Rain Sensor

I am searching for a RAIN sensor that will compatible with my CPU 212 SIEMENS plc.


a cheap want will do as its for a small prototype only. any brands or do anyone have any?

CAN a own circuitry rain sensor be done and connect it to the plc to trigger the output.

Need some feedbacks and comments from you all.
Please do guide me. Thank you.

If you want to try to make your own for a test, you might try this:
http://icecreamterror.wordpress.com/2009/09/09/arduino-rainmoisture-sensor/

You could use the Arduino to fire a relay to send a signal to your PLC

use the Arduino to fire a relay to send a signal to your PLC. how this can be done?

I guess it might be beyond you.

The Arduino is a micro controller board with digital outputs. You would use one of these to power a relay and send your PLC voltage through the relay to an input on your PLC.

If this doesn't make sense to you then perhaps you are better to look in another direction.

We have used these, they work pretty good if you can keep trash out of the collector. It measures in .01" or .2 mm. You use a digital input and just count up each pulse. http://www.davisnet.com/weather/products/weather_product.asp?pnum=07852

Here are links to Vivi's two (and counting) other threads on this same project:

http://www.plctalk.net/qanda/showthread.php?t=69339&page=6
http://www.plctalk.net/qanda/showthread.php?t=69735&page=5

Vivi,

From experiments, using the circuit in Post #2, even if you leave off the resistor, your S7-212 24 volt DC input will probably not go on when water is between the two electrodes. You will need some other medium placed between the two electrodes so that when it is wet, the resistance is very low. Maybe a sponge with some acidic dry material on it would be conductive when it gets wet.

Vivi,

Another option is to use a small float switch mounted in the bottom of a small container. When rain fills the container to some low level, the switch will go on and send an ON input to your S7-212 Input I0.0.

You could use a low-cost level switch such as the Omega LVK-130. Mount it in a very small-diameter can so that it will not require much rainfall to trip it. Pre-fill the container up to the bottom of the float, and drill a small hole in the side of the container just above that point. Now any significant rain will fill the container and raise the level to trip the switch. Continued rainfall will keep the level high enough to keep the float switch closed. After it stops raining, the water will drain down through the small hole in the side, allowing the float to drop and open the switch. The Omega Engineering LVK130 is $22 US, but you may find a cheaper switch, or even make your own with a ping-pong ball and a small limit switch.

http://www.omega.com/ppt/pptsc.asp?ref=LVK130_140_150_190&Nav=grek13

For classroom demonstration, place the first small container with the float switch into another larger container so that the water can drain out without spilling on the floor!

If you are good with tools, you could build your own using a snap-action limit switch, such as the Digi-Key SW513-ND ($7.90 US). Mount it upside down in the top of your container, then make a float with lever rod to trip the switch (similar to a toilet-bowl ball float with rod). See this link for the switch:

http://search.digikey.com/us/en/products/D2FW-G083M/SW513-ND/307736