Circuit knowledge

This schema is simple, but very useful as well as simple and inexpensive. Its use is simple, when the positive (red) is connected to a positive voltage DC and the black lead on the negative, the red LED lights. Reversing polarities the Green LED lights. Connecting the ends to an AC source both LEDs will light. The lamp current is limited to 40mA LEDs @ 220V AC and its filament is illuminated with approximately 30V, shining more intensely with increasing tension. Therefore, due to the behavior of the filament, any voltage in the range of 1.8 to 230 can be detected without changing component values​​.

Suitable AC DC Circuit Diagram




D1 = 3 mm or 5. red LED
D2 = 3 mm or 5. green LED
LP = 1220V 6W NEON