OpenSprinkler Forums Hardware Questions OpenSprinkler SOLVED: Support for Hunter flow sensor

This topic contains 9 replies, has 3 voices, and was last updated by  951calguy 7 hours, 12 minutes ago.

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  • #46451

    richardgedwards
    Participant

    I have a flow sensor that works with a 4-20 mA current loop. Is this compatible with OpenSprinkler? If it is not, is there a way to adapt a 4-20 mA signal to be compatible with OpenSprinkler?

    #46703

    Ray
    Keymaster

    Do you have a link to the flow sensor? Does it require constant current, or is it that it outputs current that’s proportional to the flow rate? If it’s the latter, there isn’t an easy way to make it work with OpenSprinkler — because in that case it’s outputting an analog signal, which needs to be fed into an analog pin. That requires changing the firmware to support such sensors. In contrast, the supported flow sensors work by sending pulses, and the frequency is proportional to the flow rate.

    • This reply was modified 2 months, 1 week ago by  Ray.
    #46769

    richardgedwards
    Participant

    Hi Ray,

    It is a Hunter flow sensor. I bought the sensor without the control module. Hunter does not seem to be to willing to share how their sensor works, but I did some experimenting and biased the two wires out of the sensor with various voltages and measured the current. As the paddle rotates the current changes from a low state (~4 mA) to a high state (~20 mA). Here are the actual measured results.

    One way I thought of solving the problem is to drive a reed relay with the 4-20 mA current, that way I could isolate the sensor from OpenSprinkler and use a separate power supply to power the flow sensor. However I am having a bit of trouble converting the current to a usable voltage to drive the relay. I was wondering if this approach seemed reasonable or if there was an easier and more elegant way the community could suggest that I am overlooking. Unfortunately, the voltage across a 250 ohm resistor does not work since it converts the 4-20 mA to 1-5 VDC and the 1 VDC is above the threshold of the turnoff voltage of the relay. Maybe what I am really after is a circuit to convert 4-20 mA to 0-5V to drive the relay powered by a 12 or 24 volt power supply. I have a separate power supply that converts 24 VAC to 5,12 or 24 VDC.

    #46848

    richardgedwards
    Participant

    I found an easy, inexpensive way to make the Hunter flow sensor compatible with opensprinkler, even though it may not be optimal. I found this board on the ebay:24V 4-20mA Current Detection Limit Value Control Switch Alarm Converter Module. The reason it is not optimal is that the relay should be a reed relay for reliability. I biased the sensor with 12 vdc with a separate 24vac to dc converter. I’ll attach a picture of the setup. I’m interested if anyone has a better approach.

    #46857

    richardgedwards
    Participant

    I solved the reliability problem by removing the power relay from the board and soldered in a reed relay. Here is a link to the relay I used.

    Link to reed relay

    Overall I am satisfied with the hardware setup now. I like that the flow sensor uses a current loop for noise immunity. I also like that this setup isolates the flow sensor from the controller through the reed relay.

    #47213

    Ray
    Keymaster

    OK that’s good to hear, and thanks for the efforts to reverse engineer how this sensor works, and share your knowledge with us!

    #47389

    951calguy
    Participant

    Could you please elaborate on how you are making that sensor work with OS? maybe a step by step? I have been trying to use data industrial or cst sensors unsuccessfully.

    Thank you.

    #47476

    951calguy
    Participant

    Could anyone help with this? I am really interested on getting a way to use either hunter, cst, or data industrial flow sensors.

    #47480

    richardgedwards
    Participant

    Hi 951calguy,

    I am not familiar with the cst or data industrial flow sensors. Could you possibly post a link or a datasheet? As far as the Hunter flow sensor there was not a lot of information out there about it so I had to run some tests to see how it exactly worked as I mentioned in a previous post. This would be the first step to try and figure out the interface of how it works and try and make it compatible with open sprinkler. In the end you need to interface you flow sensor to be compatible with the open sprinkler interface as described below.

    Flow Sensor: when using a flow sensor, the controller will detect flow sensor pulses,
    display real-time flow rate at the footer, and log the flow volume at the end of each
    program run. Only dry-contact, 2-wire flow sensors are supported: these sensors are
    essentially flow-activated switches which close and open repeatedly as water flows
    through the meter. They do not need power, and typically come with 2 wires. Insert the
    two wires to the sensor terminal on OpenSprinkler (there is no polarity). Then set the
    flow pulse rate, which you can find out in your flow sensor’s datasheet, and is used to
    convert the pulse count to actual volume. Flow sensors with 3 wires usually require
    power and thus need some modifications before they can be used with OpenSprinkler

    In order to make the Hunter flow sensor work you need three items.

    1. The flow sensor itself.
    2. Electronics that converts flow sensor interface to open sprinkler interface, open close contact
    3. A power supply to drive the electronics in step 2.

    Maybe you can review the previous posts and ask more specific questions where you need help.

    #47481

    951calguy
    Participant
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OpenSprinkler Forums Hardware Questions OpenSprinkler SOLVED: Support for Hunter flow sensor