Rain sensors

Goody · Apr 14, 2007

I, at last am starting my garden project - an auto watering system.

But I dont want just a plain dumb water every day at the same time thing. I want my plc to make decisions.

I am installing pipes and tubing and valves to water everything from the main flower and vegetable beds to strawberry box's and hanging baskets of flowers.

Different things will need differing amounts of water and at different times.

I would love to make/buy a rain sensor that I can interface with an input to the plc. Just a digital input that can tell me how long it has rained. I am using a electro/thermostat for the temperature - but if I want this thing to be at least semi intelligent I want a rain sensor.

I am having all sorts of ideas how to make one - the idea first struck me when I watched my cars auto rain sensing wipers. I dont really know how they work. I suspect it is some kind of diffuse light caused by the rain drops but I could be way out.

Does anybody know how to make one - or has anyone or has anyone any ideas.

The little PLC has only digital inputs so really it has to be a on off thing.

Bob O · Apr 14, 2007

Goody,

I thought about doing something similar in the past but I was going to check the moister content of the soil to determine if it needed water.

A search for moister meters leads me to some humidity sensors for the soil that would indicate when you should water.

Maybe this will help.

Bob

TConnolly · Apr 14, 2007

Try googling things such as 'ground moisture sensor' or 'lawn water sensor' or 'garden sensor' or 'irrigation sensor' etc. I'm not sure what you will find in the UK, but on our side of the pond we get a bit over fanatical about our lawns so even the small towns have an irrigation supply house. I use controllers and sensors from these guys: http://www.hunterindustries.com/ A 9 zone irrigation controller is usually less than a hundred bucks (51 pounds), so a PLC is an expensive way to go.

Edit: It looks like Hunter irrigation products are available in the UK. http://www.evenproducts.com/

Andy · Apr 14, 2007

found this if it is of any use
http://www.autolawnsprinklers.com/2006/07/rain-sensors-do-you-have-one.html
Or
How about having a vessel fitted with float switches so if it rains it fills up and inhibits the cycle for a set time ?
or use some type of level sensor that senses a float in a vessel, look for a change in the level sensor signal to determine if its raining
just a simple idea if it helps
have you thought about collecting rainfall so you conserve water?
try
http://www.smarthome.com/7197.html

10BaseT. · Apr 14, 2007

Goody said:
I, at last am starting my garden project - an auto watering system.

But I dont want just a plain dumb water every day at the same time thing. I want my plc to make decisions.

I am installing pipes and tubing and valves to water everything from the main flower and vegetable beds to strawberry box's and hanging baskets of flowers.

Different things will need differing amounts of water and at different times.

I would love to make/buy a rain sensor that I can interface with an input to the plc. Just a digital input that can tell me how long it has rained. I am using a electro/thermostat for the temperature - but if I want this thing to be at least semi intelligent I want a rain sensor.

I am having all sorts of ideas how to make one - the idea first struck me when I watched my cars auto rain sensing wipers. I dont really know how they work. I suspect it is some kind of diffuse light caused by the rain drops but I could be way out.

Does anybody know how to make one - or has anyone or has anyone any ideas.

The little PLC has only digital inputs so really it has to be a on off thing.

If you have a merc with their renowned electrics and use the same technology, you can guarantee that your garden will look like the Gobi Desert after a week .

rsdoran · Apr 14, 2007

You may be interested in this topic: http://www.plctalk.net/qanda/showthread.php?t=21890&page=2&pp=15

Bob O · Apr 14, 2007

I was in an agricultural store this afternoon picking up non-agricultural stuff when I noticed in the bargain bin was a moister meter from Bond [I think] for $2.89 and no batteries required. Maybe this will help and maybe it won’t.

godfrey · Apr 14, 2007

Yes, we all know doing this with a PLC is more expensive but being controls guys, we know it's for the fun of it.

CharlesM · Apr 14, 2007

You may want to search for a "rain switch"

http://www.lawnh2o.com/toro/toro_sensors.htm

http://www.google.com/search?q=rain+switch&rls=com.microsoft:en-us&ie=UTF-8&oe=UTF-8&startIndex=&startPage=1

504bloke · Apr 15, 2007

Goody you could make your own rain sensor

2 x S/S rods, 1 Collector pot with fine holes in it and a level sensing relay for the probes with a relay output.

When it rains the pot fills, the probes conduct, the relay switches, when it stops the pot empties and the probes stop conducting and the relay drops out.

In fact use a metal pot and you'll only need one probe or make something up to fit in your gutter ?

davefinic · Apr 15, 2007

I have fitted rain sensors on projects to auto close roof vents with pnuematic actuators in the past the sensors would monitor for rain just like the sensors on a car. they have a small heater built in to remove small amounts of water build up.

These were supplied to me free issue by the client but i could try to find the supplier if you are interested.

MrDave · Apr 16, 2007

Here is a link to a common rain sensor that uses contacts.

http://www.hunterindustries.com/Products/Sensors/miniclikintro.html

JohnW · Apr 16, 2007

Try this

http://www.casellacel.com/Products/Detail.asp?ID=621

It gives a switched output per unit measured.

mcw999 · Apr 16, 2007

Rain switches are very simple and cheap. There are two that I would suggest. One is from Hunter, the Rain Clik, comes in both wireless and wired versions. This kind uses hydroponic discs to close a contact, when they get wet, they expand, pretty simple. The other is the "cup type", which Rain Bird makes. Also very simple, if rain fills the cup it shorts out two screws which then closes a set of contacts. Both can be purchased for under $30.00.

Von · Apr 16, 2007

Good one JohnW,

Goody, that was my first thought too, not just to know that it rained but how much it has rained! These "tipping" type rain gauges are available from many vendors in many proce reanges. You'll get a pulse for every "tip" and can be bought for english or metric measure.

Rain sensors

Goody

Member

Bob O

Member

TConnolly

Lifetime Supporting Member

Andy

Member

10BaseT.

Member

rsdoran

Lifetime Supporting Member

Bob O

Member

godfrey

Member

CharlesM

Member

504bloke

Lifetime Supporting Member

davefinic

Member

MrDave

Member

JohnW

Member

mcw999

Member

Von

Member

Similar Topics