|
Detects 1.8 to 220 Volts DC or AC - Minimum parts counting
Parts:
D1 - 5 or 3mm. Red LED
D2 - 5 or 3mm. Green or yellow LED
LP1 - 220V 6W Filament lamp bulb
P1 - Red probe
P2 - Black probe
Device purpose:
This circuit is not a novelty, but it proved so useful, simple and cheap that it's worth building. When the positive (Red) probe is connected to a DC positive voltage and the Black probe to the negative, the Red LED will illuminate. Reversing polarities the Green LED will illuminate. Connecting the probes to an AC source both LEDs will go on. The bulb limits the LEDs current to 40mA @ 220V AC and its filament starts illuminating from approx. 30V, shining more brightly as voltage increases. Therefore, due to the bulb filament behaviour, any voltage in the 1.8 to 220 Volts range can be detected without changing component values.
Note: A two colors LED (Red and Green) can be used in place of D1 & D2.
|
