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Recombination or tall tubular Batteries

Recombination or tall tubular battery is the recent development in the lead acid batteries. These batteries are also called gel cell batteries due to their construction. Recombination batteries or jell cell batteries don’t use liquid electrolyte. But they use special kind of separators which holds electrolyte gel in them. This gel type material is a cream type acid electrolyte. These separators are places between the plates and they make good and low resistance contact with plate grids. They have a spiral construction like a capacitor.

Tall tubular battery

 The spiral design provides more plate area compared to the conventional straight plate type plates. Also the close plates design provides less resistance. Due to this design the output voltage and current have greater value than the conventional lead acid batteries. These higher voltages usually 0.6V provides more power in cold cranking and starting. In these kind of batteries the gas formation is virtually zero and battery can be charged faster than usual.

The recombination batteries have more safety features and advantages. Following are few:

1.       These batteries can more provide much more cold cranking current. The cold cranking current could reach up to 900 amperes.

2.       The combination or tall tubular batteries can withstand real deep cycling and they would not be damaged.

3.       Combination or tubular batteries life expectancy is more. They can last four time more than conventional lead acid batteries.

4.       Combination or tall tubular batteries could be installed in any direction as there is no liquid electrolyte in it so they don’t need any specific direction for installation.

5.       Combination or tall tubular batteries have no liquid electrolyte so they don’t spill even if the case of the battery is cracked.

6.       These batteries and their terminals are corrosion free.

These batteries has very low maintenance as there is no electrolyte or water loss in them.

Hybrid Batteries

Hybrid batteries are type of battery which combines the advantages of both maintenance free and low maintenance battery. Hybrid battery can withstand seven deep cycles without losing its charge retaining capability. The grid construction of hybrid battery is special and it contains somewhat 2.76% antimony as alloy in the positive plate and calcium as alloy in the negative plate. Such formulation of the battery plate allow it to withstand the deep cycle performance and also it provides better performance on cranking. The use of antimony in positive plate as alloy reduces grid growth due to which the plates shorting together and corrosion also. Another material lead calcium in positive plates producing less gasses than conventional batteries are producing.

Hybrid battery pack

There is another difference of these batteries manufacturing that their plates have lug which are located very close to the center of the grids. Another difference is the horizontal and vertical grid bars are arranged in radial shape. These two arrangements the center lug location and the radial grid bars design makes the plates less resistive and provides shorter path to the current produced by the battery. This makes the battery producing and delivering more current at faster rate.

In this kind of batteries glass separators are used which are coated with resin. Glass separators have low electrical resistance and high chemical contamination and less reaction with chemical. They have prolongs life and strength. Such a construction of the battery provides more battery life and much better cranking performance.

Some people confuse hybrid batteries with batteries used in hybrid vehicles. This point must be cleared that hybrid battery in this article don’t mean the battery that is used in hybrid vehicle instead this is a type of battery which is the improved form of sealed lead acid maintenance free battery and the low maintenance batteries.

Hybrid battery cell

Although hybrid vehicles do used such kind of batteries as their battery bank but that is not a must. Now a days an new kind of battery have been invented by two scientists which have a very prolonged life or about 20 years with very good charge capacity to weight ratio. These batteries have charge discharge cycling expectancy of 10,000. These two scientists have been awarded with Nobel Prize for their invention.

Maintenance-Free Batteries

Maintenance free battery is same like a regular lead acid battery. The chemistry of the battery is little bit change for sealed battery. The other difference is such kind of battery is sealed and there is no provision of addition of water in cells in sealed batteries. This kind of battery plates material is little different than the regular or conventional lead acid battery. This type battery plate grid contains calcium, strontium and cadmium to reduce gas formation during charging. In conventional lead acid batteries water electrolysis takes place and water molecules are broken down into Oxygen and Hydrogen molecules and the Hydrogen gas escape out from the battery vents. Whereas in the sealed lead acid battery the addition of the extra materials mentioned above reduces this gas formation during charging.

Sometimes additional support is provided to the plates which increases the conductivity of the plate to its connecting tab. The plates are wrapped on an envelope shape separator which covers the plate perfectly from all three sides. The separator is made of porous material and it gives path to the electrolyte but is seals the active materials effectively not to escape them from the battery plates. These batteries are sealed but small vent is provided on the top to the valve regulated chamber where water vapors are accumulated and regulated back to cells. This way water and gases cannot escape from the battery so there is no need to add additional water or distilled water periodically to maintain the electrolyte level like in conventional lead acid battery.

Maintenance free battery

Some maintenance free batteries have a built in hydrometer on the top of the battery case. That indicates the state of the charge of the battery. A hydrometer is an instrument which shows the specific gravity of the electrolyte in the battery. The specific gravity of the battery is directly proportional to the charge of the battery. The hydrometer on such batteries when they are charged more than 64% shows green indication. The black indication on the hydrometer shows partial charged battery less than 64% charges. Whereas a silver indication indicates that the battery electrolyte is completely used and become water and there is a need of battery replacement. This indication is an easy way for a driver to understand the battery condition and replacement interval.

Several battery manufacturers have changed the maintenance free batteries to another type low maintenance battery. For those batteries caps are removable for testing the electrolyte and to emulate the level of electrolyte.

