knock switch

7-68 elektor july/august 1980 And now for something different ... Over the years, all kinds of wired and wonderful switches have found their way into the pages of this magazine: touch activated switches, clap switches, temperature sensitive switches, and so on. But never one like this: it switches when you knock it! (Don"t bother to write in that you already have several mechanical switches that also require a good clout now and then. We have the same problem). No real blow is needed for this one, however: a light tap is more then enough. The "knock sensor" is a common-or-garden choke coil, or a plate with the choke mounted on it. Don"t knock this idea before you think it over — we can think of any number of possible applications. For example: since modern pop music is going more and more electronic every day, this switch may prove ideal for use with an electronic drum synthesiser. It can be operated with a drumstick! So how does it work? The core of a choke is made of ferro-mag...