From what I understand, or all Ive been told, a selenoid is a type of valve.... But it must be special in some way. I really doubt its a monster that grew out of selenium...

Help me out as much as you can yoze. Is it like an electrically controlled valve, instead of opened by pressure etc?

A solenoid is a valve that is opened by a coil (electromagnet). this valve uses the coil to produce an electromagnetic field that actuates a plunger. this inturn opens or closes the valve.
lates
james

Yep its just like a relay in that you energize a coil (battery and ground) and it opens the plunger to allow fluid/gas etc.. to flow

Ok so then, a switch can open a selenoid? Like on/off makes it open/close?

Also, how do I buy one? I just need any selenoid. Do I say "selenoid please" or do I need a specific application?

yes you can wire it to a switch
and there are thousands of diff solenoids,
what are you trying to do and maybe we can help

Uhm....fluid or gas would need to be specified. Also you'll probably want to know the diameter you're looking for...as in input output tubes. Flowrate when open...uhm...will it be an open/close only or variable rate control. Those are the ones I can think of.

Trying build your own fake bov? I'm not being a dick...if you do it I wanna see how. I don't wanna make one, I'm just a gadget freak and i'm interested. I think mechanically it would be far cooler than electronically.

Actually, the idea came out of a diy i read on how to build a fake bov.

Before I explain it for the fake BOV, ill tell you what Im using it for. I have a 200g saltwater REEF tank. Now thats different than just a saltwater tank. At 200g, the tank needs to be 'turned around' (all water pumped in and out) nearly 10X. THat means I need to push water at a rate of 200X10 = 2000gph. Which I do. But, its unnatural for a reef to feel water current flow the same way non stop. So I have a 100G extra tank mounted above the reef, filled with water. A pipe goes in the bottom of that tank, so the water in it just spills down to the first tank at a high rate fo speed.

ANyways, instead of manually turning a valve to let the water spill down and shift around the current of the tank for a few mintues, Id rather click a switch. I know theres a lot of work to be done instead of just adding a selenoid, but thats the basic jist of it.

Anyways, the place I learned or got the idea to use a selenoid was I was reading about making a fake BOV. Way to much involved for me. But it said to hook a compressor, like a A/C compressor up to a belt in your car so it can compress air. Then have it go to a selenoid and whenever you want you hit a switch and the selenoid opens. Im not going to get a whole new dang compressor to make something fake.

Anywas, I have a question. The selenoid I bought, so dumb old ford thing for $5, doesnt look...... right. How many things should the selenoid have it? This has these 2 metal posts....... And then two other posts marked S and I. Huh? WHeres water or gas/fuel run through? Did I get the wrong selenoid? Maybe I need to unscrew some things, it could be all put together or something... Are some selenoids not for fluid or air?

Ok I messed around tonight with the fake BOV idea which you may have read in my general2gnt post.

Anyways, with the air comp hooked up to the belt I can get it to probably work up to 200min psi maybe up to 300psi. So itll all be trapped in there. How can I hit a switch to make it all hiss out? like open a valve? Is that where the selenoid comes in? Anyone know a specific selenoid I should get. I fyou know any other way, let me know.