There are a few advantages of sealed lead acid batteries:

1.       They have longer shelf life. Approximately 2 years.

2.       They have larger quantity of electrolyte in the battery compare to conventional batteries.

3.       These batteries are shipped with electrolyte in them and ready to use. There is no more need for bothering electrolyte refilling and charging when shipped.

4.       They have ability to provide more current even if the batteries are cold. They have higher cold cranking amperage.

5.       They have more resistance to overcharging. They withstand overcharging better than conventional batteries.

There are certain disadvantages also of the maintenance free batteries. These are:

1.       They have faster discharge rate on parasitic loads.

2.       They have low reserve capacity.

3.       They have a shorter life span. Their life is shorter than conventional lead acid batteries.

4.       They are not good on deep cycling.

These batteries are not suitable for high temperature exposure. At high temperature they become faulty due to grid growth.

How lead acid battery works

Lead batteries when they are shipped, they are dry. No electrolyte in them. Instead electrolyte is supplied in plastic containers separate with batteries. When battery is needed to be installed in the place where they are needed, electrolyte is filled in it. Most batteries are dry charged and they are ready to use when electrolyte is filled in. But a slow starting charge is always recommended. The electrolyte starts chemical reaction in the battery. The reaction is done between the positive plate lead peroxide and the negative spongy lead. The electrolyte works as ion carriers. It reacts with plates to produce electricity and also it carries ions produced.

The fully charged automotive battery has specific gravity 1.266 at 81 degree F or 28 degree Celsius. The plane or distilled water specific gravity is considered to be 1. So the battery electrolyte is 1.266 times heavier than water. When battery is used, the specific gravity for it reduces as the acid in the water reacts with plate material. This way specific gravity is a measure of battery charging state. Following detail shows how battery charge relates to the battery specific gravity.

Fully charged Battery: 1.266

75% charged Battery: 1.226

50% charged Battery: 1.191

25% charged Battery: 1.156

Discharged Battery: 1.121 and lower

Specific gravity figures could vary little with design and manufacturing parameters of battery. But one thing is common regardless of battery manufacturer and design, the battery electrolyte specific gravity reduces with battery discharging. Temperature also effects the specific gravity of electrolyte. When the temperature increased beyond the standard temp rapture 81 degree F, the specific gravity of electrolyte decreases and when the temperature reduces the stated limit, the specific gravity of the electrolyte increases. The electrolyte specific gravity is temperature sensitive and the reading drastically changed with the change in temperature. A general rule of thumb is to minus 0.004 to specific gravity reading at each 10 degree F increase beyond 81 degree F or 5.5 degree C above 28 degree Celsius and add below this temperature limit.

During the operation of a lead acid battery the battery is never discharged completely instead partially discharged and then charged again to compensate for the discharge. This cycle is repeated for the entire life of the battery. During this charging and discharging cycles the battery plates active materials reacts with the acid and slowly wears away from the cell plates. This sulfates the battery plates. Also the active materials are removed from the plate and accumulated in the bottom of the battery. These materials are conductive to electricity. Sometimes these accumulated materials shorting the positive and negative plates in battery cells. And also when the materials removed from the cell plates they become basic lead grid plates which are no longer able to produce electricity. In such a condition the battery must be replaced with a new one. The older battery should be sent to manufacturer for recycling. Some people try to repair these worn out batteries by putting different items like Epsom salt or Coca Cola. Such techniques don’t work and this is just waste of time and resource.

Lead acid battery construction

Lead acid battery construction consists of the following elements or components

1.       Battery case

2.       Battery terminals

3.       Negative plates

4.       Positive plates

5.       Insulators or separators

6.       Battery posts or terminals

7.       Electrolyte H2SO4

There are two categories of commercial batteries. Three year and Five year. The main difference between them is the materials used in their manufacturing. The material means the active material used to construct battery plate. These materials are reacting with electrolyte and produce electricity. Both positive and negative plates have different active materials. The quality and price varies for such materials. Also the manufacturing quality varies. Cheap plates are manufactures with ordinary process by common people whereas good quality plates are made by high pressure hydraulic machines with specialized procedure by specialists. Both low quality and high quality plates have different life span and different performance and efficiency.

Lead acid battery construction

Plate is basically grid plate like thick mesh made of lead alloy. In the plate lead material 6 to 7% antimony is mixes to provide good strength to grid. Plates have tabs attached to them so that tabs can be welded latter with connection terminals. The plate has vertical and horizontal grid bars which intersect each other at right angle.

The active material is powder lead oxide, material expander and acid H2SO4. This material is made like a thick past and pressed with pressure in plate grids. After drying a forming charge is provided to the plates. The forming charge makes the plate polarity negative or positive.

The forming charge is provided in the battery electrolyte same like charging a battery. When providing forming charge the positive plate active material is converted into lead peroxide. The negative plate active material is converted into spongy lead.

The positive and negative plates are fixed alternately and welded each type of plates together on one side. This arrangement is known as a cell. Usually 7 to 13 plates of each polarity are connected together to make a cell. Both plates are insulated or isolates by special type of insulators known as plate separators. These separators are special insulating material which is micro porous material. These insulators are separators hold and pass battery electrolyte. These separators are effectively providing battery electrolyte to the battery plates during battery function as they are locates close enough to the plates.

