SOUND_CONTROLLED_LAMP

Published:2009/7/13 4:12:00 Author:May | From:SeekIC

Zero-voltage switching achieves interference-free proportional control of lamp intensity by sound source. Both inputs to AND gate IC15 must be high for triac to tum on. 0ne input is from zero-crossing detector IC1, Tr1,. and IC2, which produces 100-Hz series of positive-going pulses.Other input is provided by filterirectifier/com-parator circuit, Inverting input of comparator IC14, is fed by DAC IC14 which produces stepped ramp waveform from outputs of 7490 counter IC3. Counter is connected to count to 5 before resetting internally, giving five possible brightness levels for lamp. Opamps IC5, and IC6, detect when audio input falls below about 10 mV and then release IC7-IC9, from reset stage so the two 4-bit counters start counting 100-Hz waveform.Resetting occurs again when audio input next passes 10-mV level. Lamp automatcaUy turns on when music stops. All ICs are 741 or equivalent except as marked. Unmarked diodes are 1N4148, C1, and C2 are 100-nF polyester electrolytics, and all transistors are general-purpose types. Resistor values in table are for threechannel system,but more channels can be used if desired.-A. R. Ward, Sound-to Light Unit, Wireless World, July 1978, p 75.



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