Plea for an ATO design please

Home Forums DIY Tank Equipment Plea for an ATO design please

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    I’m after an instructional to make a fail safe ato to go in a back sump of a nano I’m setting up please.

    I use an optical Aquasmart in my main tank which I like but money constraints mean I would rather DIY one for this new setup.

    It has to be neat and small as the back sump will be lit as a refugium and on view.

    I have no experience in any of this so please explain like I’m a dimwit. All I guess is, I need a float switch or optical sensor mounted somehow – I guess both would be more failsafe ( I really struggled to find epoxy coated neodymium magnets last time I tried, at a reasonable price) and small pump. I then somehow by sone crazy magic wire them together and bobs your uncle an ato that will never fail and lead to divorce with ‘flooded the effin house’ cited as a reason.

    If you could link or tell me where to get the bits online even better!

    Many thanks all


    Okay. For super simple. I’d do two float switches. A relay. 12v and power plug.
    You could probably do without the relay if the pump is low powered.

    You get little coin protectors from fleabay that will fit a small neo magnet in.


    How would I wire and set all this up please, sorry. Think I could blag it but I’d rather know properly.


    Where abouts are you located? I’m in the process of setting up a new larger tank and have plenty of space and dont have any of the fish you have mentioned sorry correction I have one clown but it can be kept in my small tank so not a problem.

    I know this is not a sales thread just wanted to show that if it was something you wanted or needed to do I’m able to help depending on location


    I did mine with a microcontroller. But the switches can be used in circuit for low amp pumps.
    Not sure I can post fleabay links? But the one I use is a 3 or 5 w pump for pc water cooling.
    When you’re messing with the float switches if you take the c clip off and spin the float around it will work backwards.

    So one way will be float up circuit disconnected and the other way will be float up circuit connected. If that makes sense.

    So wire them all in one big loop. Then if the float sinks the circuit will be complete. But if that gers stuck the second one will float and break the circuit.

    If you want a high power pump. You will need a relay to handle the juice.


    The DIY section has an ATO using three floats and a solenoid which i have built for about £30. You could simplify to a one float design, but i would consider buying a reefloat ato unit as they are well prices compared to DIY really although the arduino approach above looks very good and small.

    Do you have the links to build that periint ?


    I’ve just gone back from arduino version but that worked more smother than my anolog one I’ve just made. But for quickness I went this way.

    Three floats as pic above.
    A 12v 30amp Bosch 4pin relay ( Halfords 6 quid but much cheaper on eBay. )
    12v caravan pump.
    You’ll need a 12v supply about 2 amp. Penny’s on flea bay.

    To wire up you simply have power supply 12v + to one side of relay switch and one of the power terminals.

    The power supply 12v- wire to the pump directly.

    a wire from the supply 12v- threw all three float switches to the other side of the relay switch.

    A wire from the last power pin of the relay to the pump +

    The floats are one for overflow. One for topup tank empty and one for water level.

    Fail safe way of doing it but you could go right down to 1 float if you want.

    About 20 quid


    As above I did an analogue one.
    Was going to use arduino bit thought for simple ato it would be a waste.

    I got 2 float switches a 5v usb pump (needs 2 amp supply for the head I needed)
    Wired as above but with only 2 switches.
    Use more than one as a failsafe.

    A green led and resistor

    Got a black gloss project box from maplins and stuffed it all in.
    Green led lights up when pump running. Double sided Velcro it to cabinet.

    For the floats I used a piece of 6mm acrylic and bent the top so it hooked over the top of my sump.

    I mounted the float switches inside a small baby container upside down with lid off. (This helps if any movement in water to stop it going off false.

    Works a treat and the gloss project box looks great as well.

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