The cell is completed by welding all positive plates together on one side and all negative plates on the other side. They don’t touch to each others at any point. If the touch to each other, a short circuit could create and the cell will be referred as a shorted cell. Six cells are normally connected in series to make a 12v automotive battery. Each cell has 2.1v level and current depend upon the area and number of plates. So all cells in series make a voltage level of 12.6v.

Battery case is made of ebonite, polypropylene, plastic or any other hard rubber materials. Battery case should be able to withstand mechanical stress and vibration in the vehicle during its running. Also the battery case should be inert with battery electrolyte and should not react with electrolyte. Battery case is separating and isolating each cell from the adjacent cell electrically and physically. It should provide air tight sealing between the cells. Battery lids are provided on the top of the battery case. These lids are threaded on the battery top. They are to be filled electrolyte once and to be filled distilled water and maintain the electrolyte periodically. These lids have vents in them. These vents are discharging gases produces inside the battery during charging process and discharging process. These vents should be kept cleaned so that they pass the gasses without any hurdle.

On the top of batter or sometimes on the sides two terminals positive and negative are provided. These terminals are used take power form the battery and provides power to the battery during charging. They are sometimes referred as battery posts. These terminals or posts are round shape lead posts which are making connections to the vehicle electrical system. They are round shape posts.

Battery electrolyte is 63% water and 37% sulfuric acid by weight. Electrolyte reacts with plates active material and produces DC power with is supplies by battery. With the use and passage of time electrolyte level depletes and reduced down. To maintain level, distilled water is added from outside. Never add acid but add only distilled water to maintain the level. Also plan drinking water should not be added as that contains minerals and salts which are harmful for battery.

Batteries when becomes older and they loose efficiency, they should be sent to manufacturer for recycling. Some people are trying to repair them by adding different chemicals and substances like Epsom salt and Coca Cola. Such actions are useless and they have no benefit. As when the battery become aged, the active material is removed from the plates and all active material is consumed so that battery will be no more serviceable and could not be made serviceable by such useless actions.

The need of battery in a vehicle

When vehicle or car engine is at rest and in stop condition, the only power source you have to crank the engine initially from standstill is the vehicle battery. At starting the self-starter motor draws several hundred ampere of current from the battery. The current draw depends upon the engine condition, size of the engine and temperature of the engine. The new and high compression engine needs more power to crank it hence more amperes the self-starter will draw. An old and worn out engine have less compression so the self-starter needs less current to crank it. Size of the engine also matters. A big size engine needs more amperes on the self-starter to crank it. Same is true for a diesel engine. As diesel engine have bigger size, much more compression and more accessories attached to it compared to a gasoline or petrol engine of the same capacity and capability. The temperature of the engine is another parameter in self-starter current draw. In cold weather the oil in the engine becomes more viscous and it offers more friction to rotation. So it is difficult for a self-starter motor to rotate a cold engine compared to a hot engine.

When vehicle or car engine starts, its alternator spins with engine and produces electricity to charge the battery and also it powers up all the accessories and systems on a vehicle or car. Normally alternators on a vehicle produce current from 50 to 160 amperes which is considered to be sufficient for almost all needs and requirements on a vehicle. But sometimes needs arrive when some heavy load needs to be operated on a vehicle and demands arise when huge amperes are required to fulfill that requirement. In this condition the vehicle battery supplied the extra amperes to meet the requirement. This is especially is the case when vehicle is idling and all the accessories are switched on.

There is another requirement on the modern cars when the key is at off position and engine is stopped, even the systems on the vehicle consume little current to keep the systems up. These include immobilizer, auto doors, proximity entrance, body computer, engine ecu, clock, stereo and cameras. These systems take little power to do some special functions and keep their memory. Usually they need as little as 40 miliamperes to keep such systems alive. But this small current draw also drains the battery in a week or more if the vehicle is not started periodically to charge the battery. So this is important to start the vehicle after certain time period to keep it in good running and starting condition. Another advice could be to loose one of the battery terminal if you are about to park the vehicle for long period of time. Another possibility could be the use of an external charger on the battery to keep the battery in charged state all the time you keep the car parked.

In case if the chagrining system of a vehicle fails, all the accessories and car engine current and electrical power requirements will be fulfilled by the battery and battery will provide power to all circuits including fuel pump, ignition system, fuel injection and some other circuits. In this situation the battery will power up everything up to certain level till the battery terminal voltage reduce down to a specified level at which the battery would be empty. This time is about two hours for most batteries supplying 25 ampere of regular current.

Battery power depends upon a few parameters. Those include plate size, no of plates, battery weight, plate material and quantity of electrolyte in a battery. These all parameters are dependent to each other. It is not possible to increase one parameter to get more power. Instead all parameters are battery design parameters and they are well calculated during battery manufacturing.

Automotive Batteries

Introduction

Car battery in electro chemical device which have capability to store and reproduce electrical energy. Car battery is storing electricity in the form of chemical energy. Electro chemical is a reaction which takes place when two dissimilar material plates are placed in electrolyte then electric current flows in the result between the two electrodes. The two dissimilar plates are made of lead. These plates have mesh like structure. These plates hold two different active materials in their mesh type structure. When such plates are immersed in acidic electrolyte, electricity is produced. Batteries produces DC or direct current. The DC current has property that is flows in one direction and it don’t change its direction and quantity with time.

