In the United States, the power provided to our homes is AC with about 170V zero-to-peak (amplitude) and 60Hz (frequency). We can turn to our trusty outlet for a good example of how an AC waveform works. For simplicity, we sill assume that phase is 0° for the rest of this tutorial. Because of the periodic nature of the sine wave, if the wave form is shifted by 360° it becomes the same waveform again, as if it was shifted by 0°. It is often given as a number between 0 and 360 and measured in degrees. Phase is a measure of how shifted the waveform is with respect to time. T is our independent variable: time (measured in seconds). The frequency tells how many times a particular wave form (in this case, one cycle of our sine wave - a rise and a fall) occurs within one second. This is given in the form of hertz or units per second. The sin() function indicates that our voltage will be in the form of a periodic sine wave, which is a smooth oscillation around 0V.Ģπ is a constant that converts the freqency from cycles (in hertz) to angular frequnecy (radians per second).į describes the frequency of the sine wave. This describes the maximum voltage that our sine wave can reach in either direction, meaning that our voltage can be +V P volts, -V P volts, or somewhere in between. The equation to the right of the equals sign describes how the voltage changes over time. V(t) is our voltage as a function of time, which means that our voltage changes as time changes. Voltage, Current, Resistance, and Ohm's Law.Some examples of AC and DC applications.
AC also has some useful properties, such as being able to convert voltage levels with a single component (a transformer), which is why AC was chosen as the primary means to transmit electricity over long distances. Most homes are wired for AC, so if you plan to connect your Tardis music box project to an outlet, you will need to convert AC to DC. However, it is important to understand some AC concepts. Most of the digital electronics that you build will use DC. The voltage in AC circuits also periodically reverses because the current changes direction. Electric charge in alternating current (AC), on the other hand, changes direction periodically. In direct current (DC), the electric charge (current) only flows in one direction. There is also the less popular center negative (-) connector.Where did the Australian rock band AC/DC get their name from? Why, Alternating Current and Direct Current, of course! Both AC and DC describe types of current flow in a circuit. The most common is center positive (+) connectors. Once you have the V and A determined, most appliances will have a circular connector with the inside hole carrying one pole and the outside carrying the other. Usually, all of this info is on the adapter sticker, remember you are always looking for the output V and mAh or A. The plug fits into your device and has the correct polarity.The adapter output is greater or equal to the devices rated mAh or A.The adapter output V matches the rated input V of the device.Inspect the device and look for any labels or symbols that indicate either the voltage or mAh/A, if not, check the user manual or do a quick Google search.Ĭhoose the right specs by matching the V and equal or beat the mAh, so if you are choosing an AC adapter, make sure you check the following: Various output voltage & current combinations.
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