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DIY Dual Float Switch Auto Top Off


yrahim

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Hey everyone so I followed this thread and tried every combination that I can think of, I'm sure I'm missing something very simple but I just can't seem to get my wiring correct. I would like the primary (bigger) float switch to to turn on the pump when the water level in the aquarium drops below a certain level. The secondary (smaller) float switch will be mounted just a bit higher with reverse polarity in case the primary switch gets stuck on, this will turn the pump off as the water level rises past the primary float switch.  I Just don't know how to wire this setting into the relay that I'm using.

 

I have the positive wire from the adapter connected to the primary float switch, which is then connected to the backup float switch, which is connected to the positive port (number 8) on the relay. The negative wire is connected to the negative port (number 7). I then cut and connected the extension cord that the pump will be plugged into to port 1 and 5. 

 

The problem: when the primary switch is activated and the pump is turned on, the secondary switch does nothing. I move it up and down but the pump still stays on. However, if I put the primary float switch up (off position) then the secondary float switch is able to turn the pump on/off. 

 

How do I set it up so if the primary float switch is stuck on, that the secondary float switch will turn the pump off? 

 

Sorry for the messy wiring, I will clean it all up and zip tie everything when I'm finished. 

 

I read through this and tried a few different ways but I couldn't get mine to work: 

 

Thank you in advance! 

Relay Switch Schematic.jpg

ATO Wiring.jpeg

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The behavior you describe sounds correct, depending on mounting.  I don't know what you mean by reverse polarity - mechanical switches are not polarity sensitive- so maybe you mean normally open vs. normally closed?  In this case, you would want a normally closed switch for both - a configuration where both float switches are on when the water level is below both of them, as this will turn on the ATO when the lower switch is not held up by water, and which will break the circuit if the higher switch is floated.

It's probably worth checking that your pump is connected correctly to the relay, as the relay pictured has a pair of normally open contacts (3 and 4) and a pair of normally closed contacts (1 and 2).  The pump should be connected through 3 and 4 (assuming both power lines are switched) so that when the coil is on (when both float switches are not floating), the relay is switched to connect the pump to power.  This pin configuration is presuming you have pump power input on 5 and 6, the relay switches are not polarized so you could have 5 as the output and 3 as the input, for example, and it would run the same.

It's worth mentioning that using the opposite kind of float switches can technically work with a different configuration (parallel instead of series) and the pump connected to 1 and 2 in that case, but then if the relay coil failed, the ATO would be left on, and you'd be continuously powering the coil (more power consumption), so it shouldn't really be considered as a viable option even though the logic of the switches works out correctly.

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17 minutes ago, DaJMasta said:

The behavior you describe sounds correct, depending on mounting.  I don't know what you mean by reverse polarity - mechanical switches are not polarity sensitive- so maybe you mean normally open vs. normally closed?  In this case, you would want a normally closed switch for both - a configuration where both float switches are on when the water level is below both of them, as this will turn on the ATO when the lower switch is not held up by water, and which will break the circuit if the higher switch is floated.

Sorry I meant to delete the reverse polarity bit, I was thinking of something else at the time. The latter configuration is exactly what I want to set up, where both float switches are on when the water level is below them.

17 minutes ago, DaJMasta said:

It's probably worth checking that your pump is connected correctly to the relay, as the relay pictured has a pair of normally open contacts (3 and 4) and a pair of normally closed contacts (1 and 2).  The pump should be connected through 3 and 4 (assuming both power lines are switched) so that when the coil is on (when both float switches are not floating), the relay is switched to connect the pump to power.  This pin configuration is presuming you have pump power input on 5 and 6, the relay switches are not polarized so you could have 5 as the output and 3 as the input, for example, and it would run the same.

When I wire the white wires (extension cord) to ports 3 and 4, then nothing happens when I move either float switch up or down. With this set up the float switches are wired to 7 and 8.

 

I'm using an extension cord, currently wired to the ports 1 and 5 to which the pump will be plugged into. The black plug in the extension cord is my pump, I just didn't want to cut my pump's wire. What do you mean when you say the pump has power input on 5 and 6? 

 

Also I cut the smooth wire in my extension cord and wired that to the relay. 

 

The float switches are wired to the power adapter and which are then wired to ports 7 and 8. Is this set up correct? 

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A four pin relay would probably work, but this one likely will as well.  It's difficult to describe outside of a schematic, but I'll see what I can do with an explanation:
This is for two float switches that are normally on - when the float is not lifted, they conduct, and for the relay pictured.

