Best choice for detecting water?

[mackrackit]

Personally I have had god luck detecting a high water level with the digital IO method.
I have the PIC pin pulled low and apply a positive voltage to the probe. No current is used untill the water makes contact. When contact happens you will want to turn the power off to the probe to save power and to cut down on oxidation on the probe.

You can use a timer off of the PIC to periodically turn the power on to the probes and check for conductivity.

What kind of water is this? Potable, seawater, sewer? Decide what to use for the probe material? If it is sewer watch for sparks

[ShortBus]

Thanks for the reply. It's just ordinary tap water; no worries about explosions. ;-)

I was hoping that the simple solution would work. Can you explain your circuit a bit more? Are you using a resistor between the i/o pin and ground? If so, what value?

[mackrackit]

I apologize. I failed to mention the LM339 comparator driving the PIC IO.
It is still a simple solution. I built the one for my water system back in my basic stamp days. Still working.

Again I am sorry for the misleading post.

[ShortBus]

No problem. I don't imagine that you have a schematic of your circuit? Could it be adapted to use the integrated comparator onboard the pic?

[aratti]

All I want to do is create a sensor that beeps when water bridges a pair of contacts

You could use a simple floating switch. See an example @

http://www.homesecuritystore.com/p-8...mac=4&zmap=SB2

Al.

[ardhuru]

I was looking for something similar a few weeks back, except my requirement was more complex as I wanted to detect 10 different levels of water using a simple 2 wire probe.

Anyway, while I cant pretend to have found the perfect solution, Arrati's suggestion in that thread (http://www.picbasic.co.uk/forum/showthread.php?t=11468) came pretty close.

So, my vote would be stainless steel nut-bolts to make the actual contact, with a good resin epoxy sealant around the wire connected to the bolt. This coupled with a software arrangement to drive the sensor with a duty cycle of perhaps 1:10, or even 1:100 would give you years of maintenance-free use.

Incidentally, I used the adc of the pic, rather than the comparator, although in your case the comparator (or even a digital input) should be fine.

Regards,

Anand Dhuru

[ShortBus]

Arrati, thanks for the idea, but I'll need an electrical solution rather than mechanical in this application.

Anand, any chance you could post an example circuit?