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Forum Index : Other Stuff : F&P water solenoid - Volts?
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| domwild Guru  Joined: 16/12/2005 Location: AustraliaPosts: 873 |
Hi, A relative had a good idea how to water his plants inside the house while he was away, namely a water tank on a stand, a 24hr timer, valve solenoid and drippers. The timer switched on a transformer for the valve to start/stop the watering. Question: This idea might just work with the hot/cold water inlet from the F&P, but I need to know the voltage and AC or DC. The two inlets are two BSP threads, the outlet is just a hole to drip into the basket and hopefully a proper barb can be glued to it. Any idea? I do not have a working F&P to test the voltage. Taxation as a means of achieving prosperity is like a man standing inside a bucket trying to lift himself up. Winston Churchill |
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Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
By memory they are a 12VDC coil on the solenoid. The problem you will have is not enough pressure to open the diaphram and it will only drip through the bleed hole, also water flow is normally required to help cool the coils, im doubtful your idea will work. Some time back you could buy a battery powered single garden tap irrigation timer/controler, these had a small gear drive motor in them that open/closed a valve, (not solenoid) and would work well for your application. Im nor sure if you can still get them, but a trip to Bunnings might be worth a look. Something like these below, although im not sure if the first one is a motor drive or solenoid. http://www.ebay.com.au/itm/New-Hotsell-helpful-Electronic-LC D-Water-Timer-Garden-Irrigation-Program-B98B/231080040491?_t rksid=p2045573.m2042&_trkparms=aid%3D111000%26algo%3DREC.CUR RENT%26ao%3D1%26asc%3D27%26meid%3D2546316536846855833%26pid% 3D100033%26prg%3D1011%26rk%3D2%26rkt%3D4%26sd%3D400587276321 %26#ht_6873wt_1012 http://www.ebay.com.au/itm/1-OUTLET-TAP-TIMER-Irrigation-Con troller-/221295676464?pt=LH_DefaultDomain_15&hash=item338640 0c30#ht_2066wt_932 Pete. Sometimes it just works |
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| Georgen Guru Joined: 13/09/2011 Location: AustraliaPosts: 462 |
Toilet flushing system can be quite a low cost solution for indefinitely watering plants. Yes it can be fiddly, but cistern water level is quite constant. Couple of working systems I managed to see myself. One was one very simple: Wick dipped into cistern from African violet supplied all the water plant needed. Pot was there permanently, so holiday or not, it worked. Second one was bit more complicated. Tube from cistern was connected to dish in which plants stood and water level fluctuated about an inch before cistern topped itself up. George |
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| domwild Guru Joined: 16/12/2005 Location: AustraliaPosts: 873 |
Thanks for help. If it is 12VDC, then I have a transformer which is suitable as another valve wanted 24VAC. You are correct, it would need a head of water to push it through the valve and drippers, so my idea of a two-meter head might be insufficient. Outside trees need to be watered, but the wick/tray idea is ideal for indoor plants. Needs to be on the cheap side as the 28s, a declared pest, are getting all the fruit and berries anyway! They ate the single cherry on our $40 tree, which I had leered at with unbridled lust since it got more and more reddish, so I also have to get nets and apply "Rule 0.22" when I am there every four to six weeks. The foresters in large blue gum plantations have taped the alarm cry of those pests and play it on top of the four-wheel drive and then shoot when they fly in to investigate. They snip off the tops of young trees, which means forks which means that anything less than five meters gets thrown away and becomes a fire danger! Tons and tons of it! Taxation as a means of achieving prosperity is like a man standing inside a bucket trying to lift himself up. Winston Churchill |
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| domwild Guru Joined: 16/12/2005 Location: AustraliaPosts: 873 |
12VDC causes a click and looks like the correct voltage. Polarity has to be worked out as it might pull the plunger in the wrong direction. Battery-driven motor looks like a good idea rather than running a cable through the garden. Taxation as a means of achieving prosperity is like a man standing inside a bucket trying to lift himself up. Winston Churchill |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
If you have your heart set on 12 volts dc, how about those small solenoid valves used in automotive applications for engine emissions systems. These normally route vacuum or atmospheric pressure for various purposes, and a drip system does not need to have massive flow. Cheers, Tony. |
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| Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
When will you guys realize that a solenoid valve requires a high enough differential pressure across the diaphragm to open the valve. Gravity feed pressure won't cut it, it simply won't work other than a small trickle via the bleed hole the coil activated piston will provide. Its pushing sh*t up hill trying to design a solenoid valve system to work under low pressure flow systems. You will need a minimum of 30psi or greater to even consider a solenoid valve to operate. Remember its pressure over a square area of the diaphragm that opens a solenoid, so a bees dick of pressure won't work. Hence why i suggested the motor drive valves in the first place. Pete. Sometimes it just works |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
