Sensor flow water

yes, friends, i wish build a proyect to garden and i would like have a sensor what it can sense the flow. i think that there are several what send pulse when the water through it. I would like if you know any low cost sensor to this goal.

Best regards

you can get an old water meeter on ebay that have a pulse output for $20-$40. that is what i am going to use for my house so the chlorine pump always pumps the right amount of chlorine for the amount of water used instead of just feeding it when the water is being used without knowing how fast it is being used

Ok thank you wediggers, i'll see this, Do you know which is the name of this device. Does it work fine with your system?.

Thank you

i have not finished setting mine up as i got a 1" Neptune meter and now am finding that it is hard to find 1" fittings for it (that are under $15) but i may just buy some of the more expensive ones or if i see a 5/8 or 3/4" meter with the pulse wire i may just get it. but i don't see many on ebay now but normally there are a bunch. sometimes they will say how many gallons per pulse in the auction but if not you can Google the model number and find the manual the one i got didn't have the pulse but i got it before i found the pulse ones and only paid $10 for it so i can't complain. but i am planing on taking the glass dome off and using a IR led or encoder to count the turns of the small flow meter to get my values

Seeed Studios has a smallish flow sensor that I've been wanting to try out.

http://www.seeedstudio.com/depot/water-flow-sensor-p-635.html

I have not used it yet, so no idea how exactly it works.