How To Find A Short In 12v System

Thunderstruck!

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Where did the Australian rock band AC/DC get their proper noun from? Why, Alternate Current and Direct Current, of course! Both AC and DC describe types of electric current flow in a circuit. In direct current (DC), the electrical charge (current) merely flows in one direction. Electrical charge in alternating current (AC), on the other manus, changes management periodically. The voltage in AC circuits also periodically reverses because the current changes management.

Most of the digital electronics that you build will utilise DC. Notwithstanding, information technology is important to understand some Air conditioning concepts. Most homes are wired for Air conditioning, then if yous plan to connect your Tardis music box project to an outlet, y'all will demand to catechumen Air-conditioning to DC. Air-conditioning besides has some useful backdrop, such as being able to convert voltage levels with a single component (a transformer), which is why AC was chosen as the primary ways to transmit electricity over long distances.

What You Will Acquire

The history behind Air conditioning and DC
Different ways to generate Air conditioning and DC
Some examples of Air conditioning and DC applications

Alternating Current (Ac)

Alternate electric current describes the flow of charge that changes direction periodically. As a result, the voltage level also reverses along with the current. Air-conditioning is used to deliver power to houses, office buildings, etc.

Generating Ac

Air conditioning tin be produced using a device called an alternator. This device is a special blazon of electrical generator designed to produce alternate electric current.

A loop of wire is spun inside of a magnetic field, which induces a current along the wire. The rotation of the wire can come up from any number of means: a air current turbine, a steam turbine, flowing water, and then on. Because the wire spins and enters a dissimilar magnetic polarity periodically, the voltage and current alternates on the wire. Here is a short blitheness showing this principle:

(Video credit: Khurram Tanvir)

Generating AC tin be compared to our previous h2o analogy:

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To generate AC in a set up of water pipes, we connect a mechanical creepo to a piston that moves h2o in the pipes back and along (our "alternating" current). Detect that the pinched department of pipe however provides resistance to the flow of h2o regardless of the direction of menses.

Waveforms

AC can come in a number of forms, as long as the voltage and current are alternating. If we hook upwardly an oscilloscope to a circuit with AC and plot its voltage over time, we might see a number of different waveforms. The about common blazon of Ac is the sine moving ridge. The Air conditioning in near homes and offices have an oscillating voltage that produces a sine wave.

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Other common forms of Air conditioning include the foursquare wave and the triangle wave:

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Square waves are frequently used in digital and switching electronics to test their operation.

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Triangle waves are establish in sound synthesis and are useful for testing linear electronics like amplifiers.

Describing a Sine Wave

Nosotros oft desire to describe an AC waveform in mathematical terms. For this case, we will use the mutual sine wave. At that place are 3 parts to a sine wave: amplitude, frequency, and stage.

Looking at just voltage, we can describe a sine wave as the mathematical part:

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V(t) is our voltage as a function of time, which means that our voltage changes equally time changes. The equation to the right of the equals sign describes how the voltage changes over time.

V_P is the amplitude. This describes the maximum voltage that our sine moving ridge can reach in either management, pregnant that our voltage can be +V_P volts, -V_P volts, or somewhere in between.

The sin() function indicates that our voltage will be in the class of a periodic sine moving ridge, which is a smooth oscillation effectually 0V.

2π is a constant that converts the freqency from cycles (in hertz) to angular frequnecy (radians per 2d).

f describes the frequency of the sine wave. This is given in the form of hertz or units per 2nd. The frequency tells how many times a particular moving ridge form (in this case, i cycle of our sine wave - a rising and a fall) occurs inside one 2d.

t is our independent variable: time (measured in seconds). As fourth dimension varies, our waveform varies.

φ describes the phase of the sine wave. Phase is a measure of how shifted the waveform is with respect to fourth dimension. It is frequently given as a number between 0 and 360 and measured in degrees. Considering of the periodic nature of the sine wave, if the wave course is shifted by 360° it becomes the aforementioned waveform again, as if information technology was shifted past 0°. For simplicity, we sill presume that phase is 0° for the remainder of this tutorial.

