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DIY Auto-Top-Off (ATO) System
- Thread starter JWeb
- Start date
Nice work guys,
Just a word on switch cycling / reliability. I'm using the same switch (vertical) to switch on a DIY I did years ago. Mine switches a relay that in turn switches a peralistaltic pump. The "throw" on these is close to an inch so there is no hair trigger effect.
BTW
My single float switch version is running now for over 3.5 years without drama.
Just a word on switch cycling / reliability. I'm using the same switch (vertical) to switch on a DIY I did years ago. Mine switches a relay that in turn switches a peralistaltic pump. The "throw" on these is close to an inch so there is no hair trigger effect.
BTW
My single float switch version is running now for over 3.5 years without drama.
RobboT
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On this subject, I am not an electronics expert so maybe someone can help with this. A latching relay is what is needed to have the pump turn of on the bottom float and off at the top float. When the switch closes on one side of the latching relay the power goes on, when the switch closes on the other side of the relay the power goes off. Everywhere I look these things are $30. Can anyone explain to me what the difference between a plain old relay and a latching relay is?
NateHanson
Non-member
I believe the purpose of a plain old relay in these setups is just to take the 12V signal from a sensor (the switch in your sump) and close the 120V circuit for your powerhead. It avoids having 120V in the sump.
A latching relay does just as you say, and adds a separate on and off signal circuit for the relay.
All that said, I'm a furnituremaker, so you'd be wise to take it all with a grain of salt.
A latching relay does just as you say, and adds a separate on and off signal circuit for the relay.
All that said, I'm a furnituremaker, so you'd be wise to take it all with a grain of salt.
NateHanson
Non-member
Sounds like the same thing as Nuno said Casey.
NateHanson
Non-member
yep, sorry.
nunofs
Non-member
Because the switches are not wired exactly as you described above: the bottom switch turns on when the water level drops, triggering and latching the relay... it turns off when the water level goes above it, doesn't matter to the relay, as it's already latched on the active state; then when the water level reaches the top switch, it turns on and trigers the relay, which goes to inactive state. As evaporation makes the water level drop, the top switch eventually goes back to off (no impact on the relay), and the bottom one eventually turns on again, repeating the cycle.
Anyway, long explanation, hope it makes sense, but the important thing is that the two switches are wired differently, the bottom one is inverted.
Nuno
Anyway, long explanation, hope it makes sense, but the important thing is that the two switches are wired differently, the bottom one is inverted.
Nuno
nunofs
Non-member
Btw, this doesn't apply in case you're using the second switch as a redundant backup... in that case they're both wired the same way... and you don't need a latching relay in that case because the switches will be on for as long as the pump needs to run so the relay doesn't need to keep any state.
Nuno
Nuno
RobboT
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Sorry nuno I should have said "in the case of the standard relay". I understand the latching relay concept. Of course then I read back and saw the post by Nate that I missed about using a 12V source to control a 120V circuit and now it makes sense.
So . . . anyone know where to get latching relays inexpensively?
I should say latching relays that are entirely AC based.
So . . . anyone know where to get latching relays inexpensively?
I should say latching relays that are entirely AC based.
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dedfish
That's Mr.Murphy to you!
Here's a link to my auto-topoff. I haven't really used it full time yet, but all the test's I've done have worked out great. I just finished re-engineering the float switch bracket so it's a little different than the pics. The float switches have to be in the tank in this setup, or it would have been much easier. I use a relay so I don't have 120v flowing through float switches sitting in saltwater. There is a diagram at the bottom.
http://216.235.242.50/forums/showthread.php?t=2318&highlight=auto+topoff
http://216.235.242.50/forums/showthread.php?t=2318&highlight=auto+topoff
RobboT
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OK Marvin, you got it. Looks like Im going to be building a few of these. 
As far as the 120V in the water issue . . . I tested my tank last night and have no stray voltage in the sump so Im not so concerned about it. Besides I've got a powerhead hanging directly in the main tank, and a 500W heater, a Mag9.5 and 2 Sedra pumps on my skimmer in the sump.
As far as the 120V in the water issue . . . I tested my tank last night and have no stray voltage in the sump so Im not so concerned about it. Besides I've got a powerhead hanging directly in the main tank, and a 500W heater, a Mag9.5 and 2 Sedra pumps on my skimmer in the sump.
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dedfish
That's Mr.Murphy to you!
Rob, no stray voltage today...but what about tomorrow or the day after that? What about the day you have to move something or disturb the wires, or god forbid spill some water or have a leak. All these items you buy have been UL certified and approved. A topoff system you build which uses float switches NOT designed for that much voltage is a hazard. If you want to run 120v through a very fine guage wire (all the float switches I've seen have very thin wire) and then stick that in a tank off saltwater...very well then. Just check the specs of the switch and make sure it can handle it, my bet is the switch can't.
I just think that $20 in parts is worth my life and yours.
I just think that $20 in parts is worth my life and yours.
