Electronic Principles

[fiberglasscivic]

I thought we needed a thread that would give some basic knowledge for car electronics. Everyone seems to have problems with something electrical and this should help you troubleshoot those problems. I'll try to answer the most commonly asked questions and problems everyone sees along with give some basic electrical principles to help clear up things.



1. Basic +12 VDC Car Systems

Almost all cars on the road are based off of a 12V+ electrical system meaning that the positive terminal off the battery is used to separate pathways and regulate the system (via fuses, relays ...) Because of this the negative terminal will always be grounded straight to the chassis. This provides a great advantage to your electrical system by providing a direct connection to the negative terminal of the battery without the need to run a wire from the application to the battery. In basic 12V+ car electronics, this is referred to as "ground". This also provides a universal color code which most manufacturers’ use, red representing the positive connection and black representing the negative (ground). You will find that this is almost always true with any aftermarket products.

2. Some Basic Terms

Voltage - This is the measurement for the force that pushes the electrons through the system. You have two different types of voltage, AC and DC. AC is alternating current, thus named for the constant change in voltage which creates a wave. A normal house voltage is 120 VAC. This is made by a wave that changes from +60V to -60V. The difference is 120V. DC is direct current. It is named so because it doesn't change. On the positive side of a 12 VDC battery, you will always get +12 VDC (on a fully charged battery). It is a steady amount of voltage. The negative will always produce 0 VDC.

Current - This represents the amount of electrons pushed through the system. This is measured in amps (amperes)

Wattage - A measurement of the combination of Voltage and Current. Multiply your voltage by your amperage to determine wattage. For example, an amplifier that runs on a +12 VDC car electrical system and uses about 83 amps would produce about 1000 watts. This will vary depending on the actual output from the amplifier. The formula can be changed to help you determine different aspects of most applications.

Constant (Hot Wire) - A constant is a wire that provides +12 VDC when the ignition switch is completely off and the key is not in the ignition. The most common application for this is with a radio. The constant wire provides electricity so that when you turn off the car, you don't loose any preset stations or the time. This is also common with many other applications.

Circuit - A circuit is a combination of voltage and current that provides power to an application. There are 4 different types of circuits. The two primary ones are parallel and series explained later in Basic Electronic Principles. The other two are open loop and closed loop. An open loops circuit is when a circuit exists but is not in operation because a connection is not complete. A closed circuit is when a circuit exists and is in operation because the connection is complete. The easiest example of this would be the headlights on your car. When the switch is turned off, then the connection is broken and the circuit is not complete, but when the switch is on the circuit becomes connected and your headlights turn on.

Resistance (load) – This is somewhat self explanatory. Measured in ohms all electrical systems have some resistance somewhere.

Splice - To splice a wire is to cut the surrounding protectant away from the conductor and branch another wire from that location.

3. Basic Electronic Principles

All electrical systems require 3 things, voltage, current, and resistance (load). In a cars electrical system, fuses are rated to specific amperage because the voltage should never change (within a certain understood amount). The cars voltage should always read between 12 - 14 volts depending on whether the engine is running or not. Some vehicles may produce a slightly higher voltage (closer to 16 volts) depending on the user’s specific needs. Most +12 VDC car electrical systems use a parallel circuit to provide electricity to all the applications you use. There are two different types of circuits that could be used. You have parallel and series. In a parallel circuit, all of the positive wires are connected together and all of the negative wires are connected together. In a series circuit each application is connected in sequence. The positive wire from one application is connected to the negative wire of another application until the circuit is completed. In a parallel circuit voltage will remain the same while amperage will change. In a series circuit, amperage stays the same while voltage changes. A parallel circuit makes it easier for manufacturers to create applications and users to connect their application into the circuit. When you splice a wire to add a new set of gauges or new fog lights (or whatever your preference) you have just created a parallel circuit.

In any circuit you can only use the electricity that is available. If you are only provided 12 volts and 60 amps to work with, that's all you can use. This is one of the most common problems with aftermarket applications especially large stereo systems. Most cars electrical systems are built to use a majority of the amps provided by the alternator. When you start adding new applications to the existing ones, you may notice a change in the operation of the cars usual electrical operation. The most noticeable side effect is the dimming of lights. Dimming headlights are caused by two things. Either the alternator output for amperage is getting lower, or the applications drawing amperage from the alternator are drawing close to the maximum output of the alternator. If the output of the alternator is low, the only true fix to the solution is to replace the alternator. If the applications are drawing too much amperage there are a few different routes to fixing the problem based on your needs. You could either, change the alternator to a higher output, add a capacitor, add a battery, or remove the applications that are not needed for normal operation of the vehicle. Most likely you won’t want to remove the applications so we will only deal with the other options.

How to Decide
When making a decision on how to fix the problem, you need to consider what the application is that is causing the excess draw of electrons and how that application is affecting the rest of the electrical system. Changing the alternator to a higher output alternator is a good fix for small applications like neons or brighter headlights that don’t draw lots of current. A capacitor is a good fix for applications that require sudden, short, quick, and powerful draws of current. An extra battery or a better battery is best used for applications where there is a constant draw of excessive current. For example, if you have a subwoofer and amplifier that you only use occasionally, and you don’t have any other aftermarket applications, then you need something that can provide short, quick, bursts of current, but if you use that all the time and you also have other extra applications, then you would want a new battery or an extra battery. If you have a large electrical amount of extra applications then you may want to consider a combination of all three. The best way to look at this is to think of your electrical system as a river. The alternator would be the source of water, the battery or capacitor would be the lake and your applications would be like water distributions plants that suck water from the lake. The alternator can provide only so much electricity. A capacitor would be considered a small pool of electricity that could quickly be drained if needed and quickly refilled. A battery is more like a lake where you can provide lots of electricity continuously for long periods of time but it takes longer to fill up.

