jbelectric777

I have been "dabbling" with caps and resistance with the 555 timer and what I am trying to do is to get a small speaker to oscillate fast enough for the sound to be super high and then even almost silent. I got the idea from someones dog whistle a while back. Now i know how to make the 555 go from slow to fast using an adjustable pot but when the resistance gets too low it seems like the IC becomes saturated and doesnt oscillate anymore, the load (in this case i was using a piezo buzzer) just stayed on. So if you guys and gals can tell me how the 555 works then the schematic will be more understanding to me, I know the very basics but I cant move on till I know not only how to hook it up but why we hook it up that way. And also note, I must have butted in on someones thread a little while back, sorry about that, I havent been on in a while and I forgot how to start a new thread, I think I have it right this time. Thanks in advance, Jim

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Brian218

Here are a couple of links to 555 tutorials

http://www.uoguelph.ca/~antoon/gadgets/555/555.html
http://www.elektropage.com/555timer/

This is an online calculator for the 555.
http://ourworld.compuserve.com/homep...Bowden/555.htm

audioguru

When you reduce the value of a pot, its resistance becomes too low for the circuit and the circuit stops working.
The frequency of a 555 is also controlled by its timing capacitor's value. When the capacitor's value is smalled then the frequency is higher.

Many speakers do not produce very high frequencies. A tweeter can but it is freagile and a continuous tone might damage it.

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Hero999

I wouldn't think the 3V peak squarewave provided by a 555 running from a 9V battery can damage a tweeter.

You can calculate the capacitor and resistor values, using the formulae provided on the datasheet which can be found using Google.

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audioguru

Hi Hero,
I have seen tweeters that are just a photo of a tweeter.
Some little tweeters are damaged by a 1W continuous tones.
With a brand new 9V battery a 555 will try to produce an output power of 1W into an 8 ohm tweeter. I don't know which will fry first, the battery, the 555 or the tweeter.

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