There are two operation performed in a lead acid battery. Those are charging and discharging. When battery is charging, Current is flowing from the charger into the battery and battery stores this power in the form of chemical energy. Next when discharging, the battery chemical reacts and it produces electricity and current flows from the battery to the load. When the battery discharges the plate material reacts with electrolyte acid and changes its chemical state. This change of state can the reversed by charging the battery and by passing the current into the battery. So this action is repeated hundreds time during the battery service life. Eventually time comes when plates are destroyed permanently and the battery no more deliver the current or store the energy. At this point the battery becomes unserviceable and needs replacement. The old batteries are sent back to manufacturer for recycling.

Automotive or car battery has crucial role and function in vehicle. Such functions are as under:

The battery provides electricity to all vehicle accessories when engine is stopped and when the charging system don’t charge the battery.

When the vehicle is started and running, it store the energy and give it back when the vehicle engine is stopped.

It helps to provide power to the vehicle when extra power demand comes and alternator could not fulfill the needs.

The battery works like a stabilizer to regulate the voltage for all the automotive electrical system.

The battery starts the vehicle engine from stand still. When first time starting the engine from stop, the battery provides substantial amount of current to the self-starter which is a dc motor and its cranks the engine. The same time it provides the electrical power to the rest of the vehicle electrical systems to make the car started.

Electrical Short Answers Questions for job interview

1. Define how we can find the wire size by knowing the American wire gauge AWG and matric methods.

Answer: There are two standards for wire gauge. American Wire Gauge AWG and Standard Wire Gauge SWG or matric. These standards define wires according to their diameter. They give numbers to different diameter of wires. The bigger the number, the lesser the diameter of wire. For example wire gauge 12 wire would be thicker than wire gauge no.22.

1.       What is component locator and why it is used.

Answer: Component locator is information detail for a certain system and it shows the physical location of the different components used in that system.

2.       Define how the wire resistance is affected by temperature.

Answer: with the increase in temperature the resistance of a wire also increased. This is known as positive temperature coefficient. Some materials resistance decreases with the increase in temperature.

3.       Describe the three factors affecting the wire size.

Answer: they are a. length of the wire. B. vibration the wire will be exposed to. C. the temperature of wire.

4.       Why printed circuit boards are used.

Answer: printed circuit board give ease of circuit design. It simplify the circuit wiring. With the printed circuit board mass production is easy.

5.       Describe the use of single strand wire and mutlistanded wire.

Answer: Single strand wire is used where is less current flow and the wire is not subjected to substantial vibration. Whereas the mulistanded wire is used where there is a huge current flow through wire and flexibility is required and where there is vibration.

6.       Why circuit diagrams are used.

Answer: circuit diagrams are very useful and powerful tools for service engineer and for service technician as they provide help locating wiring interconnections between components and also they provides details of powers and grounds.

7.       What is simple and complex wiring harness

Answer: Simple wiring harness serves single or less circuits. Complex wire harness serves for several circuits.

TL494 Pulse width modulation pwm smps controller

TL494 pulse width modulation pwm smps controller is a very famous IC which is very commonly used as atx pc power supply smps controller. Their use is not limited to atx power supplies but they are also used in inverters and dc to dc converter. This device has all the necessary circuitry built on a chip which provides a very flexible and reliable switching regulator performance. TL494 chip or ic has two error amplifiers in it. There is an adjustable frequency oscillator on the chip. There is dead time control DCT which is a comparator. There is pulse steering control flip flop. There is internal 5V reference regulator and output control circuit used to interface with the outside world.

TL494 pulse width modulation smps controller

TL494 has two error amplifiers which works on common mode voltage whose range from -0.31V to Vcc-2.1V. Dead time control provides a 5% dead time and the dead time control comparator dtc has fix offset. The chip internal oscillation can be used or can be bypassed. It can be bypasses by terminating RT to reference output. This pin can be provided saw tooth input to CT. It can command common circuit in synchronous multiple rail power supply fashion.

TL494 chip or ic has two transistors output. These two transistors can be connected as common emitter or in the other way it can be configured as emitter follower. TL494 output can be selected as push pull or single ended. Both operations can be selected by output control function. The architecture of the chip is so good that it don’t allow mistake in the output.

TL494 IC images

There are two variants of TL494 available most commonly. The TL494C chip has operation temperature of 0 degree Celsius to 70 degree Celsius. Whereas TL494I chip can operates on extreme temperature of -40 degree Celsius to 85 degree Celsius.

TL494 chip have following features

1.       This chip internal circuit prohibits the double             pulse at the same time at either output

2.       TL494 output can be selected as single ended           or push pull

3.       TL494 chip is a complete switching regulator and consist all necessary circuits for power supply.

TL494 outputs high current pulse of 201mA as source or sink.

Electrical wiring wire types

For automobile electrical wiring wires and cables are made of strained copper wires and for insulation polyvinyl chloride or PVC is used. Strand wire has quality of flexibility and better current flow performance due to more surface area and skin effects and less resistance compared to solid wires.

To determine the exact size or diameter of wire three factors are considered. 1. Wire or cable used in automotive wiring should withstand certain level of vibration as vehicle is vibrating all the time during running. 2. Wire should bear certain degree of temperature or heat as it will be exposed to heat in automotive during its service life as the engine is producing certain amount of heat when it is running. 3. Wire must have enough diameters so that it could carry certain amount of current without substantial voltage drop. This is especially critical for light wiring.

