# DIY ATO (Auto Top off) for $25



## jmatkowsky (Nov 22, 2012)

I had some time at lunch so I figured I'd sketch out how to make a DIY ATO for under $25.

These are the parts needed and can all be bought from Aliexpress.com which includes free shipping and no duties or taxes. Will take 2 - 3 weeks to get all the parts. See diagram for details. I'm terrible at drawing so my apologies for the ghetto hieroglyphics.

The basic idea is that a relay acts as a switch and controls the live connection of a power cord (120v). When 12v power is applied to the switch, the switch is engaged (open) and a live connection is made, passing power to the socket (120v). When the 12v power is cut off, the relay closes the switch and power is cut to the socket. A 12v adapter is spliced so the live (red) cable is connected to a series of floats. Depending on if the float is up or down, 12v power will be passed along (or not) to the relay. This is how 120v power turns on to control the pump. If you put a series of floats, 1,2 or 3, you can have them each do something to control the power. If using 3, the first in the series should be for cutting power when the water in the top off tank drops below a certain level so your pump doesn't run dry. The 2nd float will act as a backup and will cut the power if the the water in the sump goes above a certain level- to prevent the pump from running if the 3rd float switch is stuck for some reason. Then the 3rd float is to pass power when the water in the sump drops below a certain level and once the water water pushes the float back up, it will cut power. Float 2 should be an inch or 2 above float 3. Float 1 should have it's float reversed. You can remove the white float by taking off the small half circle disc at the end and reverse the float. This way, it will close the switch/cut power when the float is down (and your top off tank drops below a certain level).

1 x 12V Relay switch with base ($6.50)

http://www.aliexpress.com/item/12V-...N-5A-With-PYF08A-Socket-Base/32230878151.html

1 x 12V power adapter ($4)
http://www.aliexpress.com/item/New-...or-DC-12V-2A-24W-Power-Supply/2051934100.html

2 - 3x float switches ($ 5.50)
http://www.aliexpress.com/item/New-...zontal-Float-Switch-3-Pcs-Lot/1527985138.html

1 x Junction Box ($5.50)
http://www.aliexpress.com/item/FREE...lack-10-3x6-4x4cm-Waterproof/32234734917.html

1 x power cord ($2) From dollar store

1 x power switch (not necessary) ($1)
http://www.aliexpress.com/item/1PCS...SPST-Switch-Round-Rocker-For/32246770357.html

2 x led indicator lights- one to show when pump is running (led will be on) and one to signal when Topoff tank is low (this led with turn off) (not necessary) ($1)
http://www.aliexpress.com/item/AD16...r-Pilot-Lamp-DC-12V-20mA-New/32260279649.html

1 pack of suction cups for floats ($1.75)
http://www.aliexpress.com/item/Whol...ne-Tube-Holders-Clips-Clamps/32255847498.html

2 - 3 meters of wire ($1.50)
http://www.aliexpress.com/item/Dual...red-and-black-cable-and-wire/32294267000.html

You can use any pump- small powerhead(if not too much lift/head pressure), or the one i have (Tom Aqualifter). ($18 on amazon) 
http://www.amazon.ca/Aquarium-Aqua-...id=1426892414&sr=8-1&keywords=tom+aqua+lifter

I had a JBJ Auto top off, but it died as i had it hidden under my cabinet where my sump is. The electronics don't like the humidity because it actually has a pcb board that goes finicky with humidity. Plus, it would shut off my Tom Aqualifter pump after 1-2 minutes even before it got a chance to top off the water and reset the float. When the float isn't reset, it doesn work. And, you can only have 2 float switches.

This DIY has a Electromagnetic switch so no electronics to get messed up by humidity and its more durable IMO.

Anywhoo, it was a cool project and i'm happy with the results. It works alot better than the store bought one.

Cheers!


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## sig (Dec 13, 2010)

Thank you for posting. Much appreciated

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## jmatkowsky (Nov 22, 2012)

np... are the links working? I just updated them because I think they got messed up.


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## altcharacter (Jan 10, 2011)

The only thing you forgot was the actual pump.
Nice work though. I'm going to try one when I get some time


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## jmatkowsky (Nov 22, 2012)

You can use any pump- small powerhead(if not too much lift/head pressure), or the one i have (Tom Aqualifter). ($18 on amazon)

http://www.amazon.ca/Aquarium-Aqua-...id=1426892414&sr=8-1&keywords=tom+aqua+lifter


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## 4pokguy (Apr 27, 2011)

Great idea of putting in a power switch. I have the DIY ATO from BRS, and I find it annoying to have to unplug the pump when my hands are wet. I'm gonna add in a power switch to make things easier.
I found this link for the same switch, but for less. And it also has a faster shipping/delivery time:
http://www.aliexpress.com/item/1PCS...e-Car-Boat-ON-OFF-SPST-Switch/1721501857.html


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## kookie_guy (Oct 15, 2014)

One thing I would keep in the back of your mind, is that those are cheap relays, and are very prone to having the contacts weld when switching 110 AC. I realize your draw is minimal (depending on the pump you use) but it will still eventually fail. I design, build, and program control systems, and see it happen all the time, even with DC applications.

What you need are force guided relays that are used for safety circuits. They have a mechanical interlock that forces the contact to break apart when the coil is de-energized, so welding contacts is not an issue.


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## kookie_guy (Oct 15, 2014)

Also, your switch should be closer to the wall wart, before you break off into your float switches. I'm assuming you are using an illuminated power switch? Otherwise bringing the black wire to the switch is not required.

The LED that you have right by the relay. What is the purpose of that LED? To show when the pump is active? Or to show when you have power being supplied to the float circuit? If to show when pump is on, then it's correct, otherwise it has to be before the floats, right after the power switch.

And terminology wise, when dealing with DC, don't use the term neutral, as that's used with AC circuits. Say common, return, or 0vdc.


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