Ohm's Law: Difference between revisions
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[[File:Ohms-law.jpg|300px]]<br/> | [[File:Ohms-law.jpg|300px]]<br/> | ||
==Voltage '''V'''== | ==Voltage '''(V)'''== | ||
Voltage is measured in [http://en.wikipedia.org/wiki/Volt volts]. (V) There are two basic type of voltage:<br/> | Voltage is measured in [http://en.wikipedia.org/wiki/Volt volts]. (V) There are two basic type of voltage:<br/> | ||
*'''AC''' [http://en.wikipedia.org/wiki/Alternating_current Alternating Current] | *'''AC''' [http://en.wikipedia.org/wiki/Alternating_current Alternating Current] | ||
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***Many Integrated Circuits require 5 volts DC (VDC) to power them. | ***Many Integrated Circuits require 5 volts DC (VDC) to power them. | ||
==Resistance '''R'''== | ==Current '''(I)'''== | ||
Resistance is measured in [http://en.wikipedia.org/wiki/Ohm ohms] (Ω).<br/> | Current is measured in [http://en.wikipedia.org/wiki/Ampere amps] (A). Current is often measured in many electronic circuits is measured in milliamps (ma). A milliamp is one thousandth of an amp (0.01A).<br/> | ||
*Example: | |||
**A typical LED draws 20 milliamps (0.02A or 20mA). | |||
==Resistance '''(R)'''== | |||
Resistance is measured in [http://en.wikipedia.org/wiki/Ohm ohms] (Ω). Resistors are the most common form of resistance in circuits.<br/> | |||
*Example: | |||
**A common current limiting resistor for driving optoisolators is 680 ohms (Ω). | |||
==Power '''(P)'''== | |||
Power is measured in [http://en.wikipedia.org/wiki/Watt watts] (W). The common formula for Power is:<br/> | |||
::'''P=VI'''<br/> | |||
::'''Power=Voltage x Current'''<br/> | |||
*Example: | |||
**A common table lamp is 100 watts (100w). | |||
==LED Calculator== | ==LED Calculator== | ||
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===Array of LEDs=== | ===Array of LEDs=== | ||
[http://led.linear1.org/led.wiz LED Calculator] for an array of LEDs.<br/> | [http://led.linear1.org/led.wiz LED Calculator] for an array of LEDs.<br/> | ||
==Pixel Voltage Drop Calculator== | ==Pixel Voltage Drop Calculator== | ||
[http://doityourselfchristmas.com/forums/showthread.php?20242-New-tools-for-estimating-pixels-string-voltage-drops Thread]<br/> | [http://doityourselfchristmas.com/forums/showthread.php?20242-New-tools-for-estimating-pixels-string-voltage-drops Thread]<br/> | ||
[http://blinkyflashy.info/calcs/pixpower.php Calculator] | [http://blinkyflashy.info/calcs/pixpower.php Calculator] | ||
Revision as of 04:41, 28 October 2012
Ohm's Law
Ohm's Law is a formula that relates the basic electrical properties. The common formula for Ohm's Law is:
- V=IR
- Voltage = Current x Resistance
- V=IR
Ohm's Law Diagram
The following diagram shows the relationship between the various electrical properties.
Voltage (V)
Voltage is measured in volts. (V) There are two basic type of voltage:
- AC Alternating Current
- Example:
- The voltage of a typical wall power outlet in the United States is 120 volts AC (VAC).
- Example:
- DC Direct Current
- Example:
- The voltage of a typical AA battery is 1.25 volts DC (VDC).
- Many Integrated Circuits require 5 volts DC (VDC) to power them.
- Example:
Current (I)
Current is measured in amps (A). Current is often measured in many electronic circuits is measured in milliamps (ma). A milliamp is one thousandth of an amp (0.01A).
- Example:
- A typical LED draws 20 milliamps (0.02A or 20mA).
Resistance (R)
Resistance is measured in ohms (Ω). Resistors are the most common form of resistance in circuits.
- Example:
- A common current limiting resistor for driving optoisolators is 680 ohms (Ω).
Power (P)
Power is measured in watts (W). The common formula for Power is:
- P=VI
- Power=Voltage x Current
- P=VI
- Example:
- A common table lamp is 100 watts (100w).
LED Calculator
Use these calculators to calculate the resistor needed to include in a circuit with a LED.
Single LED
LED Calculator for 1 LED.
Array of LEDs
LED Calculator for an array of LEDs.