Electrical cables and wires size is the diameter of the conductor used in the wire or cable. Four factors affect the resistance of wire are conductor diameter, wire temperature, diameter and wire conductor material.

Breaded ground straps are provided to make a complete return path from component to battery negative. They are helpful for insulating parts grounding and they reduce electromagnetic induction EMI also.

PCB or printed circuit board are used everywhere in electrical and electronics. They are used in vehicle computers, instrument cluster and many other places. PCB makes the mass production of electronics very easy and affordable. PCB uses glass fiber sheet or some other insulated fiber sheet to support component and copper traces are provided on the board to make interconnections between devices on pcb.

Wires are grouped and bundles and made a wiring harness. Wire harness provides mechanical strength and neatness to the system. At the end of wires connectors are provided to interconnect the wires.

Wiring diagram and electrical schematics are very helpful for technicians and engineers. They provide benefit to identify the components interconnections and components location. Drawings also provide power and ground locations in a vehicle.

Wire color coding is used to identify wires. Sometimes two colors are used on a wire. The second color strap is called tracer. This provides more flexibility to color coding. Sometimes numbering system is also used to identify the wiring wires.

Circuit diagrams use symbols to show different electrical components in a vehicle. They don’t show the actual shape of the component. Knowledge of symbols could help to troubleshoot faults according to the circuit diagram.

Terminals and lugs are crimped and soldered to the wires conductors. Terminals are used to make electrical connection between components. They should be able to withstand heat and vibration.

In electrical system wire harnesses are used to group or bundle wires. They branch out wires to interconnect with components. Harnesses are helping to reduce hanging and loose wires under the hood and under the dash board. Harnesses provide safety path to lights and sensors connection.

Electrical Circuit Numbering and Color Codes

Cables and wire used in electrical wires have colored insulation on them. Cables and wires are covered with different color insulation. Even two colors are used on one wire to make more color selection. The color on wire insulation have its specific purpose. The wire color coding represents different wires and different circuits. Sometimes numbers and symbols are included in schematic diagrams. These codes and numbers help technicians and engineers working on the specific systems.

Wiring colors are standard for all manufacturers. They use different color schemes according to their own need. But they specify their color scheme in service manuals and other service material. This is a good idea to learn the manufacturer wiring color standard and coding before working on a specific system.

In electrical wiring the first color group letters shows the base color of wire and the second letters are showing the color of the strip or tracer on the wire. We can say for example we have a wire for which the diagram shows the letters BLK/RED. This shows black base color for wire with a red color strip on it or red color tracer on it. Tracer is a line or a dashed line on the wire whose color is setup different than the base color of the cable insulation. This is made to make more selection in case of complex wiring in a system.

Cars manufacturer Ford use four coding methods for color coding their wires in their cars:

a.       Solid or one color

b.      Base insulation color with a stripe or tracer on            the base color

c.       Base insulation color with dash line or hash              marks

d.      Base insulation color with dots on the base color

The other car manufacturer Chrysler adapted the numbering scheme to show the circuits on the wiring diagram. This numbering scheme includes circuit identification, wire gauge and color of wire. All these information are included in the number used by Chrysler.

Generl Motor uses even more detailed and complex coding number scheme in their cars. Their identification code includes wire color, wire gauge in millimeters matric, the circuit number and the ground identification.

Electrical Wiring Schematic Diagrams

Wiring diagrams and schematics are very important for electrical system repair and maintenance. Electrical wiring diagrams and schematics are showing the actual electrical devices and items connections and cabling through symbols. For any electrical system the wiring diagram have great importance. Electrical diagrams and schematics shows the circuit interconnections, devices locations, power and ground locations and different connectors details and locations and pin designations. These diagrams are showing interconnection of different circuits also. They show details of powers and ground connections. In a vehicle on kind of power is not used. There are controlled and uncontrolled power connections are provided from battery. Drawings show the wire color codes also. Different function wire use different wire colors. Such color coding is mentioned there by colors or by writing. All this information is very important for service technician and service engineer.

Sometimes electrical wiring diagram explains special information on some part or circuit. Every time electrical circuit diagram doesn’t explain the function and working principle of a circuit. In this case technician and engineer knowledge and understanding come true. Without electricity understanding and knowledge of circuits, one cannot troubleshoot and repair with the help of electrical circuit schematics.

There are two types of circuit diagram in common use. One is the detailed wiring diagram and the other is the block diagram. The detailed wiring diagram is showing all details of wiring from point to point. The other type is block diagram. The block diagram shows one line detail of the system. Block diagrams are important to understand the boundaries and scope of the circuit and functionality of the circuit.

Electrical circuit diagrams and schematics are long enough that the entire circuit diagram cannot be covered on a single page. So the circuit diagram and schematics are split in systems and circuit. So each system and circuit is explained on one page. Even one circuit could be explained on several pages. There are references given on each page to give easy understanding of interconnections of wires on different pages.

In electrical circuit diagram and schematics wires are crossing to each other. Sometimes a semi-circle type shape is used to show insulated crossing of wires. In other diagrams and schematics don’t show the semi-circle shape instead they just cross each other. A bold dot is used where there is connection between wires. This practice used in complex and more populated circuit diagrams.

