Need water flow sensor

Discussion in 'The Projects Forum' started by Rosum2, Mar 16, 2014.

  1. Rosum2

    Thread Starter New Member

    Aug 13, 2013
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    Hi Guys, I'm new here and probably will make mistakes so bear with me.
    Don't you hate it when you come in and see your sprinkler shooting water 20 feet in the air? I have the solution if I can find a simple water flow change sensor!
    Does anyone know where I can find or build a simple water flow sensor that will actuate a switch (closed or open contacts) on flow change? I have the rest of the design finished. All the sensors that I have found lately are much too expensive to use on something like this.
    Any information would be greatly appreciated!
    Thanks
    Rosum2
     
  2. #12

    Expert

    Nov 30, 2010
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    Water softeners have a propeller with a magnet that is sensed by a Hall Effect sensor.
    There's one place to start searching.
     
  3. Metalmann

    Active Member

    Dec 8, 2012
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  4. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    No.. I thought thats what a sprinkler is supposed to do.. :p

    Why don't you explain your project a bit more so we can see why you might need a flow sensor vs just a solenoid or something..
     
  5. inwo

    Well-Known Member

    Nov 7, 2013
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    I use the ones Metalmann linked connected to a plc. They are great, although readings change over time with scale formation.

    A simple timer circuit could respond to high or low pulse period, and trigger a relay.

    I have some that use a reed or ball, and switch. Also self contained programmable ones that use a probe in the flow thru a process fitting.

    The mechanical on/off switches aren't very accurate.
     
  6. burger2227

    Member

    Feb 3, 2014
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    Well what does your solution involve? What do you need the circuit to do with a sensor? Ring an alarm, call you?

    Yeah I would be upset if my sprinkler was shooting 20 feet in the air in my garage... :D
     
  7. wayneh

    Expert

    Sep 9, 2010
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    How about a pressure regulator (no electricity needed)? There are many different types, depending on what you need.
     
  8. #12

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    The problem is that the landscaping guys mow the heads off the sprinklers. You need to detect a high flow rate and use that to shut off the water supply.

    Right?
     
  9. inwo

    Well-Known Member

    Nov 7, 2013
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    There is a commercial device that shuts the water off if a pipe breaks.

    Don't know how it works.

    Must sense a rapid change.
     
  10. #12

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    Rapid change won't work. The lawn guys don't mow the heads off while they are sprinkling.
     
  11. inwo

    Well-Known Member

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    Pressure should work.

    If pressure doesn't build to expected value in xx seconds after valve is powered, system latches off. Or retries after xx minutes.
     
  12. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    coriolis flow meters are the standard in the Chemical industry - no moving parts, no sensors in contact with corrosives, highly accurate.

    Coriolis type Mass Flow Meter
     
  13. wayneh

    Expert

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    Haha, a mag meter for a sprinkler? Love it.

    #12's question is a good one. Is the challenge to detect and react to a missing sprinkler head in a multi-head lawn watering system? That's very different than limiting the max flow from a single sprinkler.
     
  14. Rosum2

    Thread Starter New Member

    Aug 13, 2013
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    Thanks everyone,
    Yes, there are many ways to achieve this end result. I'm hoping for a reasonable price unit that everyone can afford and possibly install themselves.
    I didn't go into details about the project as it is quite a bit more detailed than appears. First, You need to shut the water off immediately! This is done by some sort of relay or digital device controlling the line valve. It has to be triggered by the flow increase. Should it throw a relay or ? it would start again as soon as the clock called for it to sprinkle. This would work. This has to be considered also. My idea is to detect the flow change, trigger a holding device, drop out the line valve, but it goes further than that. On start up the sensor has to be bypassed with a simple time delay. Set the delay for enough time for the pressure to stabilize.
    #12 Yes, that is correct! The higher flow rate would signal the unit to shut down. The rest of the circuit just maintains the operation so the valve won't open until you get to it for service. Yes, it has a warning device I didn't go into. Anything needed can be adapted to warn you.
    Inwo, Yes that will probably work, but, what is the cost? Each valve has to have one to keep all the other valves running as normal.
    The Coriolios sensor would be way too expensive!
    The Regulator mentioned does not stop the flow! It has a small orfice and a meter to show the output. ??
    I am trying to get something simple and very reasonable that anyone can usually afford. A normal property usually has from 2 to ?? number of valves. Consider the cost of one unit for each valve! Could get out of the budget very fast. The installation cost needs to be minimal also.
    Thanks for the ideas,
     
  15. #12

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    It is easy enough to have the lock-out device latch off and stay off until a person does a manual reset.

    In a small system, one large leak can be detected fairly easily. No need to measure every sprinkler head.

    You would need a start up delay if your measuring device was designed to only detect changes. I suggest that this idea is bad. If a sprinkler head is mowed off while the water is not flowing, the leak will stay the same as soon as the start-up delay is over.

    inwo's idea about pressure is viable in this situation, and a pressure sensor might easily be cheaper than a flow rate sensor. One problem lies in the idea that the pump or other source might be entirely capable of supplying the leak with little drop in pressure. Perhaps a restrictor before the pressure sensor. It would have to be sized to the system so it passes enough water with only enough pressure drop to betray a large leak. Perhaps 2 feet of 1/2 inch pipe formed into a 6 inch square on a 10 head system? (just guessing).

    Edit: I'm having difficulty in looking as smart as inwo. He seems to have more experience than I have.
     
  16. wayneh

    Expert

    Sep 9, 2010
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    Don't feel bad. It's taken me this long just to grasp what the heck we're talking about.

    I'm wondering what the ground rules are. I mean, can we think about solutions that involve wiring that passes to every sprinkler head? I think the cost of that alone would be prohibitive unless it is built into the system at the time of installation. But I don't see how any pressure or flow sensor could work unless it is dedicated to a single head, maybe 2.

    There might be a non-electrical device that can close a valve when excess flow is detected, requiring manual reset. That would be a pain if it triggered too easily.
     
  17. #12

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    Trust me :D

    For a lot of systems that are driven by a local pump, when one head is chopped off, the other heads have a massive reduction in pressure. This can be observed by simply driving past a home and noticing that the other sprinkler heads are barely working when a 10 foot jet of water is going straight up.

    A difficult sensing job would happen when the water is supplied by the city with generous sized pipes. For all practical purposes, that would be an infinite supply with low impedance and a restriction would have to be installed as I mentioned in the last paragraph of post #16

    Water circuits can be modeled similar to electrical circuits except the resistors respond to velocity cubed.
     
    Last edited: Mar 19, 2014
  18. wayneh

    Expert

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    Got it. The flow from a severed head is large compared to the normal system flow.

    So a solution that turns off the whole system (or branch) - not just the severed head - is OK?
     
  19. #12

    Expert

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    That's how I would do it, and the OP did mention that cost is a factor.
     
  20. privateer2001

    New Member

    Mar 16, 2014
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    I like puzzles like this and reading the replies. Thanks for posting, guys. This is a real fun forum. Glad I found it. A lot of sharp people on here!

    I'm just trying to understand the system you're designing. So essentially, you have a water system that when running is putting out a certain flow rate in the circuit. So if you knew what the normal flow rate is, you'd have to have a circuit that could distinguish between the normal and increased flow rates. If you had the sensor, possibly remove one head and see how that affects the flow rate and what feedback you'd get at the sensor. And you'd have to have this at the input to the line, not one at every valve, and a solenoid to shut it down until a manual reset could be made. Is that correct?
     
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