Project - Analysis of a practical automotive wiring circuit
- 1). Battery, Starter, Generator, Junction block, Ignition coil, Distributor, Breaker, regulators, sealed beam lamp units, gates, fuel on/off , Ammeter ,lights, switches, Tail stopper, Gas tank unit, horn, foot selector switch, fuses, fuel cut off switch buttons.
i) The purpose and working of Battery;
Purpose:
Batteries and similar devices accept, store, and release electricity on demand. Batteries use chemistry, in the form of chemical potential, to store energy, just like many other everyday energy sources.
- The primary functions of battery in automotive engines are to power the starter motor so as to run the engine.
- All electrical components in a vehicle rely on the battery.
- In modern cars where most parts like the injector system, spark plug, sensors are also powered by the battery
The applications of battery in gasoline and diesel internal combustion engines. Their category of battery is referred to SLI batteries, serving the purpose of starting, lighting, and ignition on vehicles. while starting the engine, the SLI battery types supply the extra power necessary when the electrical parts in a vehicle require excess power above the supply of the charging system. This feature can also be called a stabilizer.
Special types of battery are used to power electric and hybrid cars. they use high-voltage electric vehicle battery, but the automotive battery can also be used as well. This allowed the used of standard automotive electrical parts that are designed to run on 12 volts. These types of battery are also called auxiliary batteries.
The electric vehicles (EVs) don’t charge the auxiliary batteries like the conventional internal combustion engines that use the alternator to boost their batteries while running. electric vehicles use a DC-to-DC converter to controls the voltage to the required float-charge voltage.
Working :
the working of automobile batteries is less complex and interesting. Most of it relies on a lead-acid chemical reaction to power the electrical components. The SLI is the type mentioned, it provides short bursts of energy in order to power the accessories, and importantly the engine starter motor. It starts the battery and as soon as the engines begin to run, alternator returns charge to the battery.Just imagine a battery as a power plant that converts a chemical reaction into electrical energy.
Typically, SLI batteries have six cells, containing two plates at each. One of the plates is made of lead and the other with lead dioxide. Each cell can produce about 2-volts of energy. The plates are submerged in Sulphur acid that allows the two plates to react. This acid will trigger a reaction on the lead dioxide plate causing it to create ions and lead sulphate.
The irons created by the lead dioxide plate react to the other plate to produce lead sulphate and hydrogen. This result in a chemical reaction that produces electrons, the electrons move around the plates and generate electricity. The electricity flows out through the terminals to start the car and power other electrical components of the car.
The battery can be jumpstart because the chemical reaction process is entirely reversible. This is why the engine alternator can continue to charge the engine throughout the duration of its life.
ii). The purpose and working of starter;
Purpose: A starter or starter motor is an electrical device that used to rotate (crank) internal combustion engines so as to initiate the engine’s operation under its own power. As soon as the engine begins to run, it got disconnected from the engine, which now relies on the combustion process. The component is mounted on the engine’s gearbox housing, and the starter motor gear meets flywheel’s teeth.
Being an electrical component, a starter consists of a powerful DC (Direct Current) electric motor and a solenoid. The solenoid receives positive power direct from the battery and hearth current from the engine body. In order to turn the engine, a 12-volt battery must be used to run the starter. This means the battery has to be sufficient enough to power the device. In the most situation where the starter motor clicks but won’t start, the issue is either from the battery or starter itself.
The starter motor has only one function which is the first and second rotations the engine needed. Apart from that, the device is just an extra load to the vehicle. There should be another means of starting vehicles without starter motors right! I think the component is too big for one function.
Most drivers improvise if the starter is faulty or battery power is low. The improvising is done by pushing the vehicle back or from just to begin the combustion process. Though this is not highly advisable, but in a situation where the battery needs to be charged by the vehicle’s alternator. We can discuss on the starter motor function and your experience improvising in the comment section.
Working of starter:
The working of a starter is quite easy and interesting, but most drivers really don’t know the secret behind motor cranking. When the ignition key or bottom is press, the transmission should be in park or neutral state. The battery voltage goes to through the starter control circuit to activates the solenoid.
The starter motor is powered by the solenoid, which helps to push the starter gear forward to mesh with the engine flywheel. This flywheel is mounted on the engine crankshaft, so as the starter motor spins it turns the `flywheel so as the crankshaft. As soon as the engine start, the system disengages from the flywheel.
Note in an automatic transmission, starter motors can only be operated when the vehicle is in park or neutral position. And in manual transmission, the clutch pedal must be depressed.