We can plow to our trusty outlet for a good case of how an AC waveform works. In the United States, the power provided to our homes is AC with virtually 170V goose egg-to-summit (amplitude) and 60Hz (frequency). We can plug these numbers into our formula to get the equation (call back that we are assuming our phase is 0):

AC equation

We can use our handy graphing calculator to graph this equation. If no graphing calculator is available we tin can use a costless online graphing program like Desmos (Note that y'all might accept to use 'y' instead of '5' in the equation to see the graph).

AC_sinewave

Find that, every bit we predicted, the voltage ascent up to 170V and downwards to -170V periodically. Additionally, 60 cycles of the sine wave occurs every 2nd. If nosotros were to measure the voltage in our outlets with an oscilloscope, this is what we would see (WARNING: do not attempt to measure the voltage in an outlet with an oscilloscope! This will likely impairment the equipment).

NOTE: You might have heard that AC voltage in the US is 120V. This is besides correct. How? When talking about Air conditioning (since the voltage changes constantly), it is ofttimes easier to use an average or hateful. To accomplish that, we use a method called "Root hateful squared." (RMS). It is oftentimes helpful to use the RMS value for Air conditioning when you lot want to calculate electric power. Even though, in our example, we had the voltage varying from -170V to 170V, the root hateful foursquare is 120V RMS.

Applications

Home and office outlets are almost always Ac. This is because generating and transporting AC across long distances is relatively easy. At loftier voltages (over 110kV), less energy is lost in electrical ability transmission. Higher voltages hateful lower currents, and lower currents hateful less heat generated in the power line due to resistance. AC tin be converted to and from loftier voltages hands using transformers.

Air-conditioning is as well capable of powering electrical motors. Motors and generators are the verbal aforementioned device, just motors convert electrical free energy into mechanical energy (if the shaft on a motor is spun, a voltage is generated at the terminals!). This is useful for many large appliances similar dishwashers, refrigerators, and then on, which run on Air conditioning.

Direct Electric current (DC)

Direct electric current is a chip easier to sympathise than alternating current. Rather than oscillating dorsum and forth, DC provides a constant voltage or current.

Generating DC

DC can exist generated in a number of ways:

An Ac generator equipped with a device called a "commutator" can produce straight current
Use of a device called a "rectifier" that converts Air conditioning to DC
Batteries provide DC, which is generated from a chemic reaction within of the battery

Using our water illustration again, DC is like to a tank of water with a hose at the end.

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The tank can just push water one style: out the hose. Similar to our DC-producing battery, once the tank is empty, water no longer flows through the pipes.

Describing DC

DC is defined equally the "unidirectional" menstruum of current; current only flows in ane direction. Voltage and current can vary over time so long as the management of flow does not modify. To simplify things, we will assume that voltage is a constant. For example, we assume that a AA bombardment provides 1.5V, which can be described in mathematical terms as:

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If nosotros plot this over time, we see a constant voltage:

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What does this mean? Information technology means that we can count on nigh DC sources to provide a constant voltage over time. In reality, a battery volition slowly lose its charge, meaning that the voltage will drop as the battery is used. For near purposes, we can assume that the voltage is constant.

Applications

Almost all electronics projects and parts for auction on SparkFun run on DC. Everything that runs off of a battery, plugs in to the wall with an AC adapter, or uses a USB cable for ability relies on DC. Examples of DC electronics include:

Cell phones
The LilyPad-based D&D Die Gauntlet
Flat-screen TVs (Ac goes into the TV, which is converted to DC)
Flashlights
Hybrid and electrical vehicles

Battle of the Currents

About every abode and business is wired for AC. Withal, this was not an overnight conclusion. In the late 1880s, a variety of inventions beyond the Usa and Europe led to a full-calibration battle between alternate current and direct current distribution.

