Connecting a 8 ohm buzzer to a 555 timer : help !

[audioguru]

thank you ! where in the circuit should i plug the rain detector and the led ?

The circuit you copied comes from India where the rain might be acid (have you seen their smog polluted air?). Acid rain conducts but the rain where you are might be pure water that does not conduct. So plug the rain detector in India.

The sound with the series resistor is very weak because the resistor limits current from the 555 so that the 555 is not overloaded.

The 555 and the speaker can be replaced by a piezo beeper (with an oscillator in it) and could be turned on and off with a transistor.

 

[laurencelovesphysics]

okay this is perfect thank you. why don't i need the capacitor anymore? only some R?

 

[danadak]

No less than 50 ohms.

Regards, Dana.

 

[audioguru]

A speaker works best when its coil is in the center of the magnetic field. Without a coupling capacitor blocking the DC from the 555 then the speaker works poorly on one side of the magnetic field or the coil smashes into the magnet structure on each cycle. With a capacitor blocking the DC then the speaker works properly.

But this project has only a tiny amount of output power which might cause no problems with DC in a high power speaker.

 

[laurencelovesphysics]

update: i now have a buzzer, but no current is coming out of the output of the 555 timer and it is a new one so im sure its not burned

 

[danadak]

With the speaker disconnected do you see, with oscilloscope, waveform on
output pin ? If no scope use a pair of headphones and a 1K resistor in series
to output to see if 555 is running.

So how did you connect speaker to 555 ? Components used and values....

Regards, Dana.

 

[audioguru]

The original circuit was designed to drive a speaker (transducer) with AC, not a buzzer with DC.
You did not say if the new buzzer is electro-mechanical or piezo. You did not say what is its very important voltage and current ratings.
The original circuit was designed to be activated with water that is conductive with some salts in it, did you try shorting its rain sensor?

 

[audioguru]

A moment ago I saw the other forum about this rain detector and copied the photo of its piezo transducer that is not a buzzer and is not a piezo beeper that has an oscillator in it:

 

[laurencelovesphysics]

it is a buzzer like this

 

[laurencelovesphysics]

With the speaker disconnected do you see, with oscilloscope, waveform on
output pin ? If no scope use a pair of headphones and a 1K resistor in series
to output to see if 555 is running.

So how did you connect speaker to 555 ? Components used and values....

Regards, Dana.

honestly i don't know how to connect it, I'm looking at circuits online put nothing concluant so far. I know how to connect it so that the buzzer buzzes but it always buzzes, not only when the there is rain on the sensor

 

[laurencelovesphysics]

The original circuit was designed to drive a speaker (transducer) with AC, not a buzzer with DC.
You did not say if the new buzzer is electro-mechanical or piezo. You did not say what is its very important voltage and current ratings.
The original circuit was designed to be activated with water that is conductive with some salts in it, did you try shorting its rain sensor?

the rain sensor works fine, salt or no salt. I honeslty dont know what type of buzzer it is there is nothing written on it and a friend bought it for me

 

[audioguru]

As a test, connect the piezo beeping thing to a 9V battery with the red wire as positive and the black wire as negative. If it continuously beeps then it has an oscillator inside and is not the "transducer" that is needed.

The completely wrong circuit from India has a capacitor C4 in series with a wrong kind of speaker. If your beeper has an oscillator in it then it will not continuously beep if the capacitor is the correct way around but will beeeeep if the capacitor is backwards. The correct kind of piezo transducer does not need a capacitor C4 in series with it. The 555 is the oscillator that drives it.

 

[laurencelovesphysics]

when i only plug the buzzer, it beeps continuously, the thing is when i plug it in the timer with or without the capacitor, it doesn't beep. If i connect the timer as basic as it is with the buzzer, it beeps but its not beeping according to the rain detector

 

[audioguru]

A piezo transducer is needed for the rain detector circuit. The 555 is the oscillator that makes it beep. A transducer makes only a click when connected to a 9V battery, not a beep.
Your piezo is a beeper that has an oscillator in it, your beeper is the wrong kind that is supposed to be a transducer.

 

[laurencelovesphysics]

okay i will buy that thank you

 

[audioguru]

Take a 9V battery to the store because a piezo beeper and a piezo transducer look the same.

 

[laurencelovesphysics]

okay and if a have the right buzzer, the circuit from india should work or still no ?

 

[audioguru]

The circuit might work with the correct piezo transducer and acid rain in India.