LED 'amplifier'

LED "amplifier" The light emission of an LED is normally pretty low. If more brightness is required, the following circuit will help. The LED to be "amplified" is replaced by an LED in an opto-coupler which switches a lamp (for instance, a signal lamp) connected to the mains supply. When the LED in the opto-coupler lights, the photo transistor con- ducts. This causes a gate current to flow to the triac via R1: the triac fires and the lamp lights. Resistor R1 is connected to 30 VDC which is derived from the mains supply 2—4 IC7 BC TIL 111 5476 R4 BC 547B 22 D2 2, 15 V 1W C1 r La 1 15...100W D3 1N4004 _Dl. R4 2W R2 15 ■1004 ~ I R3 40V BC R5C L J T1 T3 5576 Tn 1 ° ° 1W loon via Dl and R4. Two zener diodes, D2 and D3, limit the voltage across buffer capacitor Cl to 30 V. The three transistors T1 ... T3 ensure that the triac can only be fired at the moment the mains supply changes from positive to negative, thus reducing interference problems. When the voltage in the positive hal...