The working inside the starter motor, there are four field windings attached to the housing from inside. The armature (rotating parts) is connected through the carbon brushes in series with the field coils. But remember in some starters field coils are replaced with magnet fields. There is a small gear at the front of the armature attached with an overrunning clutch.
iii) the purpose and workings of Ignition coil;
Purpose: The air-fuel mixture is ignited in the combustion chamber by an ignition spark. In order for the spark plug to produce the spark, an ignition voltage of approx. 30,000 Volt is required. This voltage is generated by the ignition coil from the 12 Volt voltage of the vehicle electrical system and transferred to the spark plug at the moment of ignition.
The ignition coil acts like a transformer. By means of two coils, one inside the other, the ignition coil transforms the electrical energy from the vehicle battery into high voltage, saves it briefly and then emits it as a high voltage current pulse to the spark plug.
workings of Ignition coil;
A voltage is passed through the primary windings (from the battery (+ve), via the ignition switch, through to ground (–ve)) a magnetic field (flux) is generated around the windings. If the voltage is interrupted (switched off) the magnetic field collapses, this generates a voltage in the secondary windings. This generated or induced voltage is dependent upon the ratio of the windings (primary to secondary), the design of the coil and how quickly the voltage is turned on and off.
The switch that was used for many years was the ignition contacts. These were mechanically driven by the engine and timed to trigger the ignition just before the piston reached top dead centre. During the late 70’s and early 80’s electronic ignition replaced the mechanically operated contacts. This enabled a faster switching speed (hence higher voltage output) and more accurate ignition timing settings (no mechanical switch to wear/deteriorate). Electronic ignition used a non-contact sensor (hall or inductive type) that was the forerunner to today’s cam/crank sensors.
With government legislation dictating the need for ever decreasing mixture strengths and engine manufacturers designing more and more powerful engines, the need arose for higher voltage ignition systems. High in-cylinder pressures, hot combustion chamber temperatures and lean mixture strengths all make it difficult for the spark to jump across the plug gap, thus a higher voltage spark is required. The most demanding applications include turbo/super-charged, lean burn or direct petrol injection applications. Following the advent of electronic ignition, designers turned to developing the ignition coil.
At this point, the traditional ignition system had reached its limit. It became “saturated” at the higher voltages demanded and alternatives were sought. The higher voltages required to trigger the spark also caused under bonnet problems with high tension (HT) lead insulation, both voltage and emission interference. A new design ignition system was called for, leading to the development of resin filled plastic coils, and the reducing popularity of distributors and HT leads.
The development of these coil “packs” has only been made possible with the advent of computer aided design packages (CAD). The coils are designed and tested before manufacture. The coil assembly is now precisely matched to the other ignition system components (plugs, ECU driver stage etc) all of which are integral to the engine management system.
The secondary circuit of the coil is now completely isolated from the primary (see diagram below), this allows the use of “double ended” coils with two HT outputs, these are also incorporated into multi cylinder “packs” comprising of an assembly of double ended coils to enable “coil per cylinder” set ups. Also, as resin coils can be made smaller and of any shape they can even be fitted directly on top of the spark plugs (pencil coils).
Coil on plug units reduce the electrical capacitance of the HT circuit and reduce the number of HT components by removing the “weak link” – the HT lead. This also increases ignition system reliability.
3.In order 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 as 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]. It is important to note that if the fuse is intended to be used in an environment with possibly very high or low ambient temperatures, then the nominal fuse current would need to be sized significantly higher or lower (see ambient temperature below).
4.given data:
P=500W , V =12v,find capacity of battery.
Solution:
I=p/v= 500/12 ,
I= 41.67 Amps
current (Amps)convert into current per hours(amp-hr) Q=I*t
consider timing (t = 1hour)
Q (Ah) = 42*1
Q= 42 Ah
:. capacity of battery (E)= charge capacity(Q) * voltage(V)
E=42*12
E= 504Wh
:. I recommend to a battery capacity above 500 Wh.
5).batterey to lights ,beam and horn are connected parallel to each other. f two or more components are connected in parallel, they have the same difference of potential (voltage) across their ends. The potential differences across the components are the same in magnitude, and they also have identical polarities. The same voltage is applied to all circuit components connected in parallel.
6).battery to fuses, starter, ammeter connected in series are connected along a single "electrical path", and each component has the same current through it, equal to the current through the network. The voltage across the network is equal to the sum of the voltages across each component.