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Discussion Starter · #1 ·
Does anybody know how to wire a latching with fail-safe switch on an auto top off connected to a low voltage relay. I can get 3 float sensors off of ebay, and a low voltage relay with 12vdc adapter. I just don't have a clue how to wire it to make it work. I've looked online for tutorials, but nothing this complex. It might not be worth the $50.00 saving to do it myself. Any help would be appreciated -thanks.

 

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will you be working with a all 12v or 110 to 12v?
Will you be using a solenoid with pressurized RO/DI or a holding container with a pump?

Either way I would suggest all 12v.
Here is a wiring example for all 12v
Materials needed:
Float stitches (rated at max volt/amp of pump or solenoid)
12v ac/dc adapter (rated for max volt/amp of pump or solenoid)
pump or solenoid

Basically this is very simple.
with DC current in this situation there is no polarity (positive and negative does not matter)
From the adapter run one lead straight to the pump or solenoid
Run the other lead to a float
from there you have 2 wires from each float.
Run all three in series into the pump/solenoid.
take 2 floats and set them to your desired water level.
Take the 3rd and mount it upside down and inch or two above the water.
The third will be a fail safe in case the first 2 set stuck open by a snail or something. With the third mounted upside down above the water line it will shut things off if the water gets too high.

If you do not know what series is, it's basically running them in line.
Here is a diagram:

Those are LED's but it's the same concept.

If you want to run a 110v pump it's a whole other ball game and MUCH MUCH more complex.
At that point spend the $$ for a ATO system.
 

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Here is a link to a 110v version with relays and 1 float for under $40. you can always cut in more floats. I don't think you can but the materials for less than that.

http://autotopoff.com/products/SS1/
 

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Discussion Starter · #4 ·
I was planning to use a 12VDC 120v-12v relay to drop the voltage. I want to power a submersible pump, but not send 120v through the water level sensors.

I was looking at autotopoff and found the perfect model for $80.00. I can buy the same equipment off ebay for $25.00, and wire it myself. I've never wired a relay switch, and I was confused about wiring 3 sensors in series where they would work properly.

If I wire the sensors in series, then all contacts would need to be "on" in order to power the pump. I can setup the sensors to do that, but when the water begins to fill and passes the bottom sensor it "closes" cut power before water level makes it to the second sensor. I don't understand how to make it fill until it reaches the second sensor than "closes". The third is a fail-safe that "closes" if water reaches it, and the second sensor malfunctions.

I might be so off, and should just buy the $80.00 unit.
 

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Latching relays allow you to latch the relay open or closed until you want to reverse its state. They work best for controlling an RO/DI, as they allow you to set a margin of when you want the filter to operate and not continuously cycle -- which leads to less efficient RO operation and faster DI exhaustion over time.




The simplest system is to wire your three sensors in series, all NC when when the float is down. All three sensors will need to be NC for the system to function. You can set the bottom two switches (or all three if you prefer) at your desired water level, your third at a fail safe level.

12V would run through the float switches to the coil of a NO relay; when all switches reach NC state; the relay closes. When the water level opens even one sensor, continuity is broken and the system stops. The contacts of the relay will switch the hot leg of your 120V to your pump.
 

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The voltage doesnt matter... either way it is a simple circuit to make. I will post up in a couple of days the layout if you want. Send me a PM to remind me. I am out of town right now and do not have the circuit here on my laptop. I would suggest staying away from the eBay float switches as they are prone to failure. Instead look at McMaster-Carr for Madison float switches. I recommend at leat four for failsafe, 2 upper and 2 lower with teh uppers wired in parallel and the lowers wired in series....
 

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Discussion Starter · #8 ·
OK - went with a low tech version, and way easier to install. I bought a 15g trash can, 1300 viaaqua pump, float valve, and digital timer. I plumbed the pump in the trash can to my sump with a float valve. The pump is plugged into a digital timer that goes off 4 times a day for 12min. The tubing is plumbed higher than the water level of the trash can to avoid a siphon. I plumbed a tee from the pump - one going to the sump and the other that vents extra water back into the trash can. If the float is closed then water is routed through the tee (relieving pressure on the float). I installed a Madison float switch as a fail-safe in my sump. If the float valve fails and the water level reaches the top of the sump it kills power to the pump. Hopefully everything works out and no messes to clean up.
 
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