Rain Sensor

T

the old fart

Senior Member
Hi again Guys,

I've search the site,

I'm looking to place a sensor on the conservatory roof to detect the first drops of rain.

Want a sensor that will last, so it will need to be sealed.

Thinking of using a copper sheet, sealed, connected to a touch input.

Ideas please.

Dave
 
A

AllyCat

Senior Member
Hi Dave,

You need just a few drops of rain to change the capacitance between a "touch" input pin and ground (Vss of the PICaxe). So I would try a few square inches of stripboard ("Veroboard") with alternate tracks connected to the pin and to ground and mounted under a thin insulating film. Don't know if it will work, but it should be easy to test. Then you'll need to use PICaxe software which can accommodate slow changes in the oscillator frequency (touch value) without false triggering.

As far as commercial units are concerned, this is perhaps the "Rolls Royce", but not wildly expensive if bought directly from the manufacturer (was also available from Amazon and now directly from a UK distributor).

Cheers, Alan.
 
T

the old fart

Senior Member
Hi Alan,

I have a veroboard drying overnight. I coated it in model enamel paint.

Watching the touch16 results change as it dries.( via a plugin OLED display)

failing that, will try this from ebay,


at 99p it might not work!!!

Dave
 
A

AllyCat

Senior Member
Hi Dave,

Well you can't complain about the price, even with shipping (which may take a few weeks of course).

I wonder if it just uses conductivity (e.g. the DIP is a Comparator or Op-Amp) or if it's capacitive (which might be possible with a double 555 timer, for example)?

Cheers, Alan.
 
Z

ZOR

Senior Member
What happens to morning dew, fog? Maybe listen for noise? I know I soon hear rain on my conservatory roof, some sort of sensor mounted internally under the roof material. Just a thought.
 
1968neil

1968neil

Senior Member
Just throwing this in the mix for clarity.
Some cars have automatic windscreen wipers and this is the method of operation

"The sensor is located behind the rear-view mirror on the inside of the windscreen and transmits an infra-red beam onto the screen at a certain angle. The beam is reflected back differently according to the amount of water on the windscreen. The amount of light reflected controls the wiper cycle from single flick-wipe to continuous wiping. To avoid icing or condensation, the area around the sensor is heated." (extracted from the vehicles technical manual)

So i would hazard a guess you could use a cheap infra red emitter and monitor the output level using adc, obviously will need some experimenting with but totally feasible i would imagine that the hard work would be in finding the angle of best operation.
You could try a basic experiment with an LDR and see what light level changes you get when it rains and the roof is wet, obviously infra red is going to be more consistent with the light levels but should give you an idea of the complexity required to achieve your desired results.

Regards
Neil
Rainsensor_715x230.jpg
 
premelec

premelec

Senior Member
If you really want to detect "first few drops" I think sound would be your best bet - a sheet of something connected acoustically to a microphone - electret or piezo... distinguishing from birds, rats and wind noises is the difficulty - large blobs of water likely have a particular sound. Once you get a torrent of rain all bets are off with regard to sound. You might try a plastic cone waterproof speaker in a box exposed to droplets and look at the signal [very low voltage to be raised through a transformer or amplifier] that comes out... problem with this is accumulating water - need some holes in plastic speaker cone... :-0 I'm suggesting this from my many decades of listening to first drops on house roofs, car roofs and camp tents....
 
T

the old fart

Senior Member
AllyCat said:
I wonder if it just uses conductivity (e.g. the DIP is a Comparator or Op-Amp) or if it's capacitive (which might be possible with a double 555 timer, for example)?
.
Click to expand...
Looking at tech sheet, it give a variable reading for 'readadc' input.

Theory is.

Washing out.
switch unit on.
auto null reading.
increase in reading, set alarm.


Dave
 
Last edited:
D

Dippy

Moderator
What is your device going to do when the first drops fall?
And on a cold day those drops will stay there for hours.

A car sensor is under the wiped area so the rainfall detection is continually 'updated'.
And therefore it also gets 'cleaned' wrt dirt, bird-doos and rampant insects.

Where are you going to mount the cheapo one?
Get one and experiment - that's the easiest way.
 
Hemi345

Hemi345

Senior Member
What is the purpose of detecting the first drops of rain? Trigger an alarm to close the windows or something? Could you use something like THIS with a dumb serial link (the rain gauge is 433mhz)? The description on Sparkfun for a very similar rain gauge (if not the same one) says:
The rain gauge is a self-emptying bucket-type rain gauge which activates a momentary button closure for each 0.011" of rain that are collected.
Click to expand...
 
erco

erco

Senior Member
@OF: The WASH?

Save your picaxe for a better task. Use the cheap sensor shown in your post #4 (better yet make or etch your own) to trigger an SCR and a loud beeper. Under $2 and you're done.
 
P

Paix

Senior Member
Motorise the washing line on pulleys, so that it brings the washing under cover at the first sign of rain, with a manual reset to send it back out again if the rain has passed. That would make it a worthy project and put your feet up.
 
D

Dippy

Moderator
That's a neat idea.

Mind though, this time of year in UK it's time to buy a Tumble-dryer.

Then use the PICAXE to make an auto-stop when the washing is dry. . :)
 
S

sedeap

Senior Member
Not Picaxe inside, but working

I made this Rain Notifier a few years ago... and still working...
Just cut a bottle of soda in angle, keep the neck and cap, drill a small hole on a side of the cap to enable spill and insert 2 stainless wires close enough to hold a droplet in between.
Connect the wire probes to a sound box notifier with flat cables not too long (I use 50cm)
With a 9v PP battery, you will be notified in 20Meters range, guaranteed
The Notifier was made with a Mylar plastic speaker, and a CD4093 NAND logic gate, plus resistors and capacitors.
(Sorry, no Picaxe inside) but 2 pictures may help.
RainDetector.jpgRainNotifier.jpg
C.U Pals
 
T

the old fart

Senior Member
Update.

