For many automatic watering applications such as yard sprinklers or sprouting machines, it would be useful to have a water-powered timing mechanism, to avoid the need for electricity in the system.
The idea is a device which works exactly the same as a 555 timer, except working on water instead of electricity. Voltage -> pressure. Current -> flow rate. Resistor -> needle valve. Capacitor -> accumulator. Implement your specific timing requirement using external 'circuitry' just as with a conventional 555.-- afinehowdoyoudo, May 25 2007 Wikipedia: 555 Timer IC http://en.wikipedia.org/wiki/555_timer_ICTic, toc, octopod. [jutta, May 25 2007] Who is number 555? http://en.wikipedia...i/State_Express_555 [Ling, May 27 2007] Water Timer For Lawn Sprinklers http://www.hardware...hutoff-pW3AUWV.aspxTurns on after a selected pause (say 3 hours), runs for a time (like 10 minutes), then starts over again. Water powered. [Amos Kito, Feb 11 2008] 555 Timer -- Animated http://www.williams...abs.com/480_555.htm [Amos Kito, Feb 11 2008] Clepsydraulic chip form factor?-- lurch, May 25 2007 Should be bakeable, though perhaps not as an exact copy in hydraulic form ... I was just looking at a block diagram of the 555 chip, and I will need to think a while about the hydraulic analogue of a J-K flip-flop and a comparator ... [Ian T], you're not alone, I still get a little twinge of joy when a clock reads 5:55, and stranger still, I have lived the last 9 years in a house numbered 555. (No, that wasn't the reason I bought it !)-- batou, May 25 2007 If we're talking about fondly-remembered nostalgic chip numbers, can we please have a moment's silence for 741?-- MaxwellBuchanan, May 25 2007 //Current -> flow rate// So you're always dribbling water?-- ldischler, May 25 2007 Who, me?-- MaxwellBuchanan, May 25 2007 I'd bun a hydraulic 4:20.-- nuclear hobo, May 25 2007 Factoid: Subaru were sponsored by 555, once, and later named one version 22B, which is hex for 555.-- Ling, May 27 2007 Actually, the 555 timer was so good that it eventually achieved consciousness in 1992 and, a year later, decided that it would like to sponsor rally cars.
Less likely, the 555 on the Rally Subaru Impreza is the name of their sponsor. State Express 555 is a brand of Cigarettes made by British American Tobacco.-- Ling, May 27 2007 I always thought that Subaru used '555' because it is 'Go, go, go' in Japanese.-- neutrinos_shadow, May 27 2007 pneumatic control circuits using cascade logic and valves have been around for donkey's years.
The requirements on accumulators, constant supply pressure/flowrate and the sensitivity given zero volumetric change would make this system extremely hard to commission, given when independent circuits engage, system flowrate and thus pressure would drop, affecting the entire control system. You would need some pretty good referencing points to keep the system stable.
Other than that, you might be onto something here, although similar applications in hydralic cascade control systems make this, of not baked, at least pre-warmed.
Oh, lastly, I'm a wee bit rusty on the modelling side, but given your resistor=needle valve comment, I think maybe you might end up having to swap around pressure and flowrate in your model for some of the maths to work.
[+] for thinking outside the box-- Custardguts, May 28 2007 //Sponsored by a number? What does that mean?// see Sesame Street for further explanation.-- xaviergisz, May 28 2007 It's the road leading to play school.-- Custardguts, Feb 11 2008 Acutally in order for the device to turn on and off automatically, you would need two 555 timers...one for the on-delay and one for the off-delay. Fortunately, for all wateriing mankind, there is a dual 555 timer called a 556. If you will look up 556 and 555 timer applications, especially via Forrest Mims web site, you will find almost exactly what you are looking for....shematically, of course. However, nice things like water proof case, relay controlled valves etc will be up to your personal enginuity. This is not a difficult project...just about any amature electronics hobbiest should be able to cobble one together in a few hours and a visit or two to Radioshack.
Of course, getting the electronic timers to run on water instead of a low cost 9 volt battery is another challenge...
Here's a fresh hot bun on me...good idea.-- Blisterbob, Feb 11 2008 A toilet tank is a common type of water “accumulator”. It’s not a complete analogy for the idea, except for emptying and filling on each cycle. That tank's “monostable” (one cycle for each input). If you want it to be on an automatic loop, you will run “astable” -- on and off at a steady rhythm. Yes, you will need two "hydraulic 555" oscillators, as [BlisterBob] said, for this idea to work. Otherwise, if it turns on every 24 hours, it runs for 24 hours before the valve closes.-- Amos Kito, Feb 11 2008 Good point, Amos. Suppsoe one had a very slow filling tank, that once the float triggered, it initiated a watering sysle that then emptied the tank via a venturi.....when the tanks finally emptied, another (off) float triggered the stop and the tank began to slow fill again restarting the entire process. I actually think this thing could work quite reliably...watch out in very cold weather, of course. Adjustment of the times would be by way of the filling valve and the emptying valve at the venturi.-- Blisterbob, Feb 11 2008 [Blisterbob], that's pretty much how the 555 timer works, by charging and discharging a capacitor, and monitoring the voltage levels.-- Ling, Feb 12 2008 random, halfbakery