Editing Passives
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Latest revision | Your text | ||
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+ | acelrolt | ||
{{stub}} | {{stub}} | ||
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Uses: | Uses: | ||
− | * ac coupling | + | * ac coupling â- blocking -- isolation |
* timing | * timing | ||
* Time for a capacitor to charge or discharge is very roughly RC where R is the resistor in series with the capacitor. | * Time for a capacitor to charge or discharge is very roughly RC where R is the resistor in series with the capacitor. | ||
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== Inductors == | == Inductors == | ||
− | An inductor reacts to current, but not to its value, but rather its change. It | + | An inductor reacts to current, but not to its value, but rather its change. It âtriesâ to keep the current through it constant. Any change in current causes a voltage across the inductor. The key equation for an inductor ( it is a bit complicated, but anyway here it ) is: |
=== equation here soon === | === equation here soon === | ||
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When a resistor is in series with a circuit the voltage across it will vary with the current ( ohms law ) Sometimes we do this with a low value of resistance and use the voltage across the resistor to measure or control the current. | When a resistor is in series with a circuit the voltage across it will vary with the current ( ohms law ) Sometimes we do this with a low value of resistance and use the voltage across the resistor to measure or control the current. | ||
*Isolation : | *Isolation : | ||
− | A resistor between but connecting 2 components will tend to equalize their voltage, but only using small currents. It the components | + | A resistor between but connecting 2 components will tend to equalize their voltage, but only using small currents. It the components âwant to go there own way, voltage wiseâ all they need do is put out a small current. For example people will sometimes ground themselves through a 10 mega ohm resistor. This tends to bring them to ground voltage, but they are protected from a deadly shock because most voltages cannot push a lethal current through 10 megs. |
*pull up or pull down: | *pull up or pull down: | ||
Sometimes a component will have a very high resistance to both the positive and negative side of the power supply and the voltage can easily drift around due to more or less random events. Under these conditions we will often connect a resistance ( typically around 10 K ohms ) to either the positive or negative side of the power supply. If to the positive side it is called a pull up resistor, if to the negative side a pull down resistor. | Sometimes a component will have a very high resistance to both the positive and negative side of the power supply and the voltage can easily drift around due to more or less random events. Under these conditions we will often connect a resistance ( typically around 10 K ohms ) to either the positive or negative side of the power supply. If to the positive side it is called a pull up resistor, if to the negative side a pull down resistor. | ||
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*Adjustable voltage divider. | *Adjustable voltage divider. | ||
*Volume control. | *Volume control. | ||
− | *Variable resistor ( sometimes used when the correct value of resistance is not know or available, then the pot is use: it is adjusted, perhaps just once, after the circuit is built | + | *Variable resistor ( sometimes used when the correct value of resistance is not know or available, then the pot is use: it is adjusted, perhaps just once, after the circuit is built â to âtweakâ the circuit into operating correctly. |
*Trim or 0 adjustment | *Trim or 0 adjustment | ||