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Power 5V LED lamp 3V 20mA need to connect how much resistance calculation formula
In case of current limiting and step-down of series resistance:
The voltage drop on the resistance is 5 - 3 = 2V
The rated current is 20mA. Generally, the working current of 10 ~ 15mA is enough. Therefore, the resistance R should be greater than = u / I = 2 / 0.015 = 133.33 Ω
From the point of view of common resistance, 150 Ω can be selected. At this time, the power is U & # 178 / r = 2 × 2 △ 150 = 0.0267w, so it is enough to select 0603 or above chip or 0.25W or above in-line package
The voltage of bright light-emitting diode has a few kinds of a few volts. Connect 220 volt electricity to want string how big resistance, formula how to calculate
Led depends on the color and voltage. For example, the common red is 1.8V, the blue one is 3V, and the current is 10mA. According to the brightness requirement, a 100-200k1 / 2W resistor is connected in series in the 220V AC voltage. I usually connect a 10k resistor in the 12V voltage. If you connect a 1K resistor in the 220V voltage, the LED will flash
How to calculate the resistance of LED string? Don't tell me how large the resistance of several light strings is, I still need the formula Thank you!
For example, if the working voltage is 12V and three LEDs work in series, the voltage drop of each LED is 2.5V and the voltage drop of the three LEDs is 7.5V, then 12-7.5 / 0.02 = 225. Choose the nominal resistance of 220 Ω. Among them, 20mA is the normal working current of the LED. By analogy, others can also be calculated in this way
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