Wiring diagrams are usually showing the interconnection of systems. They don’t show the internal circuitry of modules and computers. Modules and computer diagrams are manufacturers confidential secrete which they don’t share normally. Sometimes engineers and technicians make their diagrams and internal details.

Electrical Switches

In electrical circuit switch is one of the most common controlling device which controls the flow of current to accessories and electrical circuits. The switch provides on and off control to various electrical circuits and systems. Contacts are used to carry current inside switch when switch is in on or closed position. When the switch is opened or in off position the flow of current is stopped.

Electrical switches

There are two main kinds of switches. Normally open and normally closed. Normally open switch don’t provide the current path when it is at rest or in off position. It only provides path to current flow when it is in on or closes position. The switch contact remains opened when it is at rest position until an external force doesn’t actuate the switch from off to on position. In this way the circuit is completed and current flow starts.

The other type normally closed or NC switch allows current flow when they are in rest or at off position. There contacts remains closed when they are at rest position. When an external force actuates such kind of switch, its contact become opened and stops current flow or cut off current path from the certain circuit. This way such kind of switch only pass current when it is in the rest position.

Another classification of the switches are according to its make or functionality. Single pole single throw or SPST is the simplest switch used to control simple circuits. There is a single pole which can pass to a single position only when it is actuated. Such type of switch only controls on and off operation of a single circuit. There is another type of SPST switch which is spring loaded type. Such a switch is known as push button. In this kind of switch the contacts are hold by a spring and closing the contacts when it is momentarily pressed. When press is released, the switch comes back to rest position due to the loaded spring. This type of switch is used to control horn and circuits where momentary position is translated to the computer system.

Electrical Wiring Harness

Wire harness is used to bundle wires in electrical systems. Wiring harness is combining wiring wires so that they don’t become loose and wiggle here and there. If wiring harness is not used the wiring wires would hang under the hood and dash board in a vehicle which could be very ugly and dangerous also. Wiring harness safely lay wiring to different part of vehicle like lighting system, engine, accessories and other parts of the vehicle. Wiring harness is made by combining wires together and wrap them in some sort of insulating tape. Inside the harness wires are bundled in groups and joined them with the help of connectors. Multiple pin connectors are used which have plenty of pins like 80 pins per connector.

Wiring harness for car

Wiring harnesses are complex as well as simple in a vehicle system. Usually engine compartment and under the dash board complex harnesses are used. Lighting and some sensors are using simple harnesses. Simple harnesses serve only few circuits and simple applications. Whereas the complex harnesses serves complex harnesses and applications. Sometimes some branch harnesses are separated from the complex harnesses for some specific areas where some parts are installed and they are part of the complex harness. Such case you can observe in the engine compartment where sensor harnesses are joining the main harness.

Wiring harness connection

Mostly insulating tape, cotton or harness plastic flexible tube is used to make wire harness or to protect wiring harness from outside. Some wiring harness have seam in them from where you can open it whenever repair is needed or new wiring addition is required. This seam remains close all the way the harness length and also it remains closed even on bends. Sometimes people do use PVC insulation tape to make wiring harness. Such tape harness works but in the oily environment and in temperature environment it don’t work and it starts unwrapping. Harness tube is a better choice in such a case. They are available in different sizes and diameters.

Printed circuit board PCB

Printed circuit board was first developed and invented by British scientist J. A. Sargrove in 1947. Such circuit boards were used by that time in the production of Radio receivers. Latter they became part of everything! Today printed circuit boards are present everywhere. They are essential part of any electronic equipment.

Printed circuit board provides base plate to mount electronic components on and simplify the electrical connections between components effectively. Printed circuits boards are used in computers, clocks, radios, tv, plc, industrial control systems, stereos, cellphones, mobile phones, meter clusters, vfd, soft starter everywhere. Their uses are unlimited and undefined today. An estimate had been made which says till the date circuit boards are manufactured somewhat equal to the size of the earth!

Printed circuit board is made of insulating material plate like fiber glass or acrylic sheet and copper sheet is pasted on the top of it. Then circuit is drawn over the circuit board and wiring is made through etching process. Components are soldered to printed circuit board either on copper side or on the other side through holes. In older days through hole technology was used whereas today surface mount technology is used to solder the components directly on the copper side of the printed circuit board.

Connectors and wires are solders to printed circuit board to make connections to the printed circuit board to outside world. Printed circuit boards provides reliable and effective mean of connections through copper tracks. Printed circuit boards can withstand vibration to some degree. Printed circuit board is the most effective way of mass production electronic items as gadgets. Before printed circuit board mass production was not that easy.

Printed circuit boards can be single layer or multi layers. Multilayer printed circuit boards are used to make complex circuit where a lot of wiring is involved. Single layer printed circuit boards are simple and they are easy to work on them. Mostly single layer printed circuit boards are used where space is not a problem. Also they are used for power electronics as power electronics produces significant heat which is not suitable for multilayer printed circuit boards.

Electrical Connectors and Terminals

Wiring is used to connect different components to the power and ground source in the vehicle. In between the wiring terminal connectors are used to effectively connect and disconnect the wiring when there is a need of disconnection. Modern vehicles use more than 500 connectors for different components and circuit connection.

