sound activated 555 timer circuit????

hi,
one of my pupils wants to make a circuit that will be activated by sound(such as a clap). we use 555, comparator op-amps counters etc,(15 year olds class). we do not know what component to use to trigger the control circuit???
any ideas for us please?
much appreciated, jd

An electret microphone (part number 252-em9745p-40 from Mouser, 95 cents), plus an op amp to raise the signal enuf to trigger the 555. You can get the data sheet from mouser (www.mouser.com) which includes a suggested circuit. You will need to experiment with gain and capacitor value so a clap will trigger the 555 but ordinary converstion will not.

clap switch



you have to use a high pass filter connected to the op-amp so it wont trigger with just any sound, that way you can activate it by snapping a finger or by clapping. as an added suggestion you can use CD4013 a dual flip/flop to trigger the 555 :lol: