires

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

120 120

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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Why do computers need to talk?

• More than one computer may need vital information

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