Best choice for detecting water?

[Charles Linquis]

About 40 years ago, I needed electrodes for electrolyzing water. All the metal ones had problems, but I found a great solution in the carbon rods that go down the middle of zinc-carbon dry cell batteries. They even have a metal cap crimped on one end that you can solder to.

If you can still find them.

[ardhuru]

You should be fine with stainless bolts as sensors, as long as you've properly insulated / epoxied the connection between them and the wire. Plus, if you can, run the pic off a 3 volts supply, the probes will last that much longer.

Regards,

Anand

[Melanie]

This device is extremely reliable (as long as it's not sewage which tends to coat the optics!) and is actually manufactured by Honeywell Microswitch in the USA. Connect with minimal components directly to your PIC (or even Relay).

http://docs-europe.electrocomponents...6b8001adaf.pdf

It is a little power-hungry for Battery applications though.

You don't have to go Stainless Steel if you use AC exitation on your probes... PWM say a 1kHz signal to one probe (via a 100nF Capacitor, the other probe (again via a 100nF) can be used to detect the signal returning. To minimise power consumption, turn the PIC on only every few seconds (typical Rain Detector application to alert you to take the washing indoors).

[Acetronics2]

Hi, Folks

This one doesn't show any Pic ... is not a " Bling-Bling" device, but works perfectly ...

Published in ... 1983 !!!

DUS means: general use Silicon diode : 1N4148, BAW62 ...

Alain

[Acetronics2]

The " Bling Bling " device :

http://a110a.free.fr/SPIP172/article.php3?id_article=29

Alain

[ErnieM]

Ive done two "water" sensors in my time. First was decades ago using a CMOS quad gate, 1 gate to detect rain, 2 to make a gated multivibrator, and 1 spare.

Theory is CMOS has near infinite input resistance, so you use a megaohm pull-up resistor on the gate input, and the probe is the input and ground signals. Any liquid bridges the input pulling it to ground. I have not tested this with a PIC, but since the PIC is CMOS based I would expect this trick to still work. Even better would be to set the input as analog and use a A2D to sense (immune to half-VDD input level disasters). A baseline 10F part should work.

The next version was a continuous level sensor similar to this: http://www.innovativesensing.com/htm...ucts.asp?id=18

The probe is a tube within a tube to form a capacitor. Changing liquid heights change the dielectric which changes the capacitance linearly with level height. My "boss" used a 555 timer to convert the capacitance to a frequency, I used a PIC to measure the frequency, calibrate the levels for whatever fluid was being used, and drive the output.