Water sensor circuit modification

[cannibal]

Hello

could you please show me how I can connect the buzzer instead of relay in the following circuit

because when I changed it to buzzer then it's just wont stop making noise

**broken link removed**

 

[audioguru]

You forgot to add a protection diode so I think one or both transistors are blown up.

The reay generates a few hundred volts when it is turned off. A reverse-connected diode is needed to arrest the high voltage like this:

 

[cannibal]

you are right

but how can I make a connections to test this semple circuit without relay

I mean the output will be directly buzzer

 

[audioguru]

If the buzzer is a mechanical one then it will also generate a high voltage like the relay and blow up more transistors if the circuit doesn't have a protection diode..

 

[mynameisdan]

Remove q1 and the relay. Then put your buzzer in place of R1. Where Q2 was connected to Q2 put it to ground. Remember your protection diode too.

 

[cannibal]

Like this ??

 

[audioguru]

Your diode is across the battery. The battery doesn't generate a high voltage, the mechanical buzzer does. Connect the diode across the buzzer.

The single transistor won't have enough sensitivity to detect water unless the water is very salty. Use the original two transistors and just replace the relay with the buzzer and include the diode across the buzzer if it is a mechanical one.
If the buzzer is a piezo beeper then the diode is not needed.

 

[cannibal]

I have done like this before and the buzzer won't stop making noise even if the probes are outside the water

 

[audioguru]

I have done like this before and the buzzer won't stop making noise even if the probes are outside the water

Then one or both of your transistors are either wired wrong (look at the picture of their pins on their datasheets) or they are burned out.

A transistor is turned on with base current. With nothing between the probes then the 1st transistor doesn't have base current and is turned off. Then the 2nd transistor is also off. Then the buzzer is also off.

 

[Gordz]

Put a 100k resistor from the base of Q2 to ground, and then try it.