GUJARAT TECHNOLOGICAL UNIVERSITYAhmedabad

Seminar entitled on

Warning & alarm instruments

By:

D v Dhanak Enroll. No. 140280711007 1

Warning & alarm instruments

In order to keep driver informed about correct operation of engine and other system

Brake actuation warning systemDeveloped in Israel in

1989 which display additional signaling information for driver.

may indicate a fault in the braking systemThe brake warning light is located on the instrument.

Brake actuation warning system Primary Function:1) The parking brake or service brake is engaged2) The level of brake fluid that is present in the braking system3) The amount of wear on brake pads and linings4) faulty switch on the service or parking brake.

Brake actuation warning systemBrake pedal position sensor: Brake Pedal is up and both Reed Switches are

closed, Rear brake lights off .Brake Pedal is depressed, Reed Switches open activating rear brake lights

Brake actuation warning systemBrake fluid level sensor: To measure fluid level capacitive position sensors are used. It sense the liquid level in reservoir by measuring changes in capacitance

between conducting plate which are immersed in liquid

Brake actuation warning system

Brake actuation warning system

Flash systemFlashing lights are permitted on vehicles as follows:Gaining attentionTo indicate an intention to turn or move to the right or

leftBimetal type mostly used

Flash system

Flash system

Flash systemA flasher unit produce the fluctuations of current to cause the lamps to flash

on and offThe flashing rate of the lamps is between 60 and 120 flashes per minuteTurn indicating switch is self cancelling to pass current either right or left

sideCurrent flows from the battery to terminal B, to armature C, to the hot wire,

to the ballast resistance, to contact D, to the iron wire coil around the iron core, to terminal L, to the turn indicator switch, to either the left or the right-hand pair of flashing lamps

The lamps do not light because the ballast resistance limits the size of the current

Oil pressure warning systemThis light should come on briefly as the engine is started. If it does not come on, have the vehicle serviced by your dealer. If the light comes on and stays on, it means that oil is not flowing

through the engine properly. e.

Oil pressure warning system Wheatstone bridge is used to measure changes in pressure . Two series circuits connected in parallel across a power supply. 3 of the resistors are kept at exactly the same value and the fourth is the sensing resistor. When all four resistors have the same value, the bridge is balanced and the voltage sensor will

indicate a value of 0 volts. The output from the amplifier acts as a voltmeter. If there is a change in the resistance value of the sense resistor, a change will occur in the

circuit’s balance. The sensing circuit will receive a voltage reading that is proportional to the amount of resistance change.

Engine overheat warning system The vehicle as an indicator to warn of the engine overheating. This light comes on briefly while starting the vehicle. If the decision is made not to lift the hood when this warning appears, get

service help right away. If the decision is made to lift the hood,

make sure the vehicle is parked on a level surface.

Engine overheat warning systemThermistor : Thermistors are used to measure the temperature of liquids and air. A thermistor is a solid-state variable resistor made from a semiconductor material,

such as metal oxides When the temperature of the engine increases. the resistance of the thermistor

decreases is screwed into the bottom of the coolant outlet on the cylinder head . It providing

the signal for The coolant temperature gauge, Overheat signal to the A/C system to shut off the compressor, Overheat signal to the Auto-Check system to warn the driver,

Engine overheat warning system Thermistor used in this circuit, as beads heat resistant. Thermistor is connected to R1 for divide the voltage of the power supply. This

voltage will decrease as the temperature rises.IC1 will be switch close makes has voltage at output pin 6 to send .

The IC2 is connected as an stable multi vibrator to the sound signal generator circuit .The VR2 will determine the frequency of the sound.

Used in this circuit currents up to 10 mA.

Air pressure warning systemAir pressure monitoring system is an electronic system designed to

monitor the air pressure inside the pneumatic tires on various types of vehicles

PMS was first adopted by the European market in the Porsche 959 in 1986, using a hollow spoke wheel system.

Improved safety Under-inflation Reduced maintenance

Air pressure warning systemDirect TPMS: Direct TPMS employ pressure sensors on each tire, either internal or external. IT measures the tire pressure in each tire and measure under inflation. PCB — to get the sensor module that is mounted to the valve stem inside the tire: pressure sensor; antilog-digital converter; microcontroller; system controller; oscillator; radio frequency transmitter; low frequency receiver First-generation dTPMS sensors that are integral with the valve stem have suffered

from corrosion. Metallic valve caps can become seized to the valve stem because of galvanic

corrosion of dissimilar metals, and efforts to remove it can break the stem, effectively destroying the sensor.

Air pressure warning system

Air pressure warning systemIndirect TPMS It do not use physical pressure sensors but measure air pressures by

monitoring individual wheel rotational speeds . ITPMS systems are based on the principle that under-inflated tires have a

slightly smaller diameter (and hence higher angular velocity) than a correctly inflated one. These differences are measurable through the wheel speed sensors.

Speed warning systemThis systems help drivers to keep their speeds within the recommended

limits.The speedometer is to indicate the speed of your car in miles per hour,

kilometers per hour.

Speed warning system sensors work according to the magneto resistive principle.( magneto resistance is the

property of a material to change the value of its electrical resistance when external magnetic field is applied to it) Magnetic resistance is known as reluctance (variable reluctance = VR).

Each tooth positioned in front of the pole decreases reluctance and increases magnetic field density around the coil

Each valley increases reluctance and causes the magnetic field to collapse around the coil thereby generating a voltage.

create a sinusoidal electrical output signal.

Speed warning system They have three wires: for power supply, earth and a signal. A rotating magnetic element with alternating north/south/north/south polarity in

conjunction with a sensor ring creates a digital signal for the ECU – this is how it is able to calculate wheel speed.

Door lock indicators

Door lock indicator also known as "dome light" (or "courtesy light") It is located in or near the ceiling of the passenger compartment,

available inputdoor sensor: open (magnet)/close

car engine: ignition on/offdesired output light!

Door lock indicators

Door lock indicators Car courtesy light switch

A. When switch 1 closes, the lamp lights and the capacitor starts to charge then current flows in the BJT's base to switch on the BJT, relay contacts open, lamp switches off. Open switch 1 and close switch 2 to let capacitor discharge. Open SW2 and close SW1 to recommence.B. Courtesy lightingThis was the basis for some automatic courtesy lighting circuits used in motor vehicles, opening the door operated SW1, turning on the ignition switch operated SW2. Thus, the lights stay on long enough for the driver to insert the ignition key in the ignition lock. Opening the door with the engine running may not turn on the courtesy lights unless another circuit is used, or perhaps SW2 is operated by the starter motor solenoid, but then the capacitor will stay charged after the door closes, a bleed resistor, say 100 k ohm to 1 M ohm, across the capacitor could fix that.