Float switch auto pump turn-off

[AdamHorton]

I know this is super-paranoid, but I'm kind of surprised that I'm (seemingly) the only person to want to try this:

In my refugium/sump where my sump pump is, I want to install a float switch that will turn the pump off when the water level gets too low. I've bought a float switch already which can either close or open a circuit when I want the pump off.

Unfortunately, the only way I have of turning the pump on and off is by plugging/unplugging it. What I need is something that I can plug into the wall, and then plug my pump into that will take the input from my float switch turn on/off the pump. I went to Radio Shack and the guy there sold me some kind of "relay" and a power supply for it. I have a master's degree in electrical and computer engineering and I haven't the slightest idea what he wanted me to do with it, and I'm kind of worried about doing it that way anyways because I don't want to fry my switch with too much current.

Has anyone ever dealt with this before, or might have some help? Thanks,

[InfernoST]

I would be careful with what kind of voltage you send through that switch, do you know the specifications on the switch and are the switch connections out in the open or protected? Usually it's a microswitch with a low current capacity and would probably burn out in short order, the only way around the capacity limitations of the microswitch is to drive a relay with a high current capacity contacts and low voltage dc coil which would require you to get a transformer to step your house voltage down to drive the relay then run the hot leg through the relay contact to drive the pump. Almost forgot, the relay needed would also have to be capable of handling an inductive load.

[dezso]

Ohhhh

Master in this field and "I haven't the slightest idea what he wanted me to do"....

Maybe this will help.

Check your relay and match the voltage on the left side.

[dezso]

Also currently working on a fancy looking controller, it might not be commercial grade, it will have many custom function.

This is just a sneak peek...

[InfernoST]

That's exactly it, However if your relay is normally de-energized you want to use NC contacts not NO.

[AdamHorton]

I can mount the float switch upside down to have NC or NO, whichever is desired, but it's an SPST switch (two leads), not SPDT so I doubt that matters.

I have a 12V transformer for the relay. That diagram really helps out, you must be a genius. What is a safe way to get the 120VAC connected to the pump and the relay? Basically, something I can plug in to the battery backup I have and attach my wires to that won't leave too much exposed. I haven't seen anything like that (at least that I can recall).

To be fair, my focus was mainly on software, but you would think they would teach me what a relay was though... I hated all that EE stuff

[dezso]

You might want to buy a relay socket or solder the wires to the relay pins, also you can buy a small PCB from radio-shack and solder it there.

Brand New Relay and Socket for Heavy Load Motor Control on eBay.ca (item 330363359638 end time 25-Nov-09 23:20:14 EST)

[dezso]

Solid state relay also would work very well.

New in Box Solid State Relay SSR 24-480V AC, 25A on eBay.ca (item 370280789239 end time 27-Oct-09 16:28:18 EDT)

[austinsdad]

The JBJ Auto Top Off (ATO) sells for nearly $80 bucks. It has 2 floats to use in 3 different configs I thinnk. One stops the top off pump when the level in the FW reservoir gets low. Wonder if it could be used for your needs. But of course, what's the fun in that when you can build yur own, huh?

http://www.premiumaquatics.com/aquat...s/JBJ-ATO.html

[ccCapt]

Check out www.autotopoff.com. They have exactly what you are looking for. They use a Madison M8000 float switch and reversed the magnets so it sends the signal to the relay to turn off the power when the water level drops below the switch.