Pool water level stabelizer

[rybitski]

Electrodes will sense a closed circuit the instant water bridges them, and any wave (even tiny ones) could potentially cause opening and closing at ridiculous rates

This is true, but it is also true for the reed switch. ( I like the reed switch idea)

Let's complicate things... Now we need some kind of circuit that doesn't turn on the relay unless the switch is closed for more than 5 seconds (or something like that).

[rybitski]

How about a timer circuit that when energizes times 5 seconds then sends the signal to the relay. After the circuit is de energized the timer resets and waits to repeat the process...
I don't know of a way to do it, but it is a theory...

[ante]

There is no big problem using electrodes to control a relay. Just like an automatic bailout pump for a daycruiser a timer closes the relay 5 minutes or so after continuous contact between the electrodes, this will cure the problem. No rattling relays! But if using AC the electrodes can be partly submerged at any given time and the capacitance between them indicates the level.
If you like to avoid electronics, try the simple way with a reed switch. To get the pump start-to-stop range as wide as possible try to find a strong magnet, cannibalize one from an old hard drive they are very strong.

[rybitski]

It is not that I like to avoid elesctronics... but why complicate matters?

[rybitski]

Show us how you would build it, Ante. Please. ;D

[ante]

Hi Chris,

Ok, the easy way: reed switch and magnet! This is very close to your original idea! Attach a magnet to a cylindrical float (plastic); put the float inside a tube (also plastic) which has an inner diameter just to fit the float. Close the bottom end of the pipe and leave the top end open and above the surface at all times. Attach a reed switch on the outside of the tube; make a small bracket which might be kept in place with a stainless steel house clamp for easy adjustment. Drill some small holes along the pipe (size and distance of the holes depends on the size of everything else) this will have a dampening effect on the float when you dive into the water or playing with your rubber duck. ;D

[rybitski]

What would be some appliances that have reed switches?
I found one in an old mac printer, but it was a normally closed reed switch.

P.S.
I'm a scavenger. ;)

[ante]

Well, reed switches can be hard to find also for dumpster divers! Try older copiers and faxes even in some old printer or buy one, they are not very expensive.  ;)

[rybitski]

ah, I might have to buy one... I dunno I feel more acomplished (and rewarded) if I hind it in something someone was throwing away...

[ante]

Yes, I know what you mean. If you Google ´reed relay´ you get an idea of how such a relay looks, there are many shapes and sizes. Sometimes you can pull out the glass element from this type of relay and use it for other purposes. If you find mercury relays or mercury wetted relays, just leave them and do not tamper with them! ;)