A possible problem is that my circuit draws 9.7mA continuously from a 6V supply. 17mA in alarm. Though not a great deal of current, if this is to be left unattended for long periods of time, a battery might run down and leave you with no alarm.

However, I just just checked the circuit with reduced voltage and no water present, it goes into continuous alarm (no pulsing) at ~3.5V. Current draw is then ~13mA. I'm using a SONALERT tone buzzer rated at 1-5VDC, which will work at that low a voltage.

Can you explain how and where you intend to use you circuit?

Ken

 

Can you explain how and where you intend to use you circuit?

Ken

I'm gonna use this for the water tank on the terrace. May be I'll use 9V battery. Can you try with 9V.

 

Are talking about a PP3 rectangular 9V battery? The alkaline ones only have about 550mAh capacity. With my circuit drawing ~10mA continuously, it might last over a week. 4 AA alkaline batteries @ 6V will last 3-4 months, maybe more. There in no advantage in using a battery with a higher voltage and less mAh capacity in my circuit.

Ken

 

I have a question what/how are the sensors constructed? I am looking into making a flood alarm for my basement but my big stumbling block seens to be the sensors?

 

I have a question what/how are the sensors constructed? I am looking into making a flood alarm for my basement but my big stumbling block seens to be the sensors?

I always use stainless steel TIG welding rod...because it doesn't corrode... and I have it . You could use cheaper stainless steel wire from the hardware store. Sensor configuration is generally two conductors that both touch the water's surface at about the same time. A lot depends on where you're anticipating a flood. Top of a sump?...on the floor near a washing machine?...window wells?

Ken

 

As an experiment, I changed R1=100K, R2=1M, and C1=1.0uF and brought the quiescent current down to ~4mA.

My guess is that a circuit using something like a CD4093 might have an even lower quiescent current......Like this:http://www.extremecircuits.net/2010/04/water-alarm-circuit-diagram.html

Ken

 

Are talking about a PP3 rectangular 9V battery? The alkaline ones only have about 550mAh capacity. With my circuit drawing ~10mA continuously, it might last over a week. 4 AA alkaline batteries @ 6V will last 3-4 months, maybe more. There in no advantage in using a battery with a higher voltage and less mAh capacity in my circuit.

Ken

Thanks buddy. But I'm using manual switch to turn on/off the circuit so I guess quiescent current will not be an issue.

 

So now I've build this circuit and it is not working!
It doesn't mean the circuit is wrong or my soldering skills are questionable
Actually it's not working in the water tank for which I intend to use it.
My first guess was conductivity of that water. Did little experiment! Added some salt (Na-Cl) to the sample of that water. And guess what?? It works so my guess was right! CONDUCTIVITY!!.
Now I feel I need to work around another method. Because I can't add tons of salt in the water tank just to make one simple circuit work.
So any different ideas??? I've read some people using IR or something?? How exactly? And any other options????

 

Do you have a multimeter? Can you measure the resistance of the water (no NaCl)? Just touch the probes to the water ~1cm apart?.

Ken

 

Do you have a multimeter? Can you measure the resistance of the water (no NaCl)? Just touch the probes to the water ~1cm apart?.

Ken

Of course I've. The resistance is >1MΩ. Tried for 30sec or so...It goes on increasing..Now??

 

Well at this point I would just go with a battery, buzzer, and a float switch.

Ken

 

Okay. Float switch hmm. Is there any other way. Which I can manage at home(with available stuff)

 

I have no idea what stuff you may have available.
You can make a float switch.
GoogleIY float switch
Lots of examples.
An advantage of the float switch/battery/buzzer alarm is that it only draws current when in alarm.

Ken

 

I have no idea what stuff you may have available.
You can make a float switch.
Ken

General electronic stuff buddy! Resistors, transistors, capacitors etc.
So how can I make my own float switch?

 

Sorry about: Google: DIY float switch (smiley face)
It should have been: Google: DIY float switch homemade

Ken

 

Yeah. I'll try. Will get back when done!

 

A coat anger with a cork on one end and a loop, to act as a hinge, on the other. A leaf-arm "microswitch", with leaf resting against the wire. When the float rises with the water, the wire pushes up against the switch arm, closes the switch contacts, and sets off the alarm. Or a ping-pong ball in a short section of PVC pipe. The switch arm sticking through the side of the pipe. when the ball rises with the water, it pushes up on the switch arm, and....

Ken

 

A coat anger with a cork on one end and a loop, to act as a hinge, on the other. A leaf-arm "microswitch", with leaf resting against the wire. When the float rises with the water, the wire pushes up against the switch arm, closes the switch contacts, and sets off the alarm. Or a ping-pong ball in a short section of PVC pipe. The switch arm sticking through the side of the pipe. when the ball rises with the water, it pushes up on the switch arm, and....

Ken

Ohh! Can you post some images? May be painted in paint

 

ALL contact water level sensing circuits eventually fail. I know from experience. The most reliable level sensing circuits today are non-contact ultrasonic ones.

Cheers, DPW [Everything has limitations...and I hate limitations].

 

http://reefworkshop.com/DIY_floatswitch1.htm This is the cork on the end of a coat-hanger concept.
http://www.otherpower.com/float_switch.html I would replace the pill bottle float/magnet with a ping-pong ball and the reed switch with a long arm microswitch http://www.mcmelectronics.com/content/productimages/s4/3926944.jpg

Ken