LED indicator in the switch. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Beginner radio amateur
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Probably, many are familiar with the situation when in the dark you need to turn on the light. A hand fumbles along the wall, hoping to find the switch. To avoid such situations, some models of industrial switches are equipped with LED or neon indicators that glow when the light is turned off.
If ordinary switches are installed in the apartment, then it is not difficult to equip them with LED-based indicators, one of the options of which is shown in the figure.
A single SA1 switch turns on a luminaire with a lamp (or lamps) EL1. In parallel with the contacts of the switch, you need to connect the indication circuit R1VD1HL1. Resistor R1 limits the current through the LED within 2 ... 3 mA, which allows you to simultaneously reduce the power released on the resistor, and hence its heating. But despite this current, the glow of HL1 is clearly visible at night, especially if an LED with a high light output is used. Diode VD1 protects the LED from reverse voltage
When the contacts of the switch SA1 are open (the light is off), the current from the network passes through the filament of the lamp and the display elements. The LED is on. When the switch contacts are closed, the lamp lights up and the LED goes out.
As HL1, you can use any LED, both domestic and imported, with any glow color. The desired brightness of its glow is set by selecting the resistor R1. Diode - any low-power, for example, series KD503, KD521, KD522
The LED is inserted into a hole drilled in the key switch housing, and the rest of the parts are placed inside the mounting box. Of course, the refinement, as well as the replacement of the resistor in the process of its selection, should be carried out with the mains voltage disconnected from the switch.
Author: I.Potachin, Fokino, Bryansk region
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