A major problem when working with LEDs, is particularly novices connecting the LED to the circuit, or how to calculate the value of resistance used. Currently LEDs are very efficient, common and therefore the current needed to illuminate them is quite low: 5mA or less for the LED indicators and 20mA for high brightness LEDs. LEDs are relatively tolerant stream so it can vary between 5mA and 15mA for LED common between 15mA and 30mA for LED high brightness.
The formula for calculating the resistance is obtained by Ohm's law and is as follows:
R = (V - V-LED) / I
wherein:
R = resistance
V = voltage
V-LED = LED voltage typical (varies according to whether the LED)
I = current
HI is the current through the LED For example, if we have a red LED connected to 12V with a current of 5mA: R = (12V - 1.2V) / 5mA = 2160 ohms (using default values of resistance: 2.200 ohm)
Calculation base resistors for High Brightness LEDs for voltage 12 Volts
LED Blue and White
Vled v 3.70
current 20mA
Results Resistance: 415 Ohms - 390 Ohms = Approximate
Red LED
Vled v 1.20
current 20mA
Results Resistance: 540 Ohms - 560 Ohms = Approximate
Calculation base resistors for LEDs for normal tension 12 Volts
Red LED
Vled v 1.20
current 5mA
Results Resistance: 2160 Ohms - Approximate = 2k2 Ohms
Green and yellow LED
Vled v 1.60
current 20mA
Results Resistance: 540 Ohms - 560 Ohms = Approximate
Calculation base resistors for High Brightness LEDs for voltage 5 Volts
LED Blue and White
Vled v 3.70
current 20mA
Result of resistance: 65 Ohms - 68 Ohms = Approximate
Red LED
Vled v 1.20
current 20mA
Results Resistance: 190 Ohms - 180 Ohms = Approximate
Calculation base resistors for LEDs to normal voltage 5 Volts
Red LED
Vled v 1.20
current 5mA
Results Resistance: 760 Ohms - 680 Ohms = Approximate
Green and yellow LED
Vled v 1.60
current 20mA
Results Resistance: 680 Ohms - 680 Ohms = Approximate
Take into consideration that there are hundreds of types of LEDs, we just showing the calculation of resistance of LEDs Basic.
There are three types of LEDs:
LED Low current
Typically rated for 2 mA at around 2 V (approximately 4 mW consumption).
LED Standard, Common or Indicator
20 mA LEDs (up to 90 mW) at about:
1.9-2.1 V for the red, orange and yellow,
3.0-3.4 V for green and blue,
2.9 to 4.2 V to violet, pink, purple and white.
High Brightness LED
20 mA at about 2 V or 4-5 V, designed for viewing in direct sunlight.
LED Blue and White
Vled v 3.70
current 20mA
Results Resistance: 415 Ohms - 390 Ohms = Approximate
Red LED
Vled v 1.20
current 20mA
Results Resistance: 540 Ohms - 560 Ohms = Approximate
Calculation base resistors for LEDs for normal tension 12 Volts
Red LED
Vled v 1.20
current 5mA
Results Resistance: 2160 Ohms - Approximate = 2k2 Ohms
Green and yellow LED
Vled v 1.60
current 20mA
Results Resistance: 540 Ohms - 560 Ohms = Approximate
Calculation base resistors for High Brightness LEDs for voltage 5 Volts
LED Blue and White
Vled v 3.70
current 20mA
Result of resistance: 65 Ohms - 68 Ohms = Approximate
Red LED
Vled v 1.20
current 20mA
Results Resistance: 190 Ohms - 180 Ohms = Approximate
Calculation base resistors for LEDs to normal voltage 5 Volts
Red LED
Vled v 1.20
current 5mA
Results Resistance: 760 Ohms - 680 Ohms = Approximate
Green and yellow LED
Vled v 1.60
current 20mA
Results Resistance: 680 Ohms - 680 Ohms = Approximate
Take into consideration that there are hundreds of types of LEDs, we just showing the calculation of resistance of LEDs Basic.
There are three types of LEDs:
LED Low current
Typically rated for 2 mA at around 2 V (approximately 4 mW consumption).
LED Standard, Common or Indicator
20 mA LEDs (up to 90 mW) at about:
1.9-2.1 V for the red, orange and yellow,
3.0-3.4 V for green and blue,
2.9 to 4.2 V to violet, pink, purple and white.
High Brightness LED
20 mA at about 2 V or 4-5 V, designed for viewing in direct sunlight.
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