The pump should go to relay pins 3 and 4, if it's an AC pump then either wire can go to each, if it's a DC pump let's say 3 is power and 4 is return/ground

The input power should go to pins 5 and 6, if AC then it can be either or, if DC 5 is now power and 6 is return/ground

The switches should be connected in series with each other, so from the positive line of their DC power supply to one float switch, from the first float switch to the second, from the second float switch to pin 7 on the relay, and pin 8 of the relay to the DC supply's ground.

That should be all the connections for the relay to be normally open when powered down, then will close when the low level nor high level switch is floating.  If your high level switch sticks, the low level switch will no longer trigger the ATO, but at least it's not failing with the pump on.

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9 hours ago, DaJMasta said:

The input power should go to pins 5 and 6, if AC then it can be either or, if DC 5 is now power and 6 is return/ground
 

Thank you so much for taking the time to simplify your explanation! I really appreciate it. 

 

The only confusion I have is with the above quoted statement. What input power are you referring to? Are you saying I cut the wire for the pump, and wire it to pins 3 and 4. Then take the rest of the wire with the actual plug and wire that into 5 and 6 then plug that into an electrical electrical socket?

9 hours ago, DaJMasta said:

The switches should be connected in series with each other, so from the positive line of their DC power supply to one float switch, from the first float switch to the second, from the second float switch to pin 7 on the relay, and pin 8 of the relay to the DC supply's ground.

 This is exactly how I have the float switches set up. So I'm half way there lol. 

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Yes, if your pump is a normal plug-in type, you'd get a normal AC power cord and connect the hot and neutral connections directly to the relay on 5 and 6.  This configuration may be different than what you originally thought, but if you wire both through the relay, since it's a DPDT relay, you can have both connections to the pump turned off when it's inactive, rather than if you used only one set of relay contacts and left one energized even when the pump is off.  It's a safer approach as you no longer have a live connection in your pump all the time, even though in a properly working pump, that line is completely insulated from the tank and outside.

 

If you get a three prong AC cord (or if your pump uses it), then you'll also have a ground wire (green insulation or just bare copper the whole way, usually) that doesn't need to be connected to the relay, but is good practice to connect it to the box containing all the electronics if it's made of metal (grounding the chassis in the case something fails that would energize it and make it dangerous).  If the pump and the cord to the relay both have three pins, you just tie the ground pins for each together using a wirenut or screw terminals.

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It worked!! Thank you so much for all your help! I had been stuck on this for over a week! 

 

I actually cut my extension cord and wired the socket (where the pump would be plugged in) into 3/4 and the actual plug into 5/6 just like you said. I plugged the pump into the extension cord and it works exactly how I want it to! 

 

Thank you again! You're the best!

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No problem, it can be a bit confusing to get wired right even when the circuit is simple enough, and while something like a schematic makes it easy to understand, that also requires understanding schematics, which is a skill in itself.

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My understanding of the schematic was completely different to how you explained. 

 

Just one more thing, I basically had it all set up then realized the wires on float switches aren't long enough. Can I extend the wire by using any copper and wire connector or do I need a specific wire for these float switches? 

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Shouldn't need a specific kind of wire, but don't use a bare conductor.  I would go with stranded wire, something of comparable thickness of conductor to the original or more - they aren't high current, but sticking with stranded will keep them a little bit more durable vs. flexing.  Actually attaching the wires I'd probably do with soldering, then covering each connection with heatshrink tubing, then bundling the two wires together with that, but if you don't have a soldering iron that gets more complicated.  A more correct way to do it would actually be a crimp of the two wires, but something like a wire nut made for a small enough wire gauge could work as well - the important thing is that there is some strain relief for the connection itself, something that stiffens it somewhat and attaches it to the insulation on both sides.  Basically, the joint is going to be the weakest point even when done well, so you want to build up something that will transfer at least some of any tug on it or bend in it to the stranded wire and insulation surrounding it.  Using solid core wire would technically work, it just wears out from flexing and bending MUCH faster, so it's really only suitable for use in something where there won't be motion between the two endpoints and nothing can get caught on it.

Optionally, you could even put the connection in a little box, but since it should be fairly low current and voltage through it, you likely don't need any elaborate protection for the connections.  If you end up buying something, may I recommend something like low power speaker wire or a twisted pair wire - having two individual strands is more prone to tangling and confusing what end comes from where, so something already bundled together is convenient.

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