How to choose LED bulbs?

How to choose LED bulbs?

There are many kinds of LED bulbs with different parameters, so it is necessary to clarify which one it is.

LED bulbs that are often used as indicator lights (as shown in the figure below, not the current high-brightness lighting LEDs):

This kind of LED bulbs often appear on the indicator lights of various toys and sockets.

Working current: The working current is 1-20mA, and the brightness becomes brighter with the increase of the current.

Forward voltage drop: Most are around 1.7-2V.

The voltage of the plug-in strip is 220V. If this kind of LED is used as an indicator light, the current brightness of 1-2mA is enough, and the power of the current-limiting resistor connected in series can also be as small as possible. In addition, it is suggested that a rectifier diode (1N4007) be connected in series with the LED on the 220V circuit, which can effectively prevent the peak voltage from breaking down the  LED bulbs .

Calculation method of series resistance R and its power:

R=110V/1mA (or 2mA)=110K ohms (or 55K ohms)

【Note】110V is the voltage after rectifier diode chopping. Power = 110Vx 1mA (or 2mA) = 0.11W (or 0.22W)

[A LED bulb with a resistance of 0.25W can be selected. In order to save costs, the commercially available plug-in strips often use 0.125W resistors, so they often burn out]