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
Position Sensor
Output Shaft
Missing teeth identify
crankshaft position
Other teeth measure RPM
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
Hall Effect Switch
Magnet
3 wires
Power Ground Signal
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
Potentiometer
Used as a sensor
2 volt
Potentiometer
Very low current
4 volt
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
120
120
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