Float switch troubles

[The R/C Man]

Well I have installed a seleniod for my RO/DI to top of my tank when the float switch drops a bit. Unfortunately the switch is to sensitive and causes the relay to chatter. I have installed the switch inside a piece of PVC to keep down the water movement to no evail. These switches worked great when operating a pump for topping off. Anyone have any ideas on how to fix it?

Thanks!

[The R/C Man]

Maybe I should have put this link up before. It is a small switch with very little travel.... http://www.floatswitches.net/floatswitch.html

[barebottoms]

Read Weatherson's anti cycling thread and adapt that for your float instead.

Or run another float to serve as Min and Max points.

So boolean would say, if min is on and max is on then power solenoid.
If Max is On but Min is off then don't power solenoid.

You can complete the rest of the truth table and make adjustments for if your Float is NO or NC

[xrunner1234]

I use the same float and I have no problems. Can you post a schematic?

[nyoneway]

Why dont you run the power solenoid on a timer.

[xrunner1234]

Oh, and how long does it chatter for?

[Thirdson]

Originally posted by nyoneway
Why dont you run the power solenoid on a timer.
This is exactly what I did. I am using the same switch as you and have a timer set to turn on twice a day for 15 minutes each. So far it's worked great.
I originally wanted to setup two like barebottoms suggested but accidently burned out my second switch.

[beerguy]

One way I get around chatter is by mounting the float in the sump and adding the top-off to the tank. Because there is some delay introduced that way, each operation slightly over-fills the tank.

[The R/C Man]

Thanks Guys! Some great ideas... I'll draw up a quick diagram and post it.... Basically I cut one side of an exstension cord and wired in two float switches. One sits at the water level and acts as the main switch for the solenoid. The other is up higher in the sump and is a back up in case the other sticks.....

[ReefMeister2]

As an extra safety measure, I routed the "output" of my ReefRelief solenoid system through a standard Kent float valve. Even if both vertical float switches for the solenoid were to stick/fail, the Kent valve would prevent any water dumping into the sump accidentily...nearly foolproof! I hooked my unit directly to my RO/DI unit...no pumps/no reservoir/no hassles. It has performed flawlessly.

[tricky]

R/C,
You are on the right track with the PVC pipe. The chatter you are getting is likely due to the "wave" action of the water rapidly opening and closing as the water level is nearly satisfied. It is not a good thing because it can cause arcing on the relay terminals (or worse, your float switch), and eventually fail. This is assuming you are using a low voltage control and a relay instead of wiring 120V to your sump.
What you need is "hysteresis" ( 'retardation of the effect when the forces acting upon a body are changed' .....blah bla). Let's just call it a dampening effect.

A couple of things you can do:
I put my float switch in a small cylinder, like a clear 35mm film canister with a couple of vent holes near the top, much like your PVC pipe. This will provide both snail, critter, wire and other object protection against sticking, and provide a dampening effect of surface water changes. The longer the cylinder, the more dampening effect.

Electrically, you can build a small amound to delay into the relay closure. This can easily be done by controlling the relay with a DC voltage, then add a large capacitor across the relay coil. When the switch disconnects power to the relay, the capacitor stores enough power to hold the relay closed for a small amount of time. As the stored power in the capacitor is used up, the relay will drop, stopping your makeup water. A 2-3 second delay works great. As you can see, the makeup water will not shut off untill the float switch quits bouncing, giving you a smooth shutoff.
One more thing to include with DC control to a float switch relay is a "transient voltage suppressor". Without a lot of detail, it is a diode, also placed across the relay coil but in reverse polarity. It does nothing when the relay is energized, but when the float switch opens, it will short out the energy stored in the relay as the magnetic field collapses. Without it, the "transient voltage" from the relay coil can cause a very small amount of arcing in the float switch contacts and eventually cause it to fail.

[The R/C Man]

Thanks Tricky!

You have some great ideas. I ended up adding a fitting to the end of the tube (slip/thread) and screwed a strainer into that. So far it is working great. I really like your idea of a delay but I need to see a scematic to understand it. I do some eletrical troubleshooting at work but mostly just to find a faulty circuit card or component and replace it. Not really in-deapth stuff. Thanks again!

[tricky]

RC,
Here is a simple schematic, hope it helps:cool:
http://home.cfl.rr.com/teamloewen/images/Floatswitchschematic.gif

[ReefMeister2]

It seems like beerguy's suggestion is a brilliantly simple, yet effecitve way of inducing the same "delay" that tricky is suggesting...but without the complex schematics.
For some reason I never get the chattering effect with my float switches. I don't know if ReefRelief already thought of this and installed the electrical-delay components into their solenoid system (tricky's method), or if my adding the Kent float valve to the output induced a physical-delay effect (beerguy's method)

One temporary problem I did have was this weird wave-like oscillation going on inside my center (return pump) compartment of the sump. It literally looked like a miniature wave pool inside my sump! I suspect this phenomenon occured because of an unequal distribution/flow of water that was entering the center compartment from either side compartments: 90% flow came from filtersock/skimmer compartment (left side of sump), and only 10% flow came from the refugium compartment (right side of sump). These "rogue waves" caused the floatswitches to cycle on-and-off, but I solved that probelm by simply adding a short 2" tall piece of acrylic near the center water line; a sort of "partial baffle" if you will... it stopped the oscillation (wave action) immediately.

To sum it all up:
I would try to think of simple "physical solutions" before resorting to electrical solutions if at all possible. For instance, I didn't want to have anything to do with having to build a separate reservoir tank, just to hold fresh water, and then have to depend on ANOTHER pump to transfer that water into the sump...especially when the existing water sources were ALREADY pressurized (including the RO/DI). The whole idea just seemed completely silly to me. So I attacked the safety issue (fresh water/accidental dumping) head-on with a "direct solution" (third redundant float switch) instead of trying to counteract the threat with a more complex "indirect solution" (seperate reservoir/pump). In fact, a more complex "solution" will often introduce more opportunities of component failure than the original problem had to begin with.
Soooooo....I guess there is substantial credibility to abide by the K.I.S