4. Capacitors, Batteries, Wire Gauges, and Fuses (Large Stereo Application)
When installing a capacitor or extra battery then you need to take into consideration that you don’t want to change the voltage of the system. By adding a battery in series, then you increase the voltage, by adding it in parallel the voltage stays the same and the current increases. When you add a battery or capacitor, you want to connect both positive terminals together and the negative terminal to the chassis. This will create a parallel connection.

Depending on the type of battery or capacitor (specifically how strong), is how you will determine how thick the wire needs to be between each. As a general rule of thumb, you don’t want to use anything less than 4 AWG (American Wire Gauge). By using a thicker wire, you reduce the amount of resistance in the connection. When you start using 2 farad capacitors or deep cycle batteries, then you’re going to want a thicker gauge than 4 AWG. You will never need anything thicker than 0 AWG. The biggest difference is price. Typically you will see about a $0.50 difference between 4 AWG, 2 AWG and 0 AWG. Choosing the right size is easy. 4 AWG is great for most applications under 2000 watts. When you start going over 2000 watts, you’re going to need stronger batteries or capacitors. This will also call for thicker wire. 4 AWG will work but it won’t be as efficient as 2 AWG or 0 AWG. I only recommend 0 AWG for applications over 10000 watts.

Wire size for subwoofers is something that I see constantly debated. When it comes to normal applications, your typical 18 AWG to 16 AWG wire will be more than enough to handle most 2000 watt amplifier to speaker combinations. When using a subwoofer or speaker under 800 watts then 18 AWG is all you need for great sound. When using a subwoofer that will be pulling more than 5000 watts, then you may want to consider using 14 AWG. There’s no reason to go any bigger than that.

Now on to the fun part, alternators!

Alternators
Lots of people think that by changing the alternator that this will eliminate all your electrical problems. This is not always true. A higher output alternator is a great way to stop dimming headlights when you've added one or maybe two extra electrical upgrades. The problem with upgrading the alternator is that it isn't always as easy as adding a capacitor or second battery and it isn't an all in one problem solver for all electrical problems. If you have several electrical upgrades (ex. high power headlights, large stereo system, and neons) then you are going to need somewhere to store all that electricity untill it's ready to be used. When you start getting into even larger electrical systems, you may want to add a second alternator to your setup. This can be very costly due to the need to fabricate custom parts. I only recommend adding a second alternator if the stereo system you have is rated at more than 10,000 watts. When you start using larger electrical circuits, you will drain your power sources much quicker meaning that you will need to fill them up faster to stay at normal levels and operate for longer times.

Grounding Kits
Flow of electrons can be limited by how much room there is for travel. By expanding the path of travel you decrease the resistance of the flow. Electrons flow from negative to positive. (There is another theory about electrical flow called the Holes Theory. Check my thread for more on the subject.) Electricity is the movement of electons from an atom whose outer shell is less than half full to an atom that has an outer shell that is over half full. Anyone who has some general science relating to the structure of atoms should understand what these shells are. Electrons have a negative charge thus the reason for a negative terminal on the battery. By attaching the negative terminal of the battery to the chassis you do two things, you eliminate the need to run wires for the negative portion of the circuit to every application by providing electrons to the metal of the chassis which can be accessed anywhere in the car.

Resistance in an electrical circuit decreases voltage (resistance of wires is usually not a measurable amount or an amount of any real concequence but a noticable amount if the requirement for voltage is great enough.) Voltage in an electrical motor is the equivilant to torque on your engine. The more torque you have the faster you reach your top speed (also works inconjunction with hp to allow for a higher top speed). When you use the starter on the vehicle you are using every available electron and want as much 'torque' as possible to get the engine cranked faster. This is why all your accesories turn off. It keeps the maximum amount of electrons available to be used by the starter.

This is the same reason there is a rating for watts on amp kits. If the main power wire isn't thick enough to carry all the electrons nescesary back to the battery then it could damage your amplifier by casuing it to run at less than optimal performance. By adding a grounding kit you essentially increase the amount of paths available for the electrons to travel allowing for better spark in the engine.

THE HOLES THEORY
Previously I explained that electricity is the flow of electrons from from an oversaturated atom (one with less than a half full outer shell) to an undersaturated atom (one with more than a half full outer shell). This is know as the Electron Theory for electrical current. Before I post the holes theory I want to make it undoubtebly clear that I do not believe this theory to be usefull or worth the time to know. I will explain my opinion later.

The holes theory for flow of electricity is to say that rather than an electron passing from one atom to another that instead a hole passes from one atom to another. If you were able to watch a group of atoms that were passing electricity then it would appear that a hole was passed from one atom to another.

Now to expain my opinion. I don't believe that it is possible to pass something that isn't there. A hole is simply a word that represents the absence of an object. In this case the electron. You can't pass something that doesn't physically exsist.



If anyone has any electrical questions or sees something that I missed, please post and I’ll respond as soon as I can.

[hany]

nice and rich theard , it can be refrance in the trouble , thank you alot

[fiberglasscivic]

Bizzump. Guess people are only looking on page one for help on their probs. Please search or a mod please sticky this.

[nitebeest]

Awesome write up. Even though I'm already pretty good with electrical, this definately explains a lot. This should definately be stickied. It'd help out a lot of people new to electrical and wiring.

[eurobeaner]

sticky icky!!!!!