Small circuit to run a LED on line voltage (English)
This little circuit allows to connect a LED to line voltage. A LED can not handle with 230V AC and needs a current which is limted to ca. 15mA. The first issue is simply solved with a diode which eliminates the voltage in reverse-biasing. The current is limited by the combination of the resistor and capacitor. Used at AC capacitors work as frequency dependent resistors. You can simply calculate the capacitive resistance of the capacitor by the following formula:
Based on a frequency of 50Hz and a capacity of 220nF you get a reactance of ca. 16kΩ. This is just perfect for a LED. The resistor prevents that the capacitor does not charge that abruptly.
Hinweis
Attention. This circuit works with life threatening line voltage. All parts of this circuit are connected to the grid! You have to make sure that it is not possible to touch any parts of the circuit at any time. You have to unplug the circuit everytime you want to check it.Part list
- C1: foil capacitor 220nF, 250V~ (stick to the values!)
- R1: 2,2kΩ
- R2: 220Ω
- D1: 1N4007 (or comparable; must be suitable for 220V/230V)
- LED1: standard LED
Circuit diagram
