Siren circuit

[krahnerl]

Hello members I am a basic beginner in hobby electronics. I built a ' siren circuit ' ( short circuits project ) and the sound from the 8 ohm speaker is very soft. I replaced the 100 ohm resistor with 3 x 10 ohm resistors ( a slight improvement then I replaced a 10K ohm resistor with a 6K8 ohm resistor. Louder noise. My question. Can I damage the speaker, the transistors or the capacitor ? Thank you

 

[danadak]

Post a schematic so we can give you more complete and accurate advice.


Regards, Dana.

 

[Delta Prime]

I built a ' siren circuit ' ( short circuits project )

Your short circuit project is about to become very successful congratulations. (Just kidding)
If you built the circuit can I take a peek.

the sound from the 8 ohm speaker is very soft. I replaced the 100 ohm resistor with 3 x 10 ohm resistors ( a slight improvement then I replaced a 10K ohm resistor with a 6K8 ohm resistor. Louder noise

So let me get this straight you are adding discrete resistors onto an eight ohm speaker,correct?

 

[AnalogKid]

Paraphrasing Rear Admiral Joshua Painter,

"Engineers don't take a dump, son, without a schematic."

 

[krahnerl]

Post a schematic so we can give you more complete and accurate advice.


Regards, Dana.

Thank you. Enclosed is an image. Regards Les

 

[krahnerl]

Your short circuit project is about to become very successful congratulations. (Just kidding)
If you built the circuit can I take a peek.

So let me get this straight you are adding discrete resistors onto an eight ohm speaker,correct?

Hi Delta Prime I am enclosing an image showing 3 x replaced resistors and schematic. Thanks

 

[bertus]

Hello,

From wich book does the circuit come?
Lowering the 10K to 6k8 will change the tone.
Lowering the 100 Ohms to 3X10 Ohms will have a higher output, but may stess the transistors.

Bertus

 

[Ylli]

Note that anything you do to make it louder will increse the stress on the transistors. Don't have time now to do an anaysis... Even as you reduce the value of the 100 ohm series resistor, speaker current is still going to be limited by the 220 ohm collector resistors. Try reducing those collector resistors from 220 to 100 ohms. Then additionally reduce the value of the speaker series resistor.

 

[krahnerl]

Hello,

From wich book does the circuit come?
Lowering the 10K to 6k8 will change the tone.
Lowering the 100 Ohms to 3X10 Ohms will have a higher output, but may stess the transistors.

Bertus

Hi Bertus and YIIi Thank you. It is Vol 1. I'm rethinking with original 100 ohm and looking at 220 ohm's as well. I have done some other projects but working towards the AM radio, using a 555 instead of a MK484 ( gone missing ). Thanks again. Les

 

[davenn]

. It is Vol 1

vol1 of what ??

 

[krahnerl]

vol1 of what ??

Hello members ... Thank you davenn for your query. I have reposted my original question, and my question was answered.... please refer if you wish. I am a basic beginner in hobby electronics. I built a ' siren circuit ' - project No 8B, ( from Short Circuits Vol 1 ) and the sound from the 8 ohm speaker is very soft. I replaced the 100 ohm resistor with 3 x 10 ohm resistors ( a slight improvement then I replaced a 10K ohm resistor with a 6K8 ohm resistor. Louder noise. My question. Can I damage the speaker, the transistors or the capacitor ? Thank you

 

[Harald Kapp]

mod edit: changed the thread title so it reflects the question better.

Can I damage the speaker, the transistors or the capacitor ?

speakers: possibly, it depends on the nominal wattage these are desigend for.
transistors: possibly, as has been answered before. It depends on some conditions like rated power of the transistors, cooliong (heatsinks) etc.
capacitor: unlikely.

This "siren circuit" is a basic astable multivibrator (link) with the speaker connected across the two outputs. This is a working design, but not a good one. A better design will separate the generation of the signal from the amplification and output. To increase the volume i suggest:

1. remove the speaker and series resistor from the circuit.
2. Add an amplifier stage. Since this is a simple digital signal, you can use a single transistor stage as described in this resource.
   
   Remove D1, replace the motor by the series connection of resistors and speaker. Make R1 approx. 10 × (resistance of resistors and speaker). Connect the open end of R1 to either one of the outputs of the astable multivibrator.
   
3. Make sure the speaker is enclosed in a closed cabinet or housing. A bare speaker without enclosure will always emit at a comparatively low volume due to the acoustic short circuit between front and back of the speaker.
4. Consider using a piezo buzzer instead of the speaker. Piezo buzzers can be astonishingly loud when it comes to reproducing single tones as from a siren.
   

 

[krahnerl]

Thank you Harold and everyone for your assistance. Now I need to go back to the books and find o ut t what it all means. Regards Les