Rain Detector

On Thu, 28 Aug 2008 20:24:44 +0100, Rick Hughes wrote:

Plenty of kist available try Maplins. As you say the sensor is the biggest problem. How about a few square inches of veroboard? Give it a rub over with some fine sand paper to remove the protective lacquer and connect alternate strips to each sensor wire. Copper will last for ages outside, not so sure about the SRPB board that might give up in a year or two.
--
Cheers
Dave.




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I don;t think it will, copper circuit board tracks which is what veroboard is tarnish very quickly within weeks. Most circuit boards are coated with a protective layer to stop this oxidation process.
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On Wed, 3 Sep 2008 13:11:16 +0100, whisky-dave wrote:

So why is copper still occasionally used as roofing material if it doesn't last... I don't think copper oxide, or copper salts depending on the pollution in your area, are insulators unlike say aluminium oxide.

Main reason is so you don't have to mechanically clean the tracks before soldering rather than corrosion eating them away. Coatings post assembly are to stop damp or muck shorting tracks or getting at the board.
--
Cheers
Dave.




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Send out the bald man?
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Waldo Point wrote:

Send out a tall man for early warning of rain. ;-)
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on
Replace the coins sensor with.... A spoon and a tilt switch, spoon should have a small brass tube piece welded directly in the center of its balance. take a longish bolt and some nuts that will fit through the brass tube piece,this nut and bolt will go through a wooden upright support drill on both sides at exactly the same height,feed the bolt through hole on one side and screw on 2 nuts,take spoon and feed it on to bolt,put another 2 nuts on the bolt feed bolt through the other hole and put a last bolt on the end. Now then tighten the 2 end nuts (1 on the bolt head side) so that the bolt does not move in the holes,glue(araldite or some strong glue) the tilt switch to the end of the handle and connect to a buzzer and battery,tighten the 2 center nuts(possibly need washer either side of the nuts?) against the brass tube ever so slightly but enough to give the spoon freedom to move.
get some water and pour droplets onto the spoons hollow and it should drop down forcing the tilt switch to activate the buzzer,the 2 center nuts will probably need adjusting for sensitivity.
Any good panel? :-) That came of the top of me head whilst waiting for the kettle to boil.
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On Fri, 29 Aug 2008 00:46:14 GMT, George wrote:

Complicated, why not use the handle end of the spoon as one contact and a bolt head as the other. It won't detect light rain fall either, even if you put a large funnel over the bowl of the spoon to capture more rain.
What you have described is the basis of a "tipping bucket" rain gauge. What you have missed is that the bucket (spoon) tips it empties of water and is ready for the next volume of rain.
This would only signal a pulse to the detector, so that would need to trigger something to sound the alarm long enough to be noticed. Unlike the "wet plate" detector which will sound for as long as the plate is wet.
--
Cheers
Dave.




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Water detector alarm http://www.greenweld.co.uk/acatalog/Smoke_and_Water_Alarms.html
http://www.dalbani.co.uk/index.php
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These sort of circuits are generally kids' projects. If you want the sensor to last you need to avoid any dc on the sensor, to avoid galvanic corrosion. Generate ac and feed it to the sensor, using it with another C or R as a voltage divider. Level of output voltage drops when wet, use that to trigger your yes/no circuit.
NT
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An optical sensor might be better, what do they fit to modern cars these days? the auto windscreen wiper seemed to work OK on the Peugeot 807 I used to have . Don
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On Sun, 31 Aug 2008 08:31:30 +0100, in uk.d-i-y "Donwill" <popple @diddle .dot> wrote:

Yes, wife has a 206 and its auto wiper works well (provided you can remember the switch flick-sequence to activate it!). And it's inside, so doesn't get wet. It detects wetness on the other side of the glass. Could it use a light beam totally reflected at the glass surface, but passing through when the surface is wet - or the other way round? It has a very fast response, generates single sweeps in light rain.
Phil
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Phil Addison wrote:

Our Mazda 3 Sport has an optical system. I assume it works on uneven spread of light when raindrops fall on the outside of the windscreen where the sensor is on the inside. Trouble is I often drive it in the dark on unlit roads and if there are not a lot of oncoming headlights it does not work well enough. My wife tends to use it in daylight and reckons the system is brilliant.
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Invisible Man wrote:

Optical rain detection systems typically work by launching IR light into the windscreen.
The light is confined to the windscreen through total internal reflection (TIR)
When there is water present on the windscreen it no longer undergoes TIR, but is effectively coupled out of the glass, resulting in a drop in the received signal.
A simple system, the clever parts are establishing the launch and receive locations such that the system works reliably without lots of unnecessary triggering.
On coming light should not really be a problem providing the operating wavelength is well chosen and the receiver appropriately filtered. I would also assume the light source is modulated at a few kHz, which is a standard technique to reduce unwanted background levels.
cheers
David
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Until someone makes an IR transmitter to fit to their car just to turn on other peoples wipers as they drive around. 8-)
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The 206 one is not bad, but there are times where a manual sensitivity control would be useful. Some patterns of rain seem to trigger the unit incorrectly such that you have to do a manual sweep occasionally. However, if a large drop of rain from a tree or something hits in the right location you get a single wiper shot to slurp it up. Usually impresses people. Simon.
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