OpenSprinkler Forums OpenSprinkler Unified Firmware Unconnected cable sending flow data (!)

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    Hello, I have an issue with my flow sensor.
    The unit has been working fine for one year or so, set at 0,01 L/pulse; then it started showing an uncommanded 10.00 L/min flow even when water was actually not flowing.
    Suspecting a faulty flow sensor, I disconnected the flow sensor from its end of the 15 meter cable running from the Opensprinkler unit to the flow sensor, leaving the other end of the cable connected to the Opensprinkler unit; however, the 10.00 L/min flow remained.
    Suspecting then a faulty Opensprinkler unit, I disconnected the other end of the 15 meter cable from the unit, and the flow stopped immediately.

    It looks then like the unconnected cable is sending pulse to the Opensprinkler! The rate is 10.00 L/min at 0,01 L/pulse, so 1.000 pulse/min. This does not even match with the AC frequency running the valves (which anyway are normally closed and unpowered most of the time), as 1.000 pulse/min is 17 Hz, and the AC is 50 Hz.

    What the hell is going on?

    Thanks a lot!



    Is your sensor positive or negative pulse? If you have a bad sensor and leave the sensor wire “floating” all sorts of wierd things can happen. The wire acts as an antenna and once the voltage on the wire reaches a high enough peak it will trigger a signal. The wire can get interference from just about anything, like wireless routers, your TV, the microwave, or even radio stations. So trying to tie the phantom pulse to something can be very difficult, however, it is likely you have a bad sensor and replacing it will remedy the problem.

    If it’s a positive pulse setup don’t ever leave the wire hanging in the air with nothing attached, a large enough charge can build on the wire and damage the port. This is why cable TV ports left open will have terminators, a basic load, on them.

    If you have a negative pulse setup, watch for bad or disconnected grounds. A partial ground fault can cause spurious signals. Leaving the wire hanging in this setup usually results in bad or no data, but can damage the port sending the signal down the wire by acting as a short circuit. Odds are this is the type of sensor you have and it is either bad or the wire going to it is damaged or improperly connected.

    Short answer, you most likely need to replace your flow sensor and the problem will go away. Hope that helps a bit.



    I want to echo SharnHarte that perhaps you are getting some sort of signal interference. The sensor uses ‘interrupts’ to detect flow pulses. If the wire is sending pulses unexpectedly due to signal interference, that could be interpreted as flow pulses.

    When you leave only one cable in the sensor, you should try both ports of the rain sensor: one of the port is circuit ground (I think it’s the one on the right). I assume if the wire is left in that port it shouldn’t have any interference since that’s the circuit ground. You may have left the wire in the other port (which feeds into a microcontroller pin) and that is prone to interference from ‘floating’ signals.



    Thanks everyone!
    I believe it’s really an interference, as is still keeps sending the signal even with the flow sensor disconnected!
    How can I get rid of it?


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OpenSprinkler Forums OpenSprinkler Unified Firmware Unconnected cable sending flow data (!)