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DC & AC

Posted: Thu May 12, 2005 9:59 am
by kengwee
Hi!!! ive install a water sensor detector on the floor. The detector will send a "1" when there's a flood because during a flood the water will short the two metal poles under the detector. but the spec say that in order for the sensor to detect if there's water flood i must use 24Vac. does anyone noe why cant i use a 24Vdc to detect a short in water?

Re: DC & AC

Posted: Thu May 12, 2005 10:19 am
by philba
As stated, there is no way anyone can answer your question - you need to provide details about the gizmo. Like what is it??? <p>Oh, yeah, I forgot, the answer is 42.<p>Phil

Re: DC & AC

Posted: Thu May 12, 2005 12:52 pm
by L. Daniel Rosa
Come now Phil, or should I say Zaphod. The fleet isn't due until next week. There's no way one of the organic components of the only computer greater than Deep Thought could have found the ultimate question of life, the universe and everything.

Re: DC & AC

Posted: Thu May 12, 2005 2:06 pm
by terri
I thought the answer to the ultimate question of life, the universe and everything was an irrational number. Did someone round it up to 42?<p>[ May 12, 2005: Message edited by: terri ]</p>

Re: DC & AC

Posted: Thu May 12, 2005 4:51 pm
by peter-f
Well, looking on from my seat (in the Restaurant at the End of the Universe), I'd say it depends on what you paid for it... thus, how long you'll be abled to eat here! (What, with the accrued interest...)

Re: DC & AC

Posted: Thu May 12, 2005 5:33 pm
by dyarker
Because the detector was designed to use AC. With AC the electrodes erode slowwer, and build up less insulating crust, crudd and corrosion.

Re: DC & AC

Posted: Thu May 12, 2005 6:09 pm
by haklesup
I suspect it is rated for 15VAC because that is what outdoor irrigation systems are operated on. Never mind, they use 24VAC<p>Have you tried it with DC. It just might work. I wouldn't speculate on the performance without knowing what it is.<p>If the sensor works on a change of capacitance then I can see why AC is essential but if it is just a hydrophilic polymer (swells in the presence of water) that shoves a spring switch contact together, than it should work as well on DC as AC.

Re: DC & AC

Posted: Thu May 12, 2005 7:51 pm
by dyarker
He said, "... water will short the two metal poles under the detector ..."<p>If the unit simply rectifies the 24VAC input, AND does NOT use the 24VAC on the electrodes; MAYBE it will work from 24VDC.<p>keng, model name/number other info would have been useful.<p>[ May 12, 2005: Message edited by: Dale Y ]</p>

Re: DC & AC

Posted: Fri May 13, 2005 2:22 am
by Michael J
The AC is used to prevent the poles or contact points being eaten away by electrolysis.<p>"Any" DC voltage will eventually eat the electrodes to peices, with much more than about 2 Milliamps flowing it will be noticable in a few days, anything over a few hundred Milliamps
you can almost see happening, matter of hours.<p>Keng your unit probably reduces the AC voltage
or current and place it across the poles, but if
DC was used you would be replacing them on regular basis.

Re: DC & AC

Posted: Fri May 27, 2005 5:20 am
by kengwee
Hi folks!! sorry for the super late reply, ive finally got the water dectector spec. its a prduct from kele solutions, model WD-1B. Thx!!!

Re: DC & AC

Posted: Fri May 27, 2005 7:54 am
by dyarker
From their web page for
Water Detector Model WD-1B<p>"The Model WD-1B can be operated from 11-27 VAC/DC." Power it how ever you want within those limits.<p>(It took much longer to type this than to do a Google search on kele wd-1b!)<p>Everybody's comments above about probe errosion are true. The unit takes care of that internally apparently.<p>Cheers,

Re: DC & AC

Posted: Fri May 27, 2005 9:27 pm
by philba
This cracks me up. Original posting was about why the product wont work the way he wants it. We all go off in different directions about AC. With the data sheet, its clear, it will work the way he wants. I do love irony...

Re: DC & AC

Posted: Sun May 29, 2005 7:58 am
by kengwee
so sorry abt it, just that i my friend told me it wouldn't work and i dont have any spec to read... thx alot folks.... hehehe....