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.
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.
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.
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.
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.
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.
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.
Optical rain detection systems typically work by launching IR light into the
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
A simple system, the clever parts are establishing the launch and receive
locations such that the system works reliably without lots of unnecessary
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.
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
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