It would be handy to be able to have a detector that can give an audible signal when it starts to rain.
I often have sports kit outside drying (Scuba, boat etc) and can't rely on it staying dry long enough to dry kit.
I have found a link to one project
Rick Hughes coughed up some electrons that declared:
Stainless steel would last forever, more or less. When I was a kid, I made a water level detector for a caravan water tank (Aquaroll) with 5 bits of stainless rod bent around the pipe-straightener that dipped in the container. One common and 4 sensor points. Connections were done with crimped stainless wire, sleeved and run out of the container, then soldered into a DIN plug. Worked very well, never corroded.
Anyway I digress.
Perhaps get something like (anything will do as long as it's got stainless rod):
Lay in a pattern like this:
---------------- ================
---------------- ================
---------------- ================
Connect the --------- together, connect the ============ together, but separate from the ----------
Epoxy down on a bit of plastic (outside of a waterproof box if you want keep it self contained, with the electronics inside). Space rods so that a drop of rain can couple two rods.
If you don't fancy trying to solder the rod, what I did was hacksaw a 1/8" slot in the end, then use a heavy vice to crimp a bit of wire in the slot. If you're using copper wire, a bit of solid core from some mains twin+earth might work, but cover the crimp with epoxy.
Well, that's my theory. Sure there'll be many more equally good ideas. The above will cost you a few pounds depending if you get lucky at the pound shop for the stainless and whether you need to buy appropriate solder and flux.
Cheers
Tim
We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Rick Hughes" saying something like:
Stainless steel probes - I've never tried soldering to stainless, it might be ok.
Isn't a Scuba kit supposed to be wet? and how do hang a boat on the washing line?
Veroboard with alternate strips commoned to each sensor wire?
Alternatively, a well-trained cat[*] that doesn't like getting wet and will come and ask to have paws dried, will alert you to a change in weather conditions.
3rd option: a canopy over the washing line, that descends when a piece of blotting-paper gets wet.Owain
[*] this is of course an illusion, you find a cat that doesn't like to get wet and has trained you to dry its paws whenever it comes in.
You'd be amazed how much a wetsuit will smell if left damp for a few days. And even synthetic sails will get mildew stains.
OP might like to google for wetsuit enzyme too.
Andy
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.
Send out the bald man?
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.
Water detector alarm
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.
Send out a tall man for early warning of rain. ;-)
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
That was the basis of one in Everyday Electronics which I made well over 30 years ago. You need to heat it too (a few low power resistors are sufficient), or it can takes ages to dry out and stop reporting rain, when the rain stopped ages beforehand, and it might otherwise be triggered by condensation.
I think I've seen a simple module in Maplin which works much the same way.
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
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
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.
when in use yes :-)
afterwards you need it to dry ... as to boat, typically covers left off it trying to dry it out, usually gets close to dry ... then it rains, and before I notice ... 'tis all wet again.
I made the same one ... I even still have that issue of the magazine ! The problem will be long term stability with veroboard in open air ...
The only one I could find on MAPLIN was the Velleman MK108 kit ...
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