Light emitting diodes require a number of wiring rules to be followed regarding polarity, current limiting, and surge protection. Neglect of these rules leads to premature, if not instantaneous failure of devices.
Instructions
Step 1
Always turn on LEDs in straight polarity only. Some of them fail even when a relatively small reverse voltage is applied. There are, however, such LEDs that are capable of exhibiting the properties of a zener diode when a reverse voltage is applied (not to be confused with the properties of a stabilizer, which they have when applying a forward voltage).
Step 2
Do not exceed the forward current of the LED. If you don't know it, use a simple rule: pass a current of no more than 3 mA through any SMD LED, no more than 10 mA through a regular indicator LED, and no more than 20 mA through a lighting LED.
Step 3
When calculating the current limiting resistor for an LED, take the voltage drop across the LED into account. For an infrared LED it is 1.4 V, for red it is 1, 7, for yellow or green it is about 2, for blue, blue-green, violet and white it is about 3, 5. Subtract this drop from the power supply voltage, and you will get the voltage drop across the resistor itself. Further, the calculation of its value depending on the desired current through the diode, guided by the usual formula of Ohm's law: R = U / I.
Step 4
In the event that several LEDs are connected in series, add the values of the voltages falling on them with each other. Connect in series only LEDs designed for the same current, or better - generally of the same type.
Step 5
Only connect LEDs with the same voltage drop in parallel. In all other cases, put a separate resistor on each of the LEDs.
Step 6
To protect the LEDs from voltage surges in those circuits, where possible, connect in parallel to each of them in reverse polarity with a zener diode for a voltage of 6 V. Such a zener diode will protect the diode from voltage surges of any polarity, and, at the same time, it will not bypass, which means that it will not interfere with its normal operation at all.
