Project - Analysis of a practical automotive wiring circuit

1) Major elements of the automotive wiring diagram are:-

- Battery

- Starter

- Ammeter

- Fuse

- Current and Voltage Regulator

- Generator(Alternator)

- Ignition Switch

- Ignition coil

- Distributor

- Junction Blocks

- Foot Selector Switch

- Parking Lamp, Scaled Beam, Horn, Fuel Gauge, Beam light, Horn Button, Tail stop light switch, Dome Light, Dome light switch, Plate light

2) (i) Generator - In an Automotive circuit the generator type used is an Alternator (AC Generator). It is used to charge the battery and power the electrical system while the engine is running. The alternator produces an alternating current which is then rectified to a Direct Current using a diode. An Alternator converts mechanical energy into electrical energy. It consists of a Rotor and a Stator., the rotor is free to rotate inside the stator.

- The mechanical energy is obtained in the form of rotation from the engine drive belt and is used to move the rotor. The rotor consists of an electromagnet (aka Field) and fits inside the Stator.

The Stator consists of conductor windings in which a voltage is induced due to the rotating magnetic field of the rotor as per Faraday's Law.

(ii) Battery - It is a series and parallel combination of cells, that is used to store electrical energy in form of chemical energy. The chemical reactions within the battery result in the flow of electricity in the circuit.

- It consists of an Anode (Negative or Reducing Electrode), a Cathode (Positive or Oxidizing Electrode) and an Electrolyte that helps in the transfer of ions between the anode and cathode. When connected the Anode gets oxidized in the electrochemical reaction and therefore releases electrons to the external circuit, whereas the cathode gets reduced in the same reaction and gains the electrons released by the anode. We place the load in between to utilize the energy of the electrons from the electrochemical reaction.

(iii) Fuse - It is a basic safety device to protect the users and the equipment when there is a flow of high current, for example in case of a short circuit.

- It consists of a thin wire rated according to the particular ampere value, connected in series to the load. If the circuit tries to pull more than the rated current, the fuse wire melts thus opening the circuit and stopping the current flow.

Nowadays, we use Contactor-Relay arrangements in Automotive systems. Here the relay identifies the fault and the contactor opens and closes the circuit as per the command received.

3) Fuse rating should be in accordance with the total load in the circuit. Generally, the fuse rating is taken as 1.2 to 1.35 times the total load, taken to the next higher rating.

so the fuse rating should be 15 Amps.

4) Power = Voltage * Current

Given, a load of 500 Watts.

Taking battery voltage as 12 V.

So the current requirement is 500/12 = 41.7 Amps

Capacity = Current * Time

capacity = 41.7 Ah

5) The lights are connected in Parallel because a parallel connection means that the same voltage passes through them and they can draw the current as per their resistance value. If they were connected in series the current would face the resistance one after the other and the lights will be less bright.

6) Fuel gauge and Fuel tank are connected in Series. The sensor in the fuel tank varies its resistance in accordance with the fuel level which causes a change in the current flowing through. This change is read by the fuel gauge and the needle shifts its position corresponding to the current.