Project - Analysis of a practical automotive wiring circuit

1. The major elements in the above diagram are:

• Ammeter
• Starter
• Battery
• Breaker
• Ignition coil
• Distributor
• Generator
• Current and Voltage regulator
• Foot selector switch
• Fuel Guage
• Switches
• Fuse

2.

1)Battery:

Purpose:

The main purpose of a battery is to start the vehicle. The battery provides electricity to the starter motor which can crank the engine running. The secondary purpose of the battery is to power all the accessories in a vehicle. For example: Headlights, indicators, audio system, naviagtion etc., The battery is also used to store excess electricity produced by the alternator to prevent damage.

Working:

Most of the batteries used in the ICE cars are 12V lead acid batteries. There are two cycles in a battery namely charging cycle and discharging cycle. The battery consists of an anode, cathode and an electrolyte. After charging cycle, electrons gets builded up in the anode. This causes a potential difference between the anode and cathode. But electrons cant escape to the cathode due to electrolyte. When we connect an extrernal load to create a closed circuit, electrons travel to the cathode until the equilbrium is achieved. Once a specific amount of electrons reached the cathode, the electrochemical reaction prevents all the electrons to reach the cathode. So the battery will not be fully discharged to maintain the minimum voltage. Once we charge the battery again, the anode and cathode will be restored to their same chemical state and can be used again.

2) Starter:

Purpose:

The purpose of the starter motor is to crank the engine, so it can run on its own power. IC engines cant start on its own. As soon as the engine runs on its own, the starter will stop.

Working:

The Starter motor used in cars and bikes are usually 12V DC motors. When we start the ignition, the solenoid in the motor gets excited by the power from the battery. The electromagnet in the motor pushes a rod with a pinion. The pinion makes contact with the flywheel where the gears in the pinion starts turning the flywheel. The starter motor will turn the flywheel for one or two rotations until the engine starts. Once the engine starts, the power to the starter motor will be disengaged resulting in no electromagnetic field causing the rod to retract. This will prevent potential damage to the flywheel and the starter motor.

3) Breaker:

Purpose:

The breaker is basically an electric switch. The circuit breaker prevents the electrical circuits in the vehicle from overload or unwanted loads and current. The circuit breaker will open the circuit if its detects any malfunction to protect the components.

Working:

The circuit breaker usually have moving and fixed contactors. When the circuit is closed and in normal condition, the contactors will touch each other resulting in electric flow. The contactors are activated with the help of a spring. If the circuit breakers detects a malfunction from any of the components due to faulty current, the spring gets energized and the circuit will be opened. The circuit will be open because the contactors are no longer touching each other. This will prevent damage to the circuit and the components.

3. Given:

Load = 10A

Solution:

Lets consider this load is for a automobile battery

Typical Automobile battery voltage = 12V

Power = V x I

P = 12 x 10 = 120 watts

Fuse rating of any appliances should be 25% higher than the Actual load

That means the fuse rating should be 125%

P = 120 * 125 / 100

P = 150W

I = P / V

I = 150 / 12

I = 12.5A

Therefore the fuse rating should be 12.5A

4.

Given :

Load = 500W

To find :

Recommended battery voltage and capacity

Solution:

The common battery voltage for small load applications is 12V

Therefore the voltage recommended for this load is 12V

From the given data,

P = V xI

500 = 12 x I

I = 500/12

I = 41.67A

For a running time of 1hr, the capacity can be calculated by

Time = Capacity / Current

1 = Capacity /41.67

Capacity = 41.67Ah

Therefore for the 500W load to run continuously for 1 hour, we need a 12V battery with a capacity of 41.67A

In terms of commercial available batteries, we can choose a 50Ah battery.

5. Series connections:

The battery and the starter motor are connected in series with each other.

Reason:

Because starter motor requires peak current. If its connected in parallel with other components, battery cannot provide enough current to the starter motor. Hence battery and starter are connected in series to get enough ampheres of current.

6. Parallel connections:

The two tail stop lights are connected in parallel with each other in the above diagram.

Reason :

The two tail lights are connected in parallel because the lights always have the same voltage rating. If the bulbs are connected in series in case of any one of the light is malfunctioning, both lights will not glow. So we need to connect the tail stop lights in parallel.