Cheap(ish) rain sensor?

[NJ Roadmap]

Ok so this is what I'm getting (albeit a glorified and readymade version of the PCB idea posted on here) as I'm a bit short on time. Cost £40 but I reckon it can be built for about a tenner. It runs at 12V @250mA, ideal for me.

**broken link removed**

Silly question now: I need to step-down 12V to 5V logic. I'm guessing the simple solution is a voltage divider. I however need to protect my PIC from over-current, so I'm guessing high-value resistances in the divider should do it?

 

[hjl4]

AC as in square-wave.

What??? AC is in technical terms a sine wave.
Your square wave produced by the PIC, is actually just a pulse train.

If I'm wrong, tell me how the PIC creates a negative voltage.

Just curious, and I am not hijacking this thread.

Good day.

 

[Nigel Goodwin]

What??? AC is in technical terms a sine wave.

Nothing of the kind, AC can be any waveshape, a squarewave is perfectly acceptable.

Your square wave produced by the PIC, is actually just a pulse train.

If I'm wrong, tell me how the PIC creates a negative voltage.

Why would you need a negative voltage?.

 

[hjl4]

Hmmm, I guess your right, I never thought of it that way, probably because in electronic class, I was taught that AC = alternating current, which is + and - wave. (sine wave that is).
A constant wave of +5v for example, going from +5v to 0v, is just a pulse train. (A square wave).

In terms of preventing corrosion due to the galvanic process, you would need + and - voltage.

I guess I should brace myself, for the onslaught of replies now.

Who knows, maybe I will learn something.

 

[Roff]

Hmmm, I guess your right, I never thought of it that way, probably because in electronic class, I was taught that AC = alternating current, which is + and - wave. (sine wave that is).
A constant wave of +5v for example, going from +5v to 0v, is just a pulse train. (A square wave).

In terms of preventing corrosion due to the galvanic process, you would need + and - voltage.

I guess I should brace myself, for the onslaught of replies now.

Who knows, maybe I will learn something.

Take a 0 to 5V square wave, put a capacitor in series with a resistor to ground, and voila! Across your resistor, you get a +/-2.5V square wave!

 

[philba]

I think the "tilted board with fingers" approach would not be able to distinguish condensation (.e. dew) from real rain. And not be able to tell how much is falliing. It's fine if all you want is to know if there is moisture in the atmosphere.

The auto rain sensors can tell the amount of rain. I think they use an IR reflectivity approach but that's just a guess. The sensor on my wife's volvo points out the top center of the windshield (no holes or coatings) and she gives me "da steenk eye" every time I start poking around there. I suspect that dirt is an issue.

 

[Rolf]

I think the "tilted board with fingers" approach would not be able to distinguish condensation (.e. dew) from real rain. And not be able to tell how much is falliing. It's fine if all you want is to know if there is moisture in the atmosphere.

{snip}

The originator of this thread stated that he just wanted a rain indicator, NO amount.
I didn't think you could have dew unless the object was colder (dew point) than the atmosphere. This sensor will be at the ambient temperature most of the time so I don't think there should be any problem. If there is it can be fixed with a small heater, light bulb under it.

 

[Leftyretro]

This is one of those kind of projects that unless you really want to design and build for personal pleasure and accomplishment, that might better to purchased.

This last Christmas I had to bring a gift to an office party for a drawing type event. The rules are all gifts had to be worth less then $20. I went to a nearby Target department store and looked at their gift suggestion isle. I found a wireless digital rain and temp gauge, made in China of course, costs was $20!.

It uses the classical tilting bucket for rain amount and standard temp sensors in both the outside sender unit and in the indoor receiver. The display has some histogram displays and normally just rotates display from indoor and outdoor temp and a bar graph showing daily rain bars for the last 7 days. Range is said to be 600 feet, but I haven't tested range yet, but works well at 50 feet in my use. Anyway I ended up winning the gift I brought so that is how I ended up with this thing.

$20! could anyone realisticly design and build such a thing for that little?

Lefty

 

[Rolf]

Question........

This is one of those kind of projects that unless you really want to design and build for personal pleasure and accomplishment, that might better to purchased.

This last Christmas I had to bring a gift to an office party for a drawing type event. The rules are all gifts had to be worth less then $20. I went to a nearby Target department store and looked at their gift suggestion isle. I found a wireless digital rain and temp gauge, made in China of course, costs was $20!.

It uses the classical tilting bucket for rain amount and standard temp sensors in both the outside sender unit and in the indoor receiver. The display has some histogram displays and normally just rotates display from indoor and outdoor temp and a bar graph showing daily rain bars for the last 7 days. Range is said to be 600 feet, but I haven't tested range yet, but works well at 50 feet in my use. Anyway I ended up winning the gift I brought so that is how I ended up with this thing.

$20! could anyone realisticly design and build such a thing for that little?

Lefty

Yes, there are some nice remote reading gadgets around, at very reasonable prices.
So how long will it take to trip the bucket after a moderated rain starts?
I would also like to see a picture of the bucket arrangement.

 

[gramo]

I just had an idea that I had to share,

What about using a flow meter? Throw it under a funnel and it will send out X many pulses per litre of water! Now you can detect rain, how much rain, and not be as concerned about lifing, as the flow meters are designed for such a job

 

[NJ Roadmap]

I guess that would work just as well as long as the meter is sensitive enough to detect small flows, i.e. in millilitres.

 

[NJ Roadmap]

Ok so this is what I'm getting (albeit a glorified and readymade version of the PCB idea posted on here) as I'm a bit short on time. Cost £40 but I reckon it can be built for about a tenner. It runs at 12V @250mA, ideal for me.

**broken link removed**

Silly question now: I need to step-down 12V to 5V logic. I'm guessing the simple solution is a voltage divider. I however need to protect my PIC from over-current, so I'm guessing high-value resistances in the divider should do it?

Bumpedy Bump.

 

[gramo]

Heres a basic circuit for a PIC to operate (PICs with internal oscillators will not need the external crystal)

**broken link removed**

 

[gramo]

Some PICs have 1 or 2 Vdd / Vss Pins, be sure to connect them all. Pin numbers will differ from PIC to PIC.

The 7805 is a 5V voltage regulator. They cost about 30 cents

Note that the 0.1uF is a tantalum capacitor, the 22pF are ceramic capacitors and the 10uF are electrolytic capacitors.

 

[NJ Roadmap]

Umm I know how to do that, thanks anyway.

I'm wondering about how I step down the 12V output from the rain sensor to TTL levels. I guess a 7805 would do the job but its a bit pointless if I know what the input level to it is going to be (12V 250mA). So thats why I was wondering if a simple voltage divider would do..( obviously with high value resistors to limit the current into the I/O pin of the PIC)

 

[NJ Roadmap]

p.s. The rain sensor sends me a 12V output when it senses rain. Else 0V.

 

[Nigel Goodwin]

p.s. The rain sensor sends me a 12V output when it senses rain. Else 0V.

If you're feeding a PIC a simple series resistor is all that's required (anywhere from 10K to 100K would be fine), or you could use two resistors as a simple potential divider, ratio 7:5.

 

[NJ Roadmap]

Thanks I planned to used the potential divider for awhile but when the sensor arrived today I found that it had dry contacts so I'm just wetting them with 5V and sending the output straight to the PIC.

 

[NJ Roadmap]

p.s. Pretty damn awesome sensor. I wish the company'd tell me what kind of digital filtering's on it.

 

[gromikov]

Here is the link for a rain sensor:
https://www.aaroncake.net/circuits/lie.asp
It was posted last year on this forum.