The Cyber-Spy.Com Usenet Archive Feeds Directly
From The Open And Publicly Available Newsgroup
This Group And Thousands Of Others Are Available
On Most IS NNTP News Servers On Port 119.
Cyber-Spy.Com Is NOT Responsible For Any Topic,
Opinions Or Content Posted To This Or Any Other
Newsgroup. This Web Archive Of The Newsgroup And
Posts Are For Informational Purposes Only.
From: firstname.lastname@example.org (N. Thornton)
Subject: Re: Rain intensity to voltage idea... Opinions?
Date: 5 Oct 2002 12:55:28 -0700
NNTP-Posting-Date: 5 Oct 2002 19:55:28 GMT
> In article ,
> NightRunner wrote:
> >I had an idea recently, see what you think of this...
> >A very low power, low frequency RF oscillator coupled to a simple
> >diode detector and DC amplifier. The coupling would be a very low
> >capacitance grid etched from copper clad board like this:
> >Over the top of this (indeed, comprising the top of the waterproof
> >box), would be placed very closely a thin plastic sheet. My theory is
> >that rainwater resting on the plastic film would create a bunch of
> >series capacitances between the raindrops, the film, and the finger
> >traces... Thus the more water at a given moment, the greater the
> >amount of signal reaching the detector. The board and film could be
> >VERY carefully bowed to allow the rainwater to roll off gradually to
> >prevent pooling. Might of course make better sense to use a sheet of
> >flexible plastic with copper tape to make the grid rather than etch it
> >from copper clad board.
> >The waterproofed nature of the enclosure would eliminate any
> >possibility of corrosion of probes, particularly if you toss a couple
> >of silica gel packets into the box before sealing.
> >The DC amplifier could be simply an op-amp volatge amplifier, and then
> >this output could be measured directly on a meter or fed via cable
> >into a simple serial port ADC for graphing on a computer.
> >The grid itself would no doubt need to be worked at to achieve best
> >results over the range of misty sprinkles to heavy downpours.
Golden rule: tell us the app if you can.
It should work. Maybe you could put the copper traces on the inside of
the box, more sensor area needed, then you've got nothing visible
externally, nothing exposed, no holes to make... ya?
>I really wasn't after alternatives to my idea, although I do
>appreciate the offer. What I want to know is, does my concept just
>work, or is it workable?
should work fine.
>Here's an interesting method along the lines of using probes. Use
>carbon pencil leads (like drafting compass refills) instead of metal
Thats should work fine too if you use a pot track, so its not brittle,
and use enough of them to get enough area to catch at least one
raindrop. Muck tends to lower R over time, but that can be compensated
for. I prefer your first idea tho.
>This is used for automatic windshied washers.
>The problem is that you're going to get a sawtooth wave as water
>up then runs off in sheets. The amount of water on the plates is
>related to water's surface tension than the rate of rainfall. I
>think the sawtooth frequency will be reliable unless you keep
Use a delay so it knows its atill raining. Even if its stopped :)
Go Back To The Cyber-Spy.Com
Usenet Web Archive Index Of
The sci.electronics.design Newsgroup