To start this off, it is important for everyone to understand some simple electrical engineering concepts. Electricity is simply the flow of electrons from one place to another. There are two things that describe how the electrons flow. One is how much force is driving the electrons to flow. This is what voltage is. The next concept is basically how fast are the electrons flowing. This is similar to current. Imagine that you have a water hose. Water flowing through the hose would be the electrons. If you turn up the pressure, the water will flow faster. The pressure would be the voltage, and the flow rate would be the current, which is measured in amperes.
There is a fundamental equation that has to be known for any circuits. It is Ohm’s law. It states that the voltage in a circuit, or accross a component is equal to the current times the resistance, or V=IR. If you look at the top picture you see that there is a simple circuit with a 5 volt power supply, and a 100 ohm resistor. The voltage drop across the resistor is going to be 5 v. To find the current through the resistor you simply divide the 5v by the 100 ohms, and find that it is 0.05A or 50mA.
In the bottom picture, you see a diode being used as a voltage regulator. The diode keeps a constant o.7v drop regardless of the current (within the range of the diodes specs). To calculate this current you find the voltage drop across the resistor which is now 5-0.7v, which is 4.3v. The new current will be 43mA.
This is important for several purposes. Lets say you wanted to make a 3.6v power supply, and only have one 7805 5v regulator. If you put two diodes in series connected to the output of the 5v regulator, you would then drop 1.4 volts, which would give you 3.6v. This is just a brief intro to calculating currents and voltages in a circuit. It is important to understand this because resistors, and components need to be rated for the current going through them.
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[...] I know that starting out in Electronics can be intimidating. There is a lot that you have to understand in order to really get a grasp of electronics. Sure, you can find some schematics, and put them together, but without understanding what resistor to put with a LED, and why you pick that resistor for that LED, then you can’t really do much except for just copy other people’s designs. I decided to find a few links for everyone to go to that will help them understand circuits, and circuit design. The first site that I go to a lot is allaboutcircuits.com. This is an invaluable resource. This site does a very good job of walking you through all of the steps from the beginning of understanding basic voltage theory to using advanced ICs. The next site that I found helpful is electronics-tutorials.com. This is a good basics tutorial that defines a lot of the terms used in electronics, such as resistance, and capacitance, and voltage. He starts out with electron theory, and moves from there. I highly suggest anyone starting out in electronics to read this. It is very important to understand these terms. It is also important to know basic circuit analysis. I have written a very basic post on this. If you know V=IR, then you can do most simple things. When picking a resistor for an LED, it is important to know your voltage source, and the voltage and current requirements for the LED. You then re-arrange this equation for R, which is R=V/I, (Resistance=voltage/current). This is the value of resistor that you would use. It is also important to know how to read a schematic. All of those symbols can be overwhelming. There is help though. http://www.kpsec.freeuk.com/symbol.htm is a site that gives a good list of circuit symbols for anyone looking for help. It doesn’t have a resistor symbol, which I found strange, so here is another site with more common components. Anyway, I hope this is something simple to get most people started. One of the best resources in DIY electronics is the chance to ask others questions. It is much easier to learn from others than by yourself. Come to DIY Live Forums, and feel free to ask any questions you have. [...]