I. Introduction
In the development of the Internet of Things, we often need to light up the light-emitting diode, so in the case of high current, the LED light-emitting diode will soon be slightly, because we need to add a current-limiting resistor to limit the current.
2. Technical theory
First of all, we need to understand the principle of series voltage division and parallel shunt flow .
You can learn articles here: Resistors - Common Circuit Components - Embedded Development - Internet of Things Development
Secondly, we need to confirm the parameters of the selected LED bulbs. The LED parameters I use here are as follows:
| bulb color | Operating Voltage | Working current | pressure drop |
| red | 1.8v-2.2v | 5-10mA | 1.6v |
| yellow | 1.8v-2.2v | 5-10mA | 1.4v |
| blue | 3.0v-3.6v | 5-10mA | 1.6v |
| green | 3.0v-3.6v | 5-10mA | 1.6v |
| White | 3.0-3.6v | 5-10mA | 1.6v |
Due to the different manufacturers of LEDs, their working voltage and current are also different, the above table is for reference only.
3. Implementation method
First, we will show the required circuit diagram.
Suppose we are here a red LED light-emitting diode. According to the parameter table, we choose its voltage as 2.2v and current as 10mA. Next, we will use a current-limiting resistor to adjust the voltage and current of the LED bulb.
Embedded development formula summary: summary of commonly used circuit formulas - circuit formulas that must be met in embedded development - Internet of Things development
Ohm's Law:
According to the basic knowledge of resistors (there are learning articles above), the resistors are connected in series to divide the voltage and wait for the current. We know that the voltage is 2.2v and the current is 10MA. Then the current situation is as follows:
According to the basic knowledge of resistors, we know that resistors in series are voltage dividers. We know that the voltage of the LED bulb is 2.2v, then the voltage of the resistor is the total voltage -2.2v, that is, the voltage of the resistor is 1.1v.
Now it is known that the voltage of the resistor is 1.1v, and the current is 10mA, which is 0.01A. According to Ohm's law, R=1.1/0.01=110Ω
Then we can choose a resistor with a resistance of 110Ω, or slightly larger than 110Ω
Fourth, the power selection of the resistor
Power calculation formula:
According to the voltage and current calculated above, we can find the power of the resistor as P=1.1*0.01=0.011W
Therefore, when we choose a resistor, we can choose a resistor with a power greater than 0.011W, and we can choose a 1/8 watt resistor or above.