The terminal connections should make such connections with very low resistance and ensure minimum voltage drop on such connections. Terminal connectors are made of brass, copper or steel. They are tined, leaded or sometimes silver plated. Such plating prevents corrosion. Corrosion can cause loose connection and loose connection results in voltage drop. Voltage drop is an unwanted thing. Voltage should only be dropped on engineered circuit load. Voltage drop on cable connections and other places reduce the circuit efficiency and reliability. If had been observed if a connector used in the lighting circuit in a vehicle reduces 1.3V could reduce 33% light efficiency. To avoid this reduction in functionality all connectors and switched in the system should be of premium quality and good conductivity.

Terminals are normally crimped using a crimping tool or soldered using soldering iron to the wire conductors. As terminal connectors are making connection in wiring, they should be capable of bearing vibration as in vehicle they could be subjected to vibration during vehicle running.

Terminal connectors have different types. Their name employee their shape and function. Following are a few types of terminal connectors.

Molded connector

Such connectors normally have 1 to 4 wires which are molded in one piece component. Such connectors halves could be separated but connector cannot be separated itself.

Multiple wire hard shell connector

As the name shows such connectors have hard plastic shell which holds the connecting terminal. Wires terminals can be separated from the shell for repair.

Bulkhead connectors

Such connectors are used when many wires or cables are passed though bulkhead.

Weather pack connectors

Such connectors have rubber sealing on them to prevent terminals from moisture and water entrance. These connectors are weather safe as they don’t corrode in wet moist weather. They are normally used on computer circuits on the vehicles.

Metri pack connectors

Such connectors are like weather pack connectors but they don’t have rubber seal on them.

Heat shrink covered butt connector

Such connectors are specially used on air bag circuit applications. They have special use and sensitive use.

Splice are used to reduce connections. Splice can be used on power and ground. They are most commonly used on ground circuit. They are very useful if there are several components and devices located close to each other and they commonly use power and ground connections. In such a case those all powers and grounds are combined to a single splice and that splice is connected to the power or ground through a connector. This effectively reduces wiring and connectors.

Electrical wiring system

Introduction

Modern vehicles have very long and complex electrical wiring system in them. If all the wiring length could be measured, it would be a mile or so. Modern cars technicians must have good knowledge of electricity and reading electrical schematic diagrams and circuit diagram is essential skill for them. To cope with electrical problems good knowledge of drawing reading and testing is a must. Without understanding electrical system and wiring of a car, repairing a car could be very much difficult and would become a nightmare. Understanding different symbols used on electrical schematic diagrams would help a lot a technician working on automotive systems. A technician must be aware of the current flow through the system and he must be aware of using appropriate size and gauge of wire to be used in a specific location and circuit to ensure proper current flow without heating up the wire due to excessive current flow. A technician can cause very easily a serious problem to the automotive system by using wrong size and gauge of wire. The technician must be aware of the three factors influencing wire resistance. Those three factors are length of wire, diameter of wire and temperature of wire. Longer the length of wire, higher the resistance of the wire, thicker the diameter of the wire, lower the resistance of the wire. Higher the temperature of the wire, higher the resistance of the wire. With this consideration in mind a technician would not make a mistake and would be able to repair the car wiring system efficiently and effectively.

Automotive wiring types

There are two types of automotive wiring. Fist is primary wiring and second is secondary wiring. The primary wiring term is used for wiring in which wire carry current and low voltage is applied to them. There is 12v or 24v low voltage is normally used in automotive. So the part of wiring working on low voltage would be primary wiring. For primary wiring lower grade and thin insulation is used as low voltage don’t need much thicker insulation. The secondary wiring is that type of wiring which carries current and high voltage is applied to those wires. For example spark plug wires. For ignition system extra high voltage is applied of spark plugs. The wires carrying the ignition system current under high voltage have extra thick and special insulation to bear such high voltage.

Primary wire conductors are usually made of several strains of copper conductors twisted together. Several strains provide more conductor surface area and also makes the wire flexible. The insulation of the primary wires is normally thin as they face low voltage. The insulation is usually polyvinyl chloride or PVC. Some wires have another protective layer over the insulation.

Copper is commonly used because there is no other better substitute material compared to copper as it has lower specific resistance, flexibility, durability and easy availability. Other conductive materials like silver, gold, aluminum and tungsten are also used occasionally but they are not commonly used for making wires.

Wires used in automotive wiring are normally strand wires. Strand wires are those wires which are made of several strains of thin copper wires. These strains are twisted together to make a wire of them. Then these stains are insulated to make cables of them. Strand wires have less resistance than solid wires and they are very flexible. They offer less resistance because of skin effect. The electrons tend more to move on the surface than in the center of the wire. Strand wires have more surface area compared to the solid wire. This is because each strain in the wire has its own surface area which would become larger surface area compared to the same size solid conductor surface area. That is why the strand wire offers less resistance or impedance compared to the solid wire.

PVC insulation is used because it can withstand temperature extremes and it is inert with copper and don’t corrode copper. PVC insulation can bear acid, gasoline and anti-freeze. It is not reactive with such materials present in automotive and cars. The insulation has a very important purpose. It prevents the wire from shorting to ground as well as it prevents is from shorting to other circuits.

Wire Sizes

Selection of appropriate size wire for a certain circuit is very critical. The wire size selection is important to make the wire suitable for the current flow, durability, less voltage drop, less temperature emission and acceptable resistance. Following three considerations must be kept in mind when selecting wires for a specific circuit.

