Hi there I'm looking for some help...I built the circuit and working fine however what I would like to do is once led 2 is no longer illuminated the water has drained below P2 to activate the buzzer from that point.

Cheers

 

Another inverter connected to pin 11 to will drive a buzzer connected to +V.

 

Any idea for the inverter components to implement with this ?.

Cheers

 

Just connect the buzzer + to pin 11 and ground, so that when the led goes out the buzzer sounds.

 

Could you abandon P1 and use inverter 7 in a new role to operate the buzzer?

 

Alec T that was my first consideration but the way I have it laid out on the board I will use all the inputs for this application....at point 2 is where I need the buzzer to activate at a later date I may change that though.

 

Use a ULN2805 has 8 gates, take the output of P2 to the spare inverter and the output to the buzzer P7.
Max.

 

MaxHeadRoom yes that's the IC I should have used but it's made up now and I bought 20 on fleabay so I'm sort of in a jam lol...cheers

 

Dodgydave when the led is on so is the buzzer.

 

You can try the circuit as below, I'm not sure about the current of Buz, if the current less then 33mA then you can using 2N3904, if the current more then 33mA, then you should pick up the bjt for some more current.

 

ScottWang Thats exactly what I was thinking of but not the experience to solve....and this will work when the LED 2 turns off....Thank you very much appreciated....cheers