The solenoid valves used in gas appliances to control natural gas flow are made to function at working pressures of only four inches of water (about.01 psi) and have large flow areas and negligible pressure drop when open. Solenoid valves DESIGNED to work at very high pressures certainly do need high pressures to function properly, but not all solenoid valves work that way. There are a vast number of different types of solenoid valves out there designed to do some very different jobs. Cheers, Tony. |
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| Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
Very true, but this thread was about using F&P solenoids or perhaps irrigation type solenoid. Also you would not use a gas solenoid for water flow, or a car fuel solenoid for water, etc. It would be a failure waiting to happen. Pete. Sometimes it just works |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
I suppose it depends if the type of plastics they use in automotive air solenoids rusts. Cheers, Tony. |
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| domwild Guru Joined: 16/12/2005 Location: AustraliaPosts: 873 |
The solenoid lifts the valve open, so why would it need pressure? But a battery driven motorised system looks like a better system with less head loss. Taxation as a means of achieving prosperity is like a man standing inside a bucket trying to lift himself up. Winston Churchill |
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| Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
A solenoid valve has several parts, the coil only controls a small piston that opens/closes a bleed hole in the diaphragm. The diaphragm is a rubber disc that actually controls the water flow (Not the coil), pressure is required to lift the diaphragm allowing water to bypass under it. A solenoid works by pressure applied to both sides of the diaphragm, the inlet side (bottom) has a smaller area exposed to the water pressure than the top side, this gives a differential of pressure across the diaphragm, with a greater force on the top than on the bottom side, this closes the valve by squashing the diaphragm down. The coil piston opens a little bleed hole on the top side which bleeds water from the top side into the outlet, now there is a greater force on the bottom of the diaphragm which pushes it upwards allowing water to flow to the outlet. When you switch the coil off the piston drops back down closing the bleed hole and the pressure builds on the top side squashing the diaphragm back down to stop the flow. As you see pressure is required to operate the valve correctly, as without enough pressure the diaphragm wont move and you will only get a small trickle of water through the bleed hole. There is often a weak spring on the top side of the diaphragm that adds a little positive pressure to ensure the diaphragm closes when pressure is equal on both sides of the diaphragm. I have seen this common misunderstanding of how a solenoid valve works often, with people trying to use them on a low pressure system, like a rainwater tank or gravity fed reservoirs like often used in hydroponics. Pete. Sometimes it just works |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Pete, What you say is certainly true of all common high pressure and high flow solenoid valves used with mains pressure water. And just as you say, some minimal working head pressure is absolutely essential for the small pilot valve to be able to open the much larger flow area main valve. But they are not the only types of solenoid valves. Automotive fuel injectors certainly do not work that way, and neither do many small flow or very low pressure direct acting solenoid valves. Many just have a small plunger and a spring which operates directly. Cheap, simple, and effective and perfectly suited to gravity feed drip watering. Most of these have plastic bodies and stainless steel springs which makes them compatible with many fluids, including water. Cheers, Tony. |
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| domwild Guru Joined: 16/12/2005 Location: AustraliaPosts: 873 |
I really should wear glasses and look more carefully; old age is a terrible thing, try to avoid it! The solenoid body has a "24V" stamped on it, so it must be 24VAC. I will have a look what Bunnings has to offer with its battery-driven models. Can also check the flow rate with the F&P valve and the 12VDC one in a trickle system. Taxation as a means of achieving prosperity is like a man standing inside a bucket trying to lift himself up. Winston Churchill |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Don't overlook the automotive stuff. Every car these days has at least a couple of these "emissions solenoid valves" usually mounted on the firewall. All shapes and sizes, normally open, normally closed, and changeover types are available. This is the type of thing:  Cheers, Tony. |
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| domwild Guru Joined: 16/12/2005 Location: AustraliaPosts: 873 |
Thanks. Looked at Bunnings and for about $30 or more all sorts of battery-driven models are available. Need 2 AAA batts. They will probably suffer a smaller head loss if they are motor driven. Now all I need is a big tank. Taxation as a means of achieving prosperity is like a man standing inside a bucket trying to lift himself up. Winston Churchill |
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