Magnetic interference and ATO switches

[cdness]

So I always say that I am always learning something in this hobby. Last night I had a local club member over to grab a couple frags and he noticed the buzzing or fluttering sound coming from my ATO controller relay. I told him the float switches are probably going bad and I need to replace them.

He peeked at the sump and noticed my float switches were immediately above one of my return pumps about 3 inches away. He then said to take the union off and rotate my pump 180 degrees to keep the float away from the motor housing and it should stop. After he left I instead moved the switches to a different place on the return section of the sump as it was easier than moving the pump. Miraculously there is no more flutter or buzzing sound coming from the system and it works as designed again!

I never thought magnetic driven motors would interfere with the switches. This just proves the point that no matter how long you are in the hobby, you are always learning new things.

 

[AZDesertRat]

Was it magnetic or fluctuations from water movement near the pump wiggling the switch? Does your ATO have a latching relay to help eliminate nuisance chattering like that? Also is the ATO 12 or 24v DC rather than 120v AC, this really helps switch life since AC creates quite an arc inside the switch when it makes and breaks contact.

 

[cdness]

DIY ATO circuit using a 12V relay as I do not like 120V running that close to water on small wires...

It is not a latching system as I control the amount of time it is on via timer. I don't want it to drop to a certain level in order to start the ATO as it is just another failure point. The level is controlled by a single float switch with a backup to kill the system about an inch higher in case the first float ever fails. I have only replaced the switches once in the life of the hobby for me which is well over 6 years.

There is barely any water movement in the return section. I had an issue with sloshing before, but with the new sump design, there is hardly any movement of the water on the top of the return section. The switch doesn't wiggle at all.

 

[AZDesertRat]

Interesting. I guess motors have a pretty powerful magnetic field, enough to interefere with switch contacts. I have heard similar tales about powerhead magnet mounts and probe interference causing controllers to do wacky things.


I use dual float switches set 12" apart and a solenoid in my ATO storage container but it is very still compared to a sump. in my sump I use a digital air sensor, UPLC-II similar to the Tunze sensor so magnetic fields and turbulence don't affect it.