I have a 12volt DC 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 way with a capacitor to get a soft closure of the valve? By quick I mean between 0.25 and 0.5 of a second.

The capacitor would need to charge up quickly so that the solenoid would open immediately the current is switched on by the PIR

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That's called 'water hammer.' There are many mechanical remedies available: I know noting of their usefulness.
It seems that this might be easier than calculating what is likely to be a huge capacitor or coming up with a timer circuit

 

I have a 12volt DC 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 way with a capacitor to get a soft closure of the valve? By quick I mean between 0.25 and 0.5 of a second.

The capacitor would need to charge up quickly so that the solenoid would open immediately the current is switched on by the PIR

>

It is hard to say what might be an effective strategy since we do not have any details on the solenoid. If there is a mechanical spring return when the current is removed, then no electrical solution will be effective.

 

use motorized valve instead of solenoid valve

 

What type of solenoid is it? Is it a latching type? But either way, Papabravo is right, I doubt there's an electrical solution to your problem. This because most likely the solenoid's closing action is being helped by the water pressure itself, and that in turn makes it close even faster than when it's activated open.

I'd consider placing a small diaphragm type water pressure tank between the valve and the hose so that it could act as a shock absorber of sorts.

 

Something like this might help.

​

 

I doubt there's an electrical solution to your problem

i just posted one. motorized valves tend to be slower than soleoid valves, often opening/closing is quite long (3-5sec)
https://m.media-amazon.com/images/I/81iA78dQJbL.pdf

https://www.amazon.com/Motorized-El...refix=motorized+valve+12v,aps,141&sr=8-7&th=1

 

A water hammer arrestor such as this should work.

 

What type of solenoid is it? Is it a latching type? But either way, Papabravo is right, I doubt there's an electrical solution to your problem. This because most likely the solenoid's closing action is being helped by the water pressure itself, and that in turn makes it close even faster than when it's activated open.

I'd consider placing a small diaphragm type water pressure tank between the valve and the hose so that it could act as a shock absorber of sorts.

Short of opening it up, I dont know if it has a spring closer, Maybe the water pressure closes it.
Anyway here is a link to the exact same model
Electric Pressure Solenoid Valve Water Air Dc 12v 24v Ac 220v 1/2 Normally Closed Tfw-1s For Solar Water Garden Irrigation - Valves - AliExpress

 

i just posted one. motorized valves tend to be slower than soleoid valves, often opening/closing is quite long (3-5sec)
https://m.media-amazon.com/images/I/81iA78dQJbL.pdf

https://www.amazon.com/Motorized-Electrical-Indicator-U-S-Solid/dp/B06XCQ711H/ref=sr_1_7?crid=1FREYZJMSG0FY&keywords=motorized+valve+12V&qid=1663861500&sprefix=motorized+valve+12v,aps,141&sr=8-7&th=1

True ... that might help. It hadn't occurred to me before because that sort of valve requires an electrical connection. But since we're talking about the TS's sprinkler system, that might not be an issue.

 

i just posted one. motorized valves tend to be slower than soleoid valves, often opening/closing is quite long (3-5sec)
https://m.media-amazon.com/images/I/81iA78dQJbL.pdf

https://www.amazon.com/Motorized-Electrical-Indicator-U-S-Solid/dp/B06XCQ711H/ref=sr_1_7?crid=1FREYZJMSG0FY&keywords=motorized+valve+12V&qid=1663861500&sprefix=motorized+valve+12v,aps,141&sr=8-7&th=1

OTH ... strictly speaking, your proposal is not an electrical solution, but rather a mechanical one ...

 

Is there a way you could have a length of (flexible) hose before the solenoid valve? The idea being that the water pressure will expand that length of hose a bit when the solenoid valve closes. I'm sure there must be a electronic analogy for this - resistors, capacitors, inductors....

 

If you use a typical lawn irrigation solenoid value, they are slow closing, so there is no water hammer.
Might be cheaper than to kludge up something for the valve you have.