where can I get a schematic?

1 ANSWERS

1. amomipais82
   

   Hi,
   n general terms, a circuit can be described as any group of electrical or electronic devices connected together by conductors. Conductors are most often metallic, and wires were the conductor of choice in the past. Old radios and other electronic equipment were often a rat's nest of wires. Today, it's more common to find metallic pathways, often called traces, on a board constructed of a mixture of fiberglass and epoxy. The terms board and card are interchangeable.
   
   A schematic in electronics is a drawing representing a circuit. It uses symbols to represent real-world objects. The most basic symbol is a simple conductor, shown simply as a line. If wires connect in a diagram, they are shown with a dot at the intersection:
   
   
   Conductors that do not connect are shown without a dot, or with a bridge formed by one wire over the other:
   
   
   Among the connections are power and ground, the high and low system voltages respectfully. The 5 volt system power in the schematic is shown simply as 5V. There is also a +12V supply and a -12V supply. Ground, or 0 volts, has its own symbol:
   
   
   A switch is a device that is capable of allowing the user to break the circuit as if the wire had been broken. Its symbol reflects this characteristic:
   
   The three switches in the diagram are grouped in a Dual In-line Package (DIP).
   
   A resistor is a device that resists the flow of charge. Its symbol reflects this characteristic by making the line jagged:
   
   Just in case you have seen "flow of current" elsewhere rather than "flow of charge", see "Science Myths" in K-6 Textbooks and Popular culture and the definition of current below.
   
   The unit of resistance is the ohm, pronounced om with a long o. The K in the schematics stands for kilohm or thousands of ohms. 10K means the same as 10,000. Meg and sometimes M mean megohm or million ohms. 4.7Meg or 4.7M is the same as 4,700,000.
   
   You will see two variations on resistors in the schematic. One is the resistor array or network. It is a Single In-line Package (SIP) containing several resistors connected together. They can be found in many configurations. The one used here simply connects one end of the resistors to each other and brings them out to a common connection. The other end of each resistor is left free. Another variation is the variable resistor. It has a third contact that can move along the resistor element to permit the values at that point to be variable. The moveable part is called the wiper and is shown as an arrow.
   
   There is a relationship between voltage, current and resistance that is expressed by Ohm's Law, which says that Voltage is equal to Current times Resistance, or:
   
   V = I * R
   
   V is voltage (often referred to as Electromotive Force where E rather than V is used), I is current and R is resistance. Current is expressed in Amperes, or amps for short. Very little current is used in typical electronic circuits, so milliamps, which means 1/1000 amp, is used. One milliamp = .001 amp. It's abbreviated ma, or sometimes MA.
   
   To paraphrase a definition of charge from whatis.com :
   
   "The coulomb (symbolized C) is the standard unit of electric charge in the International System of Units (SI). It is a dimensionless quantity. A quantity of 1 C is equal to approximately 6.24 x 1018, or 6.24 quintillion."
   
   "In terms of SI base units, the coulomb is the equivalent of one ampere-second. Conversely, an electric current of 1 amp represents 1 C of unit electric charge carriers flowing past a specific point in 1 second. The unit electric charge is the amount of charge contained in a single electron. Thus, 6.24 x 1018 electrons have 1 C of charge. This is also true of 6.24 x 1018 positrons or 6.24 x 1018 protons, although these two types of particles carry charge of opposite polarity to that of the electron."
   
   Since we deal mostly with electrons in electronics, 1 amp represents the effect of 6,240,000,000,000,000,000 electrons flowing past a point per second. Thus, since current is already defined as something flowing, to say "current flow" would be to say "..... flowing flow" which is incorrect because it is redundant.
   
   Now let's say we have a 10K resistor and 2 milliamps of current. The voltage across the resistor will be:
   
   V = 10,000 * .002 = 20 volts
   
   We can use the above equation to generate an equation for each of the three variables. It requires remembering just two things:
   1. It's ok to do something to one side of an equation as long as the same thing is done to the other side. The two sides will remain equal.
   2. Anything divided by itself is equal to 1.
   
   Start with the original equation:
   V = I * R
   Now divide both sides by R. Since R/R = 1, the right side now becomes I * 1 which is simply I, giving us V/R = I. If we switch sides and put the I on the left we end up with:
   I = V/R
   
   Again, start with the original equation:
   V = I * R
   Now divide both sides by I. Since I/I = 1, the right side now becomes R * 1 which is simply R, giving us V/I = R. If we switch sides and put the R on the left we end up with:
   R = V/I
   
   Thus, all three equations are:
   V = I * R
   I = V/R
   R = V/I
   
   One way to remember the three equations is to say, "The Vulture looks down and sees the Iguana and the Rabbit side by side (V = I * R), the Iguana sees the Vulture over the Rabbit (I = V/R) and the Rabbit sees the Vulture over the Iguana (R = V/I)."

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