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Akin to a light timer with a rotary dial and white or black pegs that are placed at the desired ON/OFF times.
Perhaps with a 48 or 96 hour dial for less frequent watering.
Garden hose in & out, allows full flow in ON mode, with a tiny dribble in OFF mode to power the dial.
Light timer
http://www.planetna...ow-light-timer.html
similar to this [afinehowdoyoudo, May 27 2007]
someone is working on it
http://www.freepate...ne.com/5782578.html
[xandram, May 27 2007]
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Annotation:
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[marked-for-deletion] redundant with the 555 idea you linked to. I really don't see the difference. |
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[ldischler], admittedly this rotary dial timer and the 555 have very similar range of applications. However, this one is self-contained, simple to use, and has a fixed timing cycle. The 555 requires external circuitry and is completely variable. |
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If you have minor improvements like that, you should annotate the original idea, not add a new one. |
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its not better or worse, its a different device |
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The difference (and the reason I'm ignoring ldischler's mfd, but just barely) is that the 555 is a whole hydraulic construct, while this one is just water-powered. So, *this* one I could build by sticking a conventional timer on top of a little wheel - whereas the 555 would be interesting to look at, but would probably take up a pretty big vat and be interesting only as a novelty or teaching toy. |
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thanks [jutta]. Renamed in the hope of distinguishing it from the 555. If I had to choose between the 2, I would keep this one - it's a practical gadget, unlike the complicated 555. |
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somebody suggested avoiding the OFF-mode 'dribble' by storing energy from ON-mode flow to run the timer during OFF-mode. |
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You'll have some challenges here. Flowrate and pressure are interdependent, and neither will ever really be constant in an application like this. Error could easily be in the 25% range or higher. Your mechanism that is powered by the water will be rather sensitive to one or both of these properties <that is if it is truly "water-powered", you could easily make it water-energised, spring-powered or similar. Otherwise you could easily make a system you set for a given volume ie 100 litres, or whatever, this is much easier than a fickle timer> |
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I think I know how to do this accurately, though. It involves a header tank and a float valve, to supply a constant head pressure for the sensitive timer mechanism. |
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-eh, I think about these things too much |
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