Datasheet

1/20/2018 Resistors - learn.sparkfun.com
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16 143 32 210 48 309 64 453 80 665 96 976
The letter at the end represents a multiplier, matching up to something on this table:
LetterMultiplier LetterMultiplier LetterMultiplier
Z 0.001 A 1 D 1000
Y or R 0.01 B or H 10 E 10000
X or S 0.1 C 100 F 100000
So a 01C resistor is our good friend, 10kΩ (100x100), 01B is 1kΩ (100x10), and 01D is 100kΩ. Those are easy, other codes may not be. 85A from the picture above is 750Ω
(750x1) and 30C is actually 20kΩ.
Power Rating
The power rating of a resistor is one of the more hidden values. Nevertheless it can be important, and it’s a topic that’ll come up when selecting a resistor type.
Power is the rate at which energy is transformed into something else. It’s calculated by multiplying the voltage difference across two points by the current running between
them, and is measured in units of a watt (W). Light bulbs, for example, power electricity into light. But a resistor can only turn electrical energy running through it into heat.
Heat isn’t usually a nice playmate with electronics; too much heat leads to smoke, sparks, and fire!
Every resistor has a specific maximum power rating. In order to keep the resistor from heating up too much, it’s important to make sure the power across a resistor is kept
under it’s maximum rating. The power rating of a resistor is measured in watts, and it’s usually somewhere between ⅛W (0.125W) and 1W. Resistors with power ratings of
more than 1W are usually referred to as power resistors, and are used specifically for their power dissipating abilities.
Finding a resistor’s power rating
A resistor’s power rating can usually be deduced by observing its package size. Standard through-hole resistors usually come with ¼W or ½W ratings. More special purpose,
power resistors might actually list their power rating on the resistor.
These power resistors can handle a lot more power before they blow. From top-right to bottom-left there are examples of 25W, 5W and 3W resistors, with values of 2Ω, 3Ω
0.1Ω and 22kΩ. Smaller power-resistors are often used to sense current.
The power ratings of surface mount resistors can usually be judged by their size as well. Both 0402 and 0603-size resistors are usually rated for 1/16W, and 0805’s can take
1/10W.
Measuring power across a resistor
Power is usually calculated by multiplying voltage and current (P = IV). But, by applying Ohm’s law, we can also use the resistance value in calculating power. If we know the
current running through a resistor, we can calculate the power as:
Or, if we know the voltage across a resistor, the power can be calculated as:
Series and Parallel Resistors
Resistors are paired together all the time in electronics, usually in either a series or parallel circuit. When resistors are combined in series or parallel, they create a total
resistance, which can be calculated using one of two equations. Knowing how resistor values combine comes in handy if you need to create a specific resistor value.
Series resistors
When connected in series resistor values simply add up.
N resistors in series. The total resistance is the sum of all series resistors.