Variable beeper circuit?

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Jon
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Variable beeper circuit?

I've been asked by a friend for help on some projects. One involves building a simple beeper circuit, but I'm having trouble filtering a bunch of Google crud, and I really don't know specifically where to look for simple general circuits. What I'm in need of is something that is cheap and simple to build and can produce sound at a variable rate, say from once every couple second to once every 20-30 seconds. I've thought it should be easy to make something from a 555 timer, but I have little hardware design skills. I know that something could be built using a few resisters and a capacitor. Beep timing would probably be waiting for the cap to charge, then emitting a sound from a piezo or something as it discharges. Anyone know of a circuit I could use, or have more design tips? Cheap simple and rugged are the top criteria.

The two uses it would have would be to help training of search and rescue teams for "stop and listen" skills, so that they wouldn't rely on their search dogs as much, and also use on high altitude balloons for recovery.

I'm perfectly willing to share credit for ideas, as I only told him I had a few places to check online for circuit and ideas. AF being one of them, of course. Wink

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It's a start...

you can modify this.
you might be able to replace the oscillator to a different frequency in order to make the correct beeping that you need.

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I've made that exact thing- a while ago

Jon,
You could use a 556 timer (dual timer in a single DIP package), where one timer is the "delay", and one timer the audio pulse. The reset pin of the audio timer is connected to the output of the delay timer. I have built something just like you needed several years ago, just at a much higher frequency. The circuit would make a series of high frequency bursts- my attempt to mimic a control pulse for a piece of equipment. Anyway, here's a link to a circuit that should work:

http://www.circuit-innovations.co.uk/555.html

look at the bottom of the page.

If you put pots on the two resistors on each timer block you can control the on and off times. The caps from pin 6 and pin 8 (on the 556) get you in a general range of values. The values listed are actually pretty good starts. Using higher capacitance values in the delay timer, like 33 or 47 uF, will give you a minute or two of off time, if memory serves.

give that a whirl.

mike

Jon
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Those are both great tips! T

Those are both great tips! The ThinkGeek device would be a good use for the search and rescue team, and the 566 circuit at the end of the page from the second tip would be great for the balloon recovery beeper.

Thanks!

I did more digging last night but I couldn't filter out much from all the amps and transformer and filter circuits that kept showing up.

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