The Snail Paced Drip Of The Solenoid

12v Magnetic Solenoid Valve

Whilst looking at options for making an Arduino powered watering system, I brought a “12v Electric Solenoid Valve Magnetic DC N/C Water Air Inlet Flow Switch ½”, attached it to a bucket of water and plugged it into a 12v battery. Immediately I heard a quick clocking noise as the magnet worked and water started flowing through. Slowly.

Very, very very slowly.

Drip, drip, drip. It became obvious that it would take a long time to water the greenhouse plants using this as we could be using anywhere up to 2 litres a day. This would drain energy the whole time it was activated. Whilst not a viable option for the project we decided to take it apart and find out how it works.

First came off the four screws at the top and then the white plastic that looked like a spinning top. Inside the long pole was a spring and a metal piece known as an “armature”. When current is passed into the solenoid, the core works to close the air gap between itself and the armature pulling it towards itself. This leaves a small opening at the “tap” allowing water to pass through. It would appear to be heavily reliant on pressure as added pressure made the flow marginally quicker but this was limited by the spring which is used to push the armature back in place post energizing.

Potentially what we could have done is cut some of the spring to allow more pressure when the magnet is activated, drawing the armature closer in. Again this change would be marginal whilst risking the possibility of not being able to seal the water gap when power is no longer supplied.

It would appear a servo would be the next thing to look at.