Every year, LEDs are increasingly used, they are beginning to be actively used as light sources. If it becomes necessary to independently connect the LED, certain rules should be followed when performing this work.
It is necessary
- - multimeter (tester);
- - power supply;
Instructions
Step 1
To connect an LED, you need to know its characteristics. Usually LEDs are rated for 20mA current, the nominal voltage depends on the color of the light. For red and yellow LEDs, this is 2 V (valid range 1, 8 - 2, 4 V). For white, green and blue 3 V (3 - 3.5 V). When connecting the LED, it is important to accurately set the current consumption - 20 mA. In this case, the LED will work properly for many years.
Step 2
Before connecting the LED, the power supply should be selected. So, if for white, green and blue LEDs two series-connected finger-type batteries for 1.5 V will give a total of 3 V, then the required supply voltage should not exceed the maximum value of 3.5 V. But if you turn on red or yellow with two batteries LED, it may just burn out. That is why take a responsible approach to the choice of a power source, make sure that the voltage on the LED does not exceed the permissible value.
Step 3
If the voltage exceeds the required one, a damping resistor should be included in the circuit. For example, you want to connect a 2 V LED to a 9 V power supply. It turns out an extra 7 V. To extinguish them, using the formula R = U / I, you can determine that the required resistance is 7 V / 0, 02 A, or 350 Ohm …
Step 4
Heat is generated on the damping resistor, so it must have the required power. Calculate it using the formula P = U * I. We substitute the data: 7 V * 0.02 A = 0.14 W. This means that you need a resistor of about 0.2 W - it is better to take with some margin.
Step 5
When using an LED, it is important in practice to select a current no higher than 20 mA. To do this, turn on the tester in the open circuit and check the current strength. If it is slightly less than 20 mA - for example, 17-18, then leave it that way. The LED will shine a little less brightly, but it will work for a very long time. If the current is much lower or higher, you should adjust it by changing the resistance of the additional resistor.
Step 6
Pay attention to the polarity of the LED connection, incorrect connection may damage it. The anode is connected to the plus of the power supply, the cathode to the minus. A flat area (cut) is made on the side of the cathode on the LED bulb. In addition, the cathode has a shorter lead.
Step 7
If you want to power an LED or a string of LEDs from the AC mains, then take care of rectifying the voltage. In the simplest case, a diode with a breakdown voltage of at least 400 V can be included in the circuit.
