# Sprinkler Flow Sensor help

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#### cswanson

##### New Member
I'm going to try and sound as intelligent as I can about this. I was an EE minor in college, so I remember some stuff ;-)

I'm getting lawn sprinkler leaks, and I'd like to know exactly when my water in the irrigation system is flowing. I don't care how much is flowing, just an ON/OFF signal.

There are several flow sensors on the market, this seems to be the best one not completely locked into a proprietary controller:

It says:

The flow sensors generate a frequency which is proportional to flow
rate.... Power to operate the sensor is provided by the flow monitor... As
the liquid flow turns the impeller, a low impedance signal is transmitted
with a frequency proportional to the flow rate.

Like I said, I really just want ON/OFF, YES/NO.. so I can control a light or chirping buzzer with a relay or something.

Is there a fairly easy way to:
- send it power? 5V? 12V
- Determine that ANY "a low impedance signal" is being sent?

I'm handy with a soldering iron and a volt meter.. but not with this type of detail. I clearly don't want the $200-$500 full solution,

#### stevez

##### Active Member
I am trying to understand your situation and how a leak might be different from normal flow. I am trying to imagine a diagram of your system (the piping). I am thinking that there is a control valve that opens and closes - upstream of the control valve is the water supply - downstream are the sprinkler heads.

If there is a place where water is trapped under pressure - and a drop in pressure could indicate a leak then measuring the pressure for a short period of time after valves have close might reveal a leak.

It might be possible to measure the flow rate vs pressure to characterize the system with known good condition of the piping system. You would then monitor the flow vs pressure and signal an alarm when flow deviates significantly from normal - on the assumption that a leak would result in greater flow. The problem is that this method would not be particularly useful for small leaks.

#### cswanson

##### New Member
I am trying to understand your situation and how a leak might be different from normal flow. I am trying to imagine a diagram of your system (the piping). I am thinking that there is a control valve that opens and closes - upstream of the control valve is the water supply - downstream are the sprinkler heads.

If there is a place where water is trapped under pressure - and a drop in pressure could indicate a leak then measuring the pressure for a short period of time after valves have close might reveal a leak.

It might be possible to measure the flow rate vs pressure to characterize the system with known good condition of the piping system. You would then monitor the flow vs pressure and signal an alarm when flow deviates significantly from normal - on the assumption that a leak would result in greater flow. The problem is that this method would not be particularly useful for small leaks.

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#### cswanson

##### New Member
As for the slow leak... the water meter is actually very sensitive.. my little triangle spins with only a tiny toilet leak.... so in my next life, I'd just get a sensor that could watch that triangle spin... or something like that.... but that just struck me as kinda crazy.... but if someone has an idea for that ;-)

#### stevez

##### Active Member
Now that I understand the problem a little better I'd offer this comment. Something tells the sprinkler system to be on or off. In the "on" condition the flow rate should be quite different and within a predictable range. The same would be true of the off condition. You could have two parallel flowmeters - a high flow meter and a trickle flow meter. You might add a check valve to the high flow meter that will add a bit of drag. During high flow periods the low flow path would force the flow thru the high flow path and meter - your timer or whatever it is would indicate that high flow is expected and you would then compare normal high flow to what might be an abnormal condition.

During low flow the extra resistance of the high flow path would force what little water moves thru the low flow meter - hopefully at a rate that provides the indication. The timer would be indicating that an "off" condition is expected with corresponding low or no-flow rates. This might be a good application for a PIC or similar device.

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