In 1886, Ganz Works, an electric company located in Budapest, electrified all of Rome with AC. Thomas Edison, on the other hand, had constructed 121 DC power stations in the United states by 1887. A turning signal in the battle came when George Westinghouse, a famous industrialist from Pittsburgh, purchased Nikola Tesla'southward patents for AC motors and transmission the adjacent year.

AC vs. DC

Edison

Thomas Edison (Image courtesy of biography.com)

In the late 1800s, DC could non exist easily converted to high voltages. As a result, Edison proposed a arrangement of small, local power plants that would power individual neighborhoods or city sections. Ability was distributed using three wires from the power plant: +110 volts, 0 volts, and -110 volts. Lights and motors could be connected between either the +110V or 110V socket and 0V (neutral). 110V immune for some voltage drop between the plant and the load (home, office, etc.).

Even though the voltage drib across the power lines was accounted for, power plants needed to be located within 1 mile of the end user. This limitation made power distribution in rural areas extremely hard, if not impossible.

With Tesla's patents, Westinghouse worked to perfect the Air conditioning distribution organisation. Transformers provided an inexpensive method to footstep up the voltage of Ac to several thousand volts and dorsum down to usable levels. At higher voltages, the same power could be transmitted at much lower current, which meant less power lost due to resistance in the wires. As a result, big power plants could be located many miles away and service a greater number of people and buildings.

Edison's Smear Entrada

Over the next few years, Edison ran a entrada to highly discourage the utilise of Air-conditioning in the United States, which included lobbying state legislatures and spreading disinformation about Air conditioning. Edison also directed several technicians to publicly electrocute animals with Ac in an attempt to show that Ac was more than dangerous than DC. In attempt to display these dangers, Harold P. Brownish and Arthur Kennelly, employees of Edison, designed the first electric chair for the state of New York using Air-conditioning.

The Rising of AC

In 1891, the International Electro-Technical Exhibition was held in Frankfurt, Frg and displayed the first long altitude transmission of 3-phase Air conditioning, which powered lights and motors at the exhibition. Several representatives from what would become General Electric were present and were subsequently impressed by the display. The post-obit year, General Electric formed and began to invest in Air-conditioning technology.

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Edward Dean Adams Ability Plant at Niagara Falls, 1896 (Paradigm courtesy of teslasociety.com)

Westinghouse won a contract in 1893 to build a hydroelectric dam to harness the power of Niagara falls and transmit AC to Buffalo, NY. The project was completed on Nov sixteen, 1896 and AC ability began to power industries in Buffalo. This milestone marked the decline of DC in the United States. While Europe would prefer an Air-conditioning standard of 220-240 volts at 50 Hz, the standard in North America would become 120 volts at 60 Hz.

High-Voltage Straight Electric current (HVDC)

Swiss engineer René Thury used a series of motor-generators to create a high-voltage DC system in the 1880s, which could be used to transmit DC power over long distances. Nevertheless, due to the high cost and maintenance of the Thury systems, HVDC was never adopted for almost a century.

With the invention of semiconductor electronics in the 1970s, economically transforming between AC and DC became possible. Specialized equipment could be used to generate high voltage DC ability (some reaching 800 kV). Parts of Europe have begun to employ HVDC lines to electrically connect various countries.

HVDC lines feel less loss than equivalent Air-conditioning lines over extremely long distances. Additionally, HVDC allows different AC systems (e.m. l Hz and 60 Hz) to be connected. Despite its advantages, HVDC systems are more costly and less reliable than the common Ac systems.

In the end, Edison, Tesla, and Westinghouse may have their wishes come true. AC and DC can coexist and each serve a purpose.

Resources and Going Farther

You should at present have a good understanding of the differences betwixt Air conditioning and DC. AC is easier to transform betwixt voltage levels, which makes high-voltage transmission more feasible. DC, on the other manus, is institute in most all electronics. You should know that the two do non mix very well, and y'all will demand to transform AC to DC if you wish to plug in most electronics into a wall outlet. With this agreement, you should be ready to tackle some more complex circuitry and concepts, even if they incorporate AC.

Have a look at the following tutorials when you are ready to dive deeper into the earth of electronics: