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Weekend Project: Evasive Beeping Thing

Annoy your friends or co-workers with this high-tech practical joke.
Thanks go to Brad Graham and Kathy McGowan for the original article in MAKE, Volume 14.
To download
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Check out the complete Evasive Beeping Thing article in MAKE, Volume 14 and you
can see that in our Digital Edition.

Here is a link for the corrected schematic.
Use it rather than the schematic in the PDF or article.

8 thoughts on “Weekend Project: Evasive Beeping Thing

  1. Chris says:

    So, I’ve built the new circuit diagram (Thanks for that! The old one would always short out.) and the circuit is doing … nothing.
    The chips and transistors are still okay. The battery is a new 9V. Everything works… Except I cant hear anything.

    I’ve already built a circuit board for it so it’s not like I can change the circuit that much.
    Any tips will help.

    FYI I’m only 12…

    1. vivi says:

      I haven’t built this circuit but I’ll try to help.

      First, the oscillations are quite slow, so you might need to wait some time before the circuit starts emitting sound. About 70 seconds with the values from the schematic. You can attach an LED+resistor between pin 3 of the 555 and ground to check if this part operates correctly.

      Then, if the first part works, remove the 555 and attach the transistors emitters (which were connected to pin 3 of the NE555) to ground. You should hear a high pitched sound. If not, check this part of the circuit. You might also be generating a too high pitched tone to be audible. To check for this, temporarily attach 2 0.1uF capacitors in parallel with C2 and C3. If you hear a tone, this means C2 and C3 are too small and should be replaced by higher values.

      I hope this helps.

      1. Colin says:

        I originally used two 0.1uF capacitors for C2 and C3 when I built it because I didn’t have the correct parts, and it worked fine. Then when I tried 0.01uF capacitors as in the schematic I couldn’t hear anything either. So it looks like vivi’s thought is probably right that the frequency is just too high to hear.

    2. Ben says: is the correct diagram, in the pdf it shows the 9v shorted, between the -side of C1 and the speaker… clipping this wire should fix the problem but be sure the +9v still goes to to the speaker.

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