The cheepo 99p unit from ebay arrived.

unit gives an ADC value around 1020 when dry, down to 300 when saturated.

by looking for the value dropping by 50, the alarm sounds.


Code: 
;20m2 raining


;c.0 
;c.1 adc sensor
;c.2 
;c.3 total reset 
;c.4
;c.5
;c.6 out to sounder
;c.7 out to display


;B.0 - B.7 Leds



symbol actual=W3
symbol target=W4
symbol diff=w5
symbol reading=W6
symbol auxWord=W7
let diff=50
start:

low 7,6,5,4,3,2,1,0 ;Leds on

pause 2000
readadc10 c.1,actual

target=actual-diff

low c.7
pause 500

serout c.7,N2400,(254,1)
pause 30

high 7,6,5,4,3,2,1,0 ;Leds off



main:

if pin3=1 then goto start


readadc10 c.1,actual

auxword=target+diff

if actual > auxword then let target = actual-diff:endif



reading= w3-w4:

if reading >85 then let reading = 0:endif
gosub leds


	SEROUT C.7,N2400,(254,128,"actual ",#w3,"   ")
	serout c.7,n2400,(254,192,"target ",#w4,"   ")
      serout c.7,n2400,(254,148,"  diff ",#w6,"   ")

if w3<W4 then tune C.5, 3, %0000000,($40,$05,$49,$05,$40,$2B,$C7,$45,$04,$47,$04,$64,$29,$C5,$40,$05,$49,$05,$40,$2B,$C7,$45,$04,$40,$02,$44,$85,$40,$42,$44,$45,$8C,$42,$44,$45,$47,$8C,$42,$44,$45,$47,$0C,$42,$44,$45,$47,$0C,$00,$44,$85):endif


;tune c.5, 1, %00000000,($1)

	serout c.7,N2400,(254,147,"R")

	SEROUT c.7,N2400,(254,212,"                   ")
	
	
	IF W3<W4 THEN SEROUT c.7,N2400,(254,212,"--WARNING RAINING--"):ENDIF

	serout c.7,N2400,(254,147," ")

goto main


leds:

if reading>45 then low 7 high 6,5,4,3,2,1,0:goto ledsend:endif
if reading>40 then low 6 high 7,5,4,3,2,1,0:goto ledsend:endif
if reading>35 then low 5 high 7,6,4,3,2,1,0:goto ledsend:endif
if reading>30 then low 4 high 7,6,5,3,2,1,0:goto ledsend:endif
if reading>25 then low 3 high 7,6,5,4,2,1,0:goto ledsend:endif
if reading>15 then low 2 high 7,5,5,4,3,1,0:goto ledsend:endif
if reading>5then low 1 high 7,6,5,4,3,2,0:goto ledsend:endif
low 0 high 7,6,5,4,3,2,1

ledsend:

return
 
C

crowland

Member
I tried a Veroboard rain sensor connected to a touch input and it seems to show some potential.

The board has alternate strips connected to the touch input and ground and, for now, some plastic tape to insulate it.
Dry it gives a touch16 value of about 12700, with one large drop giving 13000, increasing as more drops are added.

I'm going to try removing alternate strips to see what effect it has.

I plan to have a series of resistors glued to the underside of the board, these will heat the board to evaporate moisture. I'm thinking of a PWM driving a MOSFET to provide heater control. I wouldn't be surprised if this needs to be off during measurments.

The reason for this is to have something that will alert me when it starts raining so I can rush out and get the telescope in or covered. It's also going to have a MLX90614 IR temperature sensor as a cloud detector. Maybe one of those Maplin wind meters as well.

Chris
 
T

the old fart

Senior Member
crowland said:
I tried a Veroboard rain sensor connected to a touch input and it seems to show some potential.

The board has alternate strips connected to the touch input and ground and, for now, some plastic tape to insulate it.
Dry it gives a touch16 value of about 12700, with one large drop giving 13000, increasing as more drops are added.

I'm going to try removing alternate strips to see what effect it has.

I plan to have a series of resistors glued to the underside of the board, these will heat the board to evaporate moisture. I'm thinking of a PWM driving a MOSFET to provide heater control. I wouldn't be surprised if this needs to be off during measurments.

The reason for this is to have something that will alert me when it starts raining so I can rush out and get the telescope in or covered. It's also going to have a MLX90614 IR temperature sensor as a cloud detector. Maybe one of those Maplin wind meters as well.

Chris
Click to expand...
Hi Chris,
I never had a lot of luck using vero board.

try this from ebay, it worked well for me,

mounted it on top of the conservatory roof.

Dave.
 
C

crowland

Member
Yes, I saw your report Dave, but doesn't this rely on conductivity? I'm a bit uneasy about that because it will corrode, even rain water isn't that pure.

There's some other interesting stuff on that site.

Chris
 
T

the old fart

Senior Member
The board is coated with something or other, so fingers crossed.

Bare copper track will turn green very quickly.

I tried the touch command, but was not impressed with its use for this project.
I use the ADC from the 99p board, which allows for auto stabilization of the circuit in the program. If board dries out then threshold alters to suit.
On board is a variable resistor to setup an on/off input.

The pcb is fitted so that water can run off the board, about 20deg from horizontal, and it faces the the general position of the sun to help drying.

for 99p its worth a try.

Dave
 
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