I am interested in making a flow switch similar to the ones that are used in fire suppression system for my WC computer the device is called a flow sensor and it triggers the alarm if a sprinkler head is activated it works by having a small paddle that hangs in the flow line then when water flows the alam is tripped I would like to do just the opposite I want it to work with a lack of flow, I am not really interested in setting off a alarm but rather I would like the switch to trigger a relay that would power off the computer I can see this in my head bu unfortunately I do not have the skillz to pull this off maybe with some of your help I can make this little savior come to life If a item like this is already available please let me know.
Use a 555 IC timer wired as a Missing Pulse detector. The paddle could be seperated, by inserting an infrared emitter and sensor pair to detect if the paddle is moving. The 555 IC timer's timing cycle will be continually resetted by incoming pulses; if there is a long enough duration where there are no pulses, a pulse out will come from the timer. From this website scroll down until you get to the "example circuits" section, the "Missing Pulse Detector" is the last one (Fig 10a).
Take some PVC, put your paddle or whatever in it, glue this to the tip of a switch. Use an inverter gate, or have your switch off when its pulled?
you probably want a switch of-delay.If the pc switches off at the moment it looses flow you wouldn't be able to power it on. (no flow at startup)
There used be a guide to build one on this website wernt they? but i havent seen sinced they changed it along with a few other guides which has disapeared.