1.       Wire have enough thick diameter for the required length to carry certain amount of or current to the load without dropping voltage from the specified voltage drop limit to ensure proper operation of load.

2.       Wire used for a specific circuit should bear the amount of heat it is exposed to.

3.       Wire must be able to withstand certain value of vibration it will be expose to. Because in automotive vibration is a very common factor all parts expose to.

Wire size determines the amount of current flow through the wire. Larger diameter wire has less resistance and more current carrying capability. Lesser diameter wire has high resistance and have lower current carrying capability. There are two standards to measure the wire size. American wire gauge and standard wire gauge or matric. American wire gauge is AWG and standard wire gauge is SWG.

American wire gauge and standard wire gauge are designating numbers to different diameters of wires. The higher the number of AWG or SWG, the thinner the wire. The lesser the number, the thicker the wire. For example a 22AWG wire would be thinner than 12AWG wire.

Electrical terms defined

1.  Don’t fix a larger rated Fuse in a circuit which had been designed by the manufacturer.

 2. A switch can control the on and off operation of a circuit or direct the flow of current through different electric circuits.

 3. A normally open switch would not allow current flow when it is in its rest or in off position. A normally close switch would allow current flow when it is in its rest or in off position.

 4. An integrated circuit is a complex circuit made by transistors, resistors, diodes, capacitors, inductors and other electronic devices those are formed onto a small silicon wafer known as chip.

 5. When a positive voltage is applied to the N-material and negative voltage is applied to the P-material of a diode and, the diode is reverse biased. When a positive voltage is applied to the P-material and negative voltage is applied to the N-material of a diode, the diode is forward biased.

6. Transistor is used in electronic circuits as a very fast switching device.

 7. A diode is an electrical one-way check valve which would allow current flow in one direction and restrict the current flow in the reverse direction.

 8. Relay is an electromechanical device that uses low current to control a high current circuit.

 9. Potentiometer is a three wire variable resistor that functions like a voltage divider. Rheostat is a two terminal variable resistor that is used to regulate the strength of electrical current.

 10.  Thyristor or silicon controlled rectifier requires only a single triggering pulse applied to the gate to make it switch on.

A short circuit could result in a blown fuse.

A short circuit adds a parallel path to the original circuit, which decrease the entire circuit’s impedance.

A short circuit bypasses the circuit’s intended current path.

Circuit protection devices make the circuit open when short circuit occurs.

Electrical Short Answers to questions

1.       Define the uses of two types of semiconductor materials.

Answer: There are N and P type semiconductors. In N type semiconductor material the majority carriers are electrons and current passes through those electrons. In P type semiconductors holes are majority carriers and current passes through those holes. For forward bias the P type semiconductor is connected to positive voltage and N type semiconductor is connected to negative voltage to ensure current flow.

  2.  Which type of mechanical variable resistance is used on automobiles?

Answer: There are variable resistors used on automobile to translate the mechanical system position in terms of electrical signal or voltage level to system microcomputer. Those are throttle position sensor, accelerator paddle position sensor etc.

3.       Describe what is meaning of open, grounds, short, and high resistance.

Answer: There are three types of faults in electrical circuits which occur normally. These defects are open circuit, short circuit and high resistance fault.

4.       Explain the effect of each type of circuit defect that will have on the operation of the electrical system under defect.

Answer: In open circuit current can’t pass as there is break in the circuit so the circuit wouldn’t operate at all. In grounding a power wire or circuit touches to ground and it creates excessive current flow from power to ground. Short is condition in which electrical circuit or part of circuit makes connection or contact to another circuit or wire. In such a case malfunction of the circuit happens. High resistance is the state of electrical circuit in which un engineered resistance is created or produced naturally in the circuit. Such un engineered resistance is not defined and have no defined value. Due to this un engineered resistance excessive voltage drop produced and it limits the current in the actual circuit due to which the circuit don’t operate properly.

5.       Describe the use of a circuit protection device.

Answer: Circuit protection device like fuse and circuit breaker is used to protect the electrical system from excessive current flow. Also these protective devices are used to isolate the circuit from the remaining system if the circuit undergoes a short circuit.

6.       Define most common types of circuit protection devices.

Answer: There are two very common type of protective devices used in electrical system. Fuse and circuit breaker.

7.       Describe difference between a potentiometer and rheostat.

Answer: Potentiometer is a three terminal device and it is used as voltage divider to translate the mechanical position of a system to the system microcomputer. Rheostat is the type of variable resistance used to limit the system current.

8.       Define the difference between normally open NO and normally closed NC switches.

Answer: Normally open is a type of switch which has open contacts when the switch is at rest or at off position and it has closed contacts when it is activated or at on position. Whereas normally closed or NC is the type of switch which has closed contacts at rest or at off position. It has open contacts when activated or changed to on position.

9.       Describe differences between forward biasing and reverse biasing a semiconductor diode.

Answer: Forward biasing is sate of a diode in which the diode P terminal is connected to positive supply and N is connected to the negative of the supply. In such a circuit configuration the diode conducts and it passed current. The reverse bias is a state of diode circuit in which the diode P is connected to battery negative and N of the diode terminal is connected to the positive of the supply. In such a case the diode doesn’t conduct and wouldn’t pass the current.