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.-- afinehowdoyoudo, May 27 2007 Light timer http://www.planetna...ow-light-timer.htmlsimilar to this [afinehowdoyoudo, May 27 2007] someone is working on it http://www.freepate...ne.com/5782578.html [xandram, May 27 2007] [marked-for-deletion] redundant with the 555 idea you linked to. I really don't see the difference.-- ldischler, May 27 2007 [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.-- afinehowdoyoudo, May 27 2007 If you have minor improvements like that, you should annotate the original idea, not add a new one.-- ldischler, May 27 2007 its not better or worse, its a different device-- afinehowdoyoudo, May 29 2007 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.-- jutta, Jun 06 2007 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.-- afinehowdoyoudo, Jun 10 2007 somebody suggested avoiding the OFF-mode 'dribble' by storing energy from ON-mode flow to run the timer during OFF-mode.-- afinehowdoyoudo, Jun 18 2007 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>
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.
-eh, I think about these things too much-- Custardguts, Jun 20 2007 random, halfbakery