Have solenoid valve close gently

[Bazza]

I have a 12volt solenoid that opens and closes a water valve. It opens the valve instantaneously which is great. I have it coupled up to a hose and sprinkler activated by a 12v PIR and use it as a fox/cat deterrent.

The problem is it that the valve instantaneously which causes a massive shock wave back down the hose which stresses all the other water pipe connections and blows the hose off the connector.

Is there any simple (and cheap) way to get a soft closure of the valve? Can it be done with an electric gizmo or any other way?

[Tim+]

Put the solenoid at the tap end rather than the nozzle end?

Tim

[Clive Arthur]

I spent some time many years ago trying to make a solenoid valve operate slowly using PWM. Complete failure - once you get past a certain point, wham.

I'd look at a small pressure vessel, eg eBay 324596667784, just the first one I came across.

[alan_m]

Would an inline one way valve work? With the valve held to the hose with jubilee clips.

something similar to

but of the correct bore for the hose.

[Andy Burns]

fit a surge arrester, e.g.

[John Rumm]

Prolly easier to just fit a water hammer shock arrester in the pipe to soak up the percussive effect.

[Brian Gaff]

Normally solenoids work that way, to try to make them close and open slowly you are in effect looking for a tap. I remember a tape deck whose solenoids were noisy, but try to put a ramp waveform in too make them slower and sometimes they got stuck or varied in their delays, which was hardly a good thing when editing. I don't think I've ever heard of a soft solenoid, as I say, you need some kind of rotating valve system. Brian

[Dave Plowman (News]

Is it 12v DC? If so, a large capacitor across it will slow it down.

[Clive Arthur]

No, that will delay it, but it will still snap shut. I have the T-Shirt.

[Bazza]

Yes, it's 12volt DC

[Harry Bloomfield Esq]

Cats and foxes would hear the water filling the hose, and be long gone.

[Fredxx]

What size did you have in mind? Last one I saw was 300mA current. 1s at say 6v drop and 300mA would be 50,000uF

I think a 3ft vertical pipe full of air nearby would be a better bed. Some solenoid valves are designed to snap shut, so any slowing down of solenoid operation might have minimal effect.

[Chris J Dixon]

And that is a bad outcome?

Chris

[Andy Burns]

How would that be classed as "not working"?

[Harry Bloomfield Esq]

It would not have the desired effect for long - quickly they would learn that the noise meant a spray of water soon, so move out the way and carry on. An instant spray, would be too late to avoid.

[Joe]

Wouldn't the hose stay full of water?

[alan_m]

Over the years I have tried various cat deterrents - none work.

Things that cat don't like to smell -they just mask it with cat shit.

PIR triggered water sprayer - they get used to it and just side step the jet.

Ultrasonic sounders - it frightens them the first time but then they just ignore it.

The only thing that works is cat food in antifreeze.

[The Natural Philosopher]

What you need is a canister of air to damp the hydraulic shock aka 'pressure vessel' when i'ts a part of central heating

[Rod Speed]

Surely it must be possible to make it impossible to sidestep or make the spray random so it can't be sidestepped.

But that sees Adam execute you, very unpleasantly.

[Rob Morley]

Put a big capacitor across the solenoid?