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/aquatic-supplies/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.

 

[AdamHorton]

Thanks everybody for all your input, I do appreciate it.

Just to be clear, what I'm looking for isn't something to automatically top off my tank. All I'm looking for is a mechanism to prevent my pump from running dry if for some reason one of my U-tubes loses its siphon and the refugium where my pump is at loses water.

http://www.adamhorton.com/files/flog/newsetup01.jpg

In that picture, it's the tank underneath on the right where I want to install this.

Maybe one of the top-off systems would work when mounted upside-down, but the goal here is not to regulate the water level in the display tank, I have a HOB overflow cup system to do that and I'm happy with it.

The one thing that's missing from this picture for me is a way to hook up the rest of the circuit that dezso posted to the 120V power source safely. Right now the only thing I can do is to stick the wires into the wall socket, which I really don't want to do. Is there such a part that I can plug into the wall and attach wires to?

 

[austinsdad]

I'm thinking the JBJ config I used would work. One sensor was mounted in my sump/fuge so that when it needed water, the pump (plugged into the controller box) in the FW reservoir would engage. The 2nd sensor was also in the FW reservoir which was there to keep the pump from pumping when the reservoir level got too low. What it that config used the second pump where your pump is? The first sensor would be high enuf so that the pump ran all the time.

Just wonderin'.

 

[CaptainAhab]

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.

Isn't that exactly what you're looking for?

 

[AdamHorton]

Isn't that exactly what you're looking for?

Yes, but I already have that part bought. EDIT -- after looking a little more carefully at one of the specific products, I think this is the one you're talking about, right?
http://www.autotopoff.com/products/SS1/
This one could be mounted upside-down in order to shut the pump off when the water level is lower, right?

austinsdad: I'm not sure exactly how that interfaces with the pump. The pump I have can only be turned off/on by unplugging/plugging it from the wall. Will that device support that kind of interface?

 

[ccCapt]

Yes, but I already have that part bought. EDIT -- after looking a little more carefully at one of the specific products, I think this is the one you're talking about, right?
AutoTopoff.com
This one could be mounted upside-down in order to shut the pump off when the water level is lower, right?

You can't mount it upside down. As I previously mentioned.........

Reverse Operation: The controller turns the device off when your water level is low. The device will be powered when your water level is high. To enable this mode of operation, remove the plastic retaining clip that holds the float on and reverse the float so the magnets inside the float are on the bottom.

 

[CaptainAhab]

Ok, so now I'm getting interested...

For clarity, are we saying that the SS1 will work, when operated in reverse mode to shut a pump off that is plugged into it. I assume the unit plugs into the wall and the pump (or whatever) plugs into the unit.

 

[Tank2379]

+ 1 for the JBJ Auto Top off Unit... Works great...

 

[AdamHorton]

I see. The JBJ system will do everything I need and it will do a whole bunch of other stuff that I don't need. The Madison has a mode where it can just monitor my pump, which is what I think I want. Sorry I got confused, Thanks for the help everybody.

 

[CaptainAhab]

I think so too. If you get one, update the thread if possible. If yours works I'l probably do the same thing.

 

[AdamHorton]

I ordered one and it arrived yesterday. I probably won't get a chance to install it until this weekend though, since I need it to be lower than what the mounting bracket will allow. I'll post pictures when it's installed.