Unit 5

Horn Switch

Cars are usually fitted with a high-frequency (HF) or windtone horn as standard equipment,

normally located behind the front grille. A vibrating diaphragm makes the sound in both types.

The diaphragm is moved by an electromagnet and contact breaker, like that of an electric bell. In

an HF horn, a resonator plate is fixed to the diaphragm to amplify the sound. In a windtone, the

diaphragm makes air vibrate in a trumpet, giving a lower pitched and more musical sound. The

length of the trumpet fixes the pitch. In some cars there is a pair of wind-tones, tuned to give two

notes. They are marked for low notes and 'H' for high. A third type of horn, the air horn, uses a

compressor, and is fitted only as an accessory. It has a loud and distinctive note and is sold with

fitting instructions. Note that an audible warning device is a legal requirement for all vehicles, and

strident horns sounding fluctuating notes are allowed on emergency-service vehicles and police

cars only. The horn may be operated by a stalk on the steering column or a button in the centre

of the steering wheel. The stalk is wired to a multi-pin connector

Dipper Switch

Auto Dipper, a device or system, designed and developed to overcome the common problem for driving at night on highways. The system consists of one sensor to measure the intensity of light and an electronic circuit to control the shifting switch of the beam light.

Main functions of the device are:

(I) headlight beam shifting (high/low beam) after sensing the light of vehicle approaching from opposite direction;

(II) (Giving stay on left (i.e. Don’t overtake) signal to the vehicle following.

DESCRIPTION OF THE DEVICE:

The size of the device is about 2.5 inches cube.

Auto dipper box can be installed anywhere near steering as per convenience so that "ON-OFF" switch on auto dipper box can be used easily. Sensor Eye is mounted near wiser position near the top edge of wind screen (inside the car) such that it receives the light of the approaching vehicle in proper position. Sensor position can be adjusted slightly by bending the sensor support. The device gets activated only when headlights are in "on" position. For truck & buses, Sensor Eye can be placed on lower side of wind shield inside close to the right hand of driver and for car and jeep etc. the Sensor Eye can be placed using the Sun wiser support screws. The device can be operated with the existing 12 volts battery of the vehicle.

FUNCTIONS

Auto Dipper keeps the head light in "High" beam if there is no vehicle from opposite direction. While crossing, first momentary dip is given by the vehicle fitted with the auto dipper automatically when the two vehicles are at a distance of about 120 meters.

Low beam continues till distance between the two is reduced to about 90 meters than this vehicle shifts to "High" beam, which continues till the two vehicles are 30 meters apart. Now the vehicle fitted with auto dipper automatically shift to "Low" beam and continues in the "Low" beam till the two vehicles cross each other.

TECHNICAL SPECIFICATIONS OF THE PRODUCT:

Voltage : 12 Volts

Contact Current

: 20 Amps

Device Wattage

: 1 watt

Sensitivity range

: (Adjustable from 0.5 lux to infinity)

Auto dipper can be used

for vehicle with headlight.

: rating upto 250 watts.

Push Pull Solenoid

Refer Class notes

Toggle Switch

Toggle Switches are reliable and durable switches that are familiar to mostly everyone. First

introduced in 1916, the toggle switch that may first come to mind is your typical light switch.

Toggle switches, however, have many uses, both residential and commercial. Several

accessories have also been designed for toggle switches, everything from safety covers to

prevent accidental actuation to boots that will protect them from the elements. Whether your

toggle switch is illuminated, heavy-duty, or recessed, it will provide years of safe and dependable

use.

Toggle switches come in nylon or metal, and sealed or unsealed actuator styles. It also carries a heavy duty toggle switch design available when extra high amp rating is needed. The reversing toggle switch is a DPDT control for motors and can be connected with back-up alarms. A completely sealed toggle switch with weather resistant plastic coating can be used for marine and heavy duty equipment applications. Pair toggle switches with other components that handle harsh environments, such as marine rated circuit breakers.

Flush Switch

Flush LED Switches combine styling and functionality with an illuminated LED ring inset on a clean stainless steel shell. Available in Momentary (Push Hold On, Release Off) and On / Off.

Each switch can handle 3A of current. The switch diameter is 16mm (0.63") and sit almost

completely flush to the mounting surface. These switches are available in a variety of colors.

Limit Switch

A limit switch is a switch operated by the motion of a machine part or presence of an object.

They are used for control of a machine, as safety interlocks, or to count objects passing a

point. A limit switch is an electromechanical device that consists of an actuator mechanically

linked to a set of contacts. When an object comes into contact with the actuator, the device

operates the contacts to make or break an electrical connection. Limit switches are used in a

variety of applications and environments because of their ruggedness, ease of installation, and

reliability of operation. They can determine the presence or absence, passing, positioning, and

end of travel of an object. They were first used to define the limit of travel of an object; hence the

name “Limit Switch.”

Standardized limit switches are industrial control components manufactured with a variety of

operator types, including lever, roller plunger, and whisker type.

Ignition Key & Lock

The ignition switch, usually located on the steering column, has a "hot" wire (or a direct

connection to the battery), which routes current to the starter solenoid. The starter solenoid can

be located inside or adjacent to the starter motor. Sometimes there is a starter relay that opens

this circuit and is activated by the ignition switch. A relay is a way that one circuit may be

controlled by the current from a separate circuit. The starter solenoid is essentially a large relay

itself. When the ignition switch is open, a small amount of current is delivered to the starter

solenoid, which then opens the circuit that operates the starter motor.

This circuit uses a tremendous amount of current. This function of the starter solenoid is

accomplished by means of a coil and plunger within the solenoid. When current flows through the

coil, it creates a magnetic field, which pulls the plunger down. A metal disc attached to the

plunger then makes contact between two terminals which connect the battery directly to the

starter. In addition, most starter solenoids will also cause the small gear on the starter motor to

mesh with the teeth in the engine flywheel, thus allowing the starter to crank the engine.

Problems with the ignition switch can result in a no-start situation (starter motor fails to turn) or

the starter motor may fail to stop when the key is released from the start position. This may be

because the contacts in the switch have been worn or burned.

Solenoids, Relays

Notice in the above diagram that a relay uses an electromagnet. This is a device

consisting of a coil of wire wrapped around an iron core. When electricity is applied to

the coil of wire it becomes magnetic, hence the term electromagnet. The A B and C

terminals are an SPDT switch controlled by the electromagnet. When electricity is

applied to V1 and V2, the electromagnet acts upon the SPDT switch so that the B and

C terminals are connected. When the electricity is disconnected, then the A and C

terminals are connected. It is important to note that the electromagnet is magnetically

linked to the switch but the two are NOT linked electrically.

There is another type of relay called a solenoid that basically works on the same

principle. The solenoid electromagnet consists of wire wrapped around a tube

containing an iron cylinder called a "plunger". When electricity is supplied to the wire

coil, the "plunger" moves through the tube and activates a switch. As is the case with

many mechanical devices being replaced by their electronic equivalents, relays are

being "phased out" by Solid State Relays (SSR's). Mechanical relays do have

their disadvantages when compared to an SSR

1) switching is much slower

2) the contacts wear out

3) they make noise when they switch

4) their magnetic fields can cause problems for nearby components

Presently, their one advantage is their ability to switch high voltage and high

current circuits. (the automobile starter solenoid for example). No doubt with time, even

this will be surpassed by the SSR. At least mechanical relays can easily demonstrate

the principles of electrical/electronic switching.

When the ignition key is turned all the way to the "start" position, it allows electricity to flow to the

starter solenoid (relay) which then connects the battery to the starter motor.

Contact Less Switches

Refer Class Notes