de-gradation of latching solenoids?

[schnell]

Hi,

We are thinking of using latching solenoids to divert water in domestic water pipes.

We see on datasheet that it takes one Watt of electrical power for 20ms to latch the solenoid.

-but after a few years of use, will it take more time to latch....eg , 1 Watt for 40ms?

here is the electrical part of the datasheet

http://i53.tinypic.com/jg5v1i.jpg

 

[danw2]

I missed the part about the increased power over time, but wonder whether it could be the effect of dirt, grime, hard water deposits, whatever that takes more power to activate the solenoid compared to when it's brand new out of the box.

 

[MikeHalloran]

Years? Never had one last that long.

I don't know if it's mechanical wear products jamming the mechanism or interfering with the magnetic circuit, or aging of the permanent magnets with the magnetic circuit open, or what, but they've never lasted for me, and their lifetimes were short enough that I had no interest in trying to improve them.

Always ended up with two-current drivers and regular solenoids; high current pull-in, low current hold-in.

Maybe they've improved. Maybe you'll get lucky. YMMV.



Mike Halloran
Pembroke Pines, FL, USA

 

[israelkk]

If you are talking about irrigation valves latch solenoid types, they are really low cost products. They usually cost ~$1.5 to $2 to manufacture. They are not robustly designed. The electromagnetic force of solenoid has no margin for added friction or added spring force due to tolerances, dirt, etc. If the return spring is a little stronger the electromagnetic pull force due to coil will not be enough or the permanent magnet circuit force will not hold the plunger when the current is removed. On the other hand if the spring force is a little lower the plunger will stay stick due to the permanent magnet. When such solenoids are designed for military or aerospace the pull magnetic force should be 1.5 to 2 times stronger than the spring. While in the commercial solenoids I encountered I believe the factor is even less than 1.1.