# Single tone buzzer with 555 timer

Discussion in 'Homework Help' started by PsySc0rpi0n, Oct 24, 2015.

1. ### PsySc0rpi0n Thread Starter Well-Known Member

Mar 4, 2014
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Ok, my final problem to solve is to project a single tone buzzer with 555 timer!

I have found a schematic and I'm using it. The problem here is that I don't know how to simulate the buzzer. Can I do it with a small resistor?

This is the circuit I'm using without the switch SW1:

I tried to replace the BZ1 with a small resistor but I can't see any pulse going on. I don't know if I can replace the buzzer with a resistor. This is supposed to be a monostable mode 555 timer generating a single tone buzz.

Any help on this one?

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Last edited: Oct 24, 2015
2. ### #12 Expert

Nov 30, 2010
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I can't see an .asc file but maybe the problem is that a monostable circuit doesn't oscillate.

3. ### PsySc0rpi0n Thread Starter Well-Known Member

Mar 4, 2014
1,184
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Can you see the picture? The .asc file is attached as usual???

And for this example, it is supposed to generate a single tone buzz... So, I think it doesn't need to oscillate!

4. ### WBahn Moderator

Mar 31, 2012
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A "tone" and a "buzz" both imply an oscillating signal.

A "single tone" would seem to imply a circuit whose frequency of oscillation is constant.

If you use a monostable, it would seem that, at best, you would get a "chirp".

Where is the notion that you need to use a monostable coming from?

5. ### #12 Expert

Nov 30, 2010
16,261
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So what's the problem? A buzzer buzzes if you give it some DC current. You ask about not seeing any pulses on the output of a DC switch. What's the problem?

6. ### GopherT AAC Fanatic!

Nov 23, 2012
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Get rid if R1 and C1.

Connect Pin 2 to Pin 6

Add a 1k resistor between pin 6 and 7 instead of the plain wire

Move the speaker between the transistor's collector and ground (put a plain wire to connect Vcc to transistor's emitter)

Change your timing resistor on pin 6 to 0.1 uF
Change the 120k timing resistor to 10k

Last edited: Oct 24, 2015
7. ### JoeJester AAC Fanatic!

Apr 26, 2005
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If The symbol (speaker) is a speaker, the 555 must oscillate at some annoying frequency.

If that symbol is a buzzer or sonalert, the 555 needs to pulse at a low frequency to produce a more annoying sound.

8. ### WBahn Moderator

Mar 31, 2012
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Good point -- I'm thinking in terms of driving a speaker and not a piezo buzzer module or something similar. If it's a buzzer module, than a monostable would make it buzz while the output of the 555 is LO.

Psy: Are you taking into account the inverting nature of the transistor?

9. ### PsySc0rpi0n Thread Starter Well-Known Member

Mar 4, 2014
1,184
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What you mean change my timing resistor on pin 6 to 1uF??? A resistor with Farads? You just told me to place a resistor between pin 6 and 7 (haven't told any value for this resistor).

Can you be more clear, please?

10. ### PsySc0rpi0n Thread Starter Well-Known Member

Mar 4, 2014
1,184
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For this one is just a buzz...

As I said to JoeJester, for now it's just a constant single buzz, sound, whistle, whatever we can call it! And of any duration!

11. ### WBahn Moderator

Mar 31, 2012
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Do you physically have the buzzer?

If so, connect it to a 9V battery and measure the current flowing in it. That will tell you the value of resistance that is reasonable to use for it.

12. ### JoeJester AAC Fanatic!

Apr 26, 2005
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So, you want a monostable. And you will need to measure the voltage drop across the resistor simulating the buzzer or view the current thru that resistor.

13. ### #12 Expert

Nov 30, 2010
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A, "just in case" post. I was looking at a drawing with a part labeled, "BZ1".
Right or wrong, that tells me it buzzes by itself if you just give it some current, and thus my conclusion.

14. ### WBahn Moderator

Mar 31, 2012
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A very good chance you are correct.

I don't play with these parts too much myself any more and when I did it was a buzzer module. But I've got some friends that do a lot of work driving piezo elements directly (not a buzzer, just the raw element) and they always refer to them as "buzzers", hence my bias toward always thinking of a "buzzer" as a raw element.

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15. ### PsySc0rpi0n Thread Starter Well-Known Member

Mar 4, 2014
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No no... I'm just trying to run a simulation...

Ok, this is the pre-lab theoretical part of my assignment. So at this point, we are only supposed to work with LTSpice. So, no hardware for now!

And for this problem, teacher is just asking us to project a circuit that makes a siren to emit a single tone noise! Then we have to project another that makes a so called "american siren" which I suppose to be a dual tone siren or so!
At this point I'm not even sure if we are going to use a single buzzer or a piezzo something that you talked about somewhere!

16. ### #12 Expert

Nov 30, 2010
16,261
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Ah, semantics. A poster called Pedro just mentioned that he was having difficulty keeping up with the way different people describe the same thing. Speaker, piezo element, buzzer...very similar things and sometimes loosely used words.

It comes with the territory. There are so many people here from different countries, schools, specialties, and decades that overlap and confusion is inevitable. That is merely a good reason why I call Threads, "conversations". It has to be a two way conversation or Threads would go off-topic constantly.

17. ### JoeJester AAC Fanatic!

Apr 26, 2005
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You could go either way, an astable with a speaker (single tone) or monostable if you have a real buzzer.

Did you get a list of components for the lab?

18. ### PsySc0rpi0n Thread Starter Well-Known Member

Mar 4, 2014
1,184
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Yes... We have a list of components but curiously teacher probably forgot to mention this component. The list has no buzzer or piezzo or speaker at all listed!

So, can I use the circuit that is in my 1st post to try to see it working?

19. ### GopherT AAC Fanatic!

Nov 23, 2012
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You can but I am not sure it meets the intention of the teacher's assignment. It is my guess that the teacher wants the 555 to generate an audible tone (astable mode). If you use a buzzer instead, like you have so far, what is the point of the 555.

Think about it, your interpretation is better titled, "self-turning off buzzer" than your title on this thread, "single tone buzzer with 555 timer".

20. ### JoeJester AAC Fanatic!

Apr 26, 2005
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Is your project is to emit a single continuous annoying tone?

Your ears with thank you for that switch.