Single tone buzzer with 555 timer

Thread Starter

PsySc0rpi0n

Joined Mar 4, 2014
1,446
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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Thread Starter

PsySc0rpi0n

Joined Mar 4, 2014
1,446
I can't see an .asc file but maybe the problem is that a monostable circuit doesn't oscillate.
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!
 

WBahn

Joined Mar 31, 2012
26,055
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?
 

GopherT

Joined Nov 23, 2012
8,012
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
 
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JoeJester

Joined Apr 26, 2005
4,312
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.
 

WBahn

Joined Mar 31, 2012
26,055
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?
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?
 

Thread Starter

PsySc0rpi0n

Joined Mar 4, 2014
1,446
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
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?
 

Thread Starter

PsySc0rpi0n

Joined Mar 4, 2014
1,446
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.
For this one is just a buzz...

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?
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!
 

WBahn

Joined Mar 31, 2012
26,055
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.
 

JoeJester

Joined Apr 26, 2005
4,312
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.
 

#12

Joined Nov 30, 2010
18,210
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.
 

WBahn

Joined Mar 31, 2012
26,055
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.
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.
 

Thread Starter

PsySc0rpi0n

Joined Mar 4, 2014
1,446
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.
No no... I'm just trying to run a simulation...

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.
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!
 

#12

Joined Nov 30, 2010
18,210
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.
 

JoeJester

Joined Apr 26, 2005
4,312
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?
 

Thread Starter

PsySc0rpi0n

Joined Mar 4, 2014
1,446
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?

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?
 

GopherT

Joined Nov 23, 2012
8,012
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?
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".
 
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