Project - Analysis of a practical automotive wiring circuit

1. Identify each of the major elements in the above automotive wiring diagram.

Ans.  a) Battery               b) Ignition Switch                 c) Starter             d) Fuel on off switch

          e)  Ignition coil          f)  Distributer and Breaker                 g) Engine        h) Generator

2.  Explain the purpose and working of any three elements briefly.

Ans. a) Battery - The first purpose of an auto battery is to provide power for starting your vehicle. It also acts as a surge protector for the car's computer and provides power for short-term use of things like lights, stereo, GPS or wipers when the engine is off.

        Working - The two types of auto batteries — flooded and AGM batteries — use lead-acid technology. A typical lead-acid car battery contains plates of lead alternating with plates made up of other materials, all immersed in an electrolyte solution of about one-third sulfuric acid and two-thirds water.

Turning the ignition triggers the acid in the liquid electrolyte solution to react with the active material on the plates (active material refers to any substance in the battery that reacts with the solution to discharge or recharge the battery). This generates a bigger electrical current. The current travels through the starting system in a chain of reactions that cues the engine to start.

   b) Starter - A starter (also self-starter, cranking motor, or starter motor) is a device used to rotate (crank) an internal-combustion engine so as to initiate the engine's operation under its own power.

        Working - The starter motor is responsible for turning the engine over during ignition and allowing everything else to happen. When you turn the ignition on, the starter motor engages and turns the engine over allowing it to suck in air. On the engine, a flywheel, with a ring gear attached around the edge, is fitted to the end of the crankshaft. On the starter, the pinion is designed to fit into the grooves of the ring gear. When you turn the ignition switch, the electromagnet inside the body engages & pushes out a rod to which the pinion is attached. The pinion meets the flywheel and the starter motor turns. This spins the engine over, sucking in air (as well as fuel). As the engine turns over, the starter motor disengages, and the electromagnet stops. The rod retracts into the starter motor once more, taking the pinion out of contact with the flywheel and preventing potential damage.

     c) Engine - The engine is the heart of your car. It is a complex machine built to convert heat from burning gas into the force that turns the road wheels.

      Working - Internal combustion engines create energy by burning a fuel-air mixture under pressure inside the cylinder, and it's converted into movement by the engine's pistons, connecting rods and crankshaft.A car engine is an intricate machine that converts fuel into motion through a series of precisely timed actions, called strokes. Let’s explore the different strokes which would help us understand this process in detail.

Here’s a step-by-step breakdown of the four strokes of the engine and how they work together:

1. Intake Stroke

• The engine begins by drawing in air, a vital component for the combustion process

• An air filter ensures that the incoming air is clean and free from contaminants

• The throttle regulates the amount of air entering the engine, adjusting it according to the driver’s acceleration demands

2. Compression Stroke

• With the intake of air, the piston moves upwards, compressing the air within the cylinder

• The compression ratio is defined by the space within the cylinder when the piston is at its lowest point compared to when it’s at its highest point

• This ratio impacts engine efficiency and power

3. Combustion Process 

• In petrol engines, the spark plug generates a spark to ignite the air-fuel mixture when compressed

• Diesel engines rely on the heat generated during compression to ignite the diesel fuel

4. Power Stroke

• As the ignited air-fuel mixture expands rapidly, it creates high-pressure gases

• These gases exert force on the piston, pushing it down within the cylinder

• This piston movement generates mechanical power which helps turn the engine’s crankshaft

5. Exhaust Stroke

• After the power stroke, exhaust valves open to release the burnt gases from the cylinder

• The expelled gases travel through the exhaust system, which includes a catalytic converter to reduce harmful emissions

6. Repeat

• These four strokes – intake, compression, combustion, and exhaust – are repeated continuously in each cylinder

• The synchronised actions of multiple cylinders create a constant and smooth power delivery that propels the vehicle

3. If the total load is 10A from the battery, what should be the fuse rating?

Ans: To select the right amperage of the fuse, you first need to know the full-load steady-state current of the circuit at an ambient temperature of 25o C (68o F). Once the current value is determined, then a fuse rating should be selected to be 135% of this value (taken to the next standard value).

For example, if the normal steady-state current is calculated to be 10 amps, then a 15A fuse rating should be selected [10 amps x 135% = 13.5 amps, the next larger standard size is 15A].

The basic rule of thumb is that the voltage rating of the fuse must always be higher than the voltage rating of the circuit that it is protecting.

4. If 500W is the load, what is the voltage and capacity of the battery you recommend?

Ans:

Given:

500W is the load

12V is the battery voltage  (given in the hint)

The capacity of the Battery is Ah = I*t

Power is Wh = V*I*t 

If (V*I*t)/V = I*t = Capacity of the Battery

therefore, the Capacity of the Battery = 500/12 = 41.67Ah

So, the capacity of the battery must be more than 42 Ah, For 5 hours backup capacity should be 42*5 = 210 Ah

5. Identify any two elements which are connected parallel to each other. Why are they connected in parallel?

Ans: Tail Stop Light, Beam Light, Sealed Beam, Parking Light and Horn are connected in Parallel to each other.

They are connected in parallel to each other to get their rated voltage so that they function efficiently. They have their independent switch to control them. If one gets faulty, it doesn't affect the other.

6. Identify any two elements which are connected in series. Why are they connected in series?

Ans: Dome Light and Dome Light Switch, Ammeter, Ignition switch and Current and voltage regulator are connected in series.

They are connected in series for the same current to flow through them. The current has only one path. If one gets faulty, the current doesn't flow further.