mains LED

85 mains LED The very long life span of LEDs make them emi- Howev r, theira nently suitable for on/off indicatnors. ctedesince use on mains voltages has bee restri prevents their direct con- low operating voltage p l in the manner of nection with the mains suppy a neon. around this problem, the Fortunately, there is a way AC resistance of a capacitor can be used to limit the current. No power is lost in the capacitor at all, since the current passing through the capacitor and the voltage across it are 90" out of phase with respect to each other. This was described in circuit number 19 of the Elektor Summer Circuits 1979 issue. Unfortunately, that particular circuit did not work very well as the author (and our design staff) did not foresee the problem involved in switching it on!! This could have been remedied by including 100 470n (400V) 2V7 1W 81503 a zener diode in the circuit. Zener diode D2, acting as an ordinary forward biased diode in this instance, prevents excess voltage ...