DIY Clapper

[Patrick's] latest Instructable walks us though making a clap clap on / clap clap off type of switching circuit, similar in use to that sometimes popular commercial product seen on TV. He does this by using a standard electret microphone, half of an LM324 op amp, a voltage comparator and a PIC micro controller.

The operation of the device is as simple as its wiring, the microphone picks up sound and produces a signal, that signal is stripped of its DC component and fed into the op amp, after 2 stages of amplification the signal passes though a voltage comparator, and if the sound was loud enough a timer is triggered on the pic. Two claps within the specified amount of time, the micro then switches on a relay which can toggle your outside appliance (keeping the load in mind).

On the last page [Patrick] also gives a rough outline of how to make a single clap on / off variant using a 555 timer and some flip flops. Join us for a quick video after the break, and be sure to check this one out.

Comments

  1. swighton says:

    Isn’t the clapper used to switch 120VAC lights/tvs and such? This looks like it can only handle 5V.

  2. Jonathan says:

    @swighton
    “””the micro then switches on a relay which can toggle your outside appliance”””

    You could also easily make a double clap with a 555 also… just use a 555 monovibrator triggered on the falling edge of the clap signal to define the valid length after a clap, then AND it with the clap signal.

  3. Jonathan says:

    That said, the PIC would allow for more complex clap patterns, even reprogrammable ones!
    Nice useful circuit for PIC beginners to try out :)

  4. Jeff says:

    My son and I made something almost exactly like this for an “invention fair” last year. His idea was to turn a light switch on when his alarm went off, but in the end, we realized that we’d just re-invented the clapper. Jonathan is right — the double clap can be achieved without a microprocessor. Our needs were simpler — one audio trigger, but a delay before another signal was allowed in. So, dual 555 chips (single 556 really), and some logic gates. Not 555 contest-worthy, but fun nonetheless.
    This week’s project(almost a year later) is moving it to a PCB. It’s funny how similar it looks to the picture above.

  5. swighton says:

    @Jonathan
    I saw the relay, and that it was 5V which I retardedly was thinking was the voltage handling capability of the relay, not the coil rating. I don’t know where my mind was…

  6. jamieriddles says:

    “that signal is stripped of its DC component”

    forgive me if I’m wrong but isnt the signal stripped of its AC component?

  7. jim says:

    So you’re watching some crappy show on TV and the clapping starts in 7.1 surround and oooh shit the wiring is on fire.

  8. strider_mt2k says:

    Can this one also be falsed by flipping a nearby light switch on and off?

  9. Jonathan says:

    @jamieriddles
    Nope, the microphone overlays an AC signal (voice, noise, claps, etc) on the DC ‘bias’ voltage used to power it.

    The AC is what we’re interested in :)

    @strider_mt2k
    not unless it’s very close, a very loud switch, or the threshold is too low…

  10. sanjvwin says:

    Hello,
    Can this circuit work for an electric bulb(ac)
    please send me the circuit for electric bulb clap clap on and clap clap off switch

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