Project - Analysis of a practical automotive wiring circuit

1. Major elements in automotive wiring diagram:

1. Generator (connected to engine)
2. Fuel or Gas tank
3. Fuel gauge
4. Ignition switch and coil
5. Spark plugs
6. Distributor
7. Battery
8. Starter
9. Voltage and current regulator
10. Ammeter
11. Breaker
12. Fuse
13. Foot selector switch
14. Switches
15. Lights & Horn

2. Battery:

Battery is basically an energy storage device. It stores energy in chemical form. A battery is an electrochemical device consisting of cells connected in series or parellel combination as per the requirement. There are two types of batteries, one is primary batteries and other is secondary batteries. Primary batteries are non-rechargable, once the charges are discharged it will be useless and discarded. While, secondary batteries are rechargable. Battery supplies only DC voltage. A battery consists of two terminals or electrodes positive (cathode) and negative (anode) and electrolyte (liquid medium). When the DC load is connected across the two terminals through an external circuit, the electrons will flow from anode to cathode and the current flows in the reverse direction. During this, to balance the flow of electrons, charged ions also flow through the electrolyte solution. Thus, this cause the potential difference across the two terminals and provides electric current.

Ignition coil:

It is more or like a step up transformer. The purpose of ignition coil is to increase the battery supply voltage and distribute it to the spark plugs. Beause spark plugs requires more voltage to create a spark. It consists of a primary winding and secondary winding. When the ignition coil primary winding gets the supply voltage from the battery, a magnetic field is produced. The secondary winding has more turns than the primary winding and thus the magnetic induction causes the voltage to be doubled or tripled in the secondary winding as per the requirement.

Fuse:

Fuse is an electrical safety device consists of a conductive wire that is designed to melt and seperate in the event of current surge.

3. Given:

Total load current = 10 A

To find:

Fuse rating

Soln:

Since, the optimum current is 10 A, the fuse rating should not be below than this.

For a normal or ambient temperature, lets take standard fuse rating, 25% > optimum current,

therefore, Fuse rating = 10 + 10 x (25/100)

= 12.5 A

4. Given:

500W is the load

To find:

Recommended voltage and capacity of battery

Soln:

Since it is given to consider battery voltage as 12V (because automotive electrical accessories uses minimal power).

Then, the current required would be = 500/12 = 41.67 A

I would choose the minimal capacity, 41.67 Ah because 10 A is the total requirement.

5. Generator and voltage-current regulator are connected in parellel, because the voltage regulator has to detect the same exact voltage as generated by the generator. So, by connected in parellel, the voltage across the both is same.

6. Battery and starter are connected in series. Also with horn. Because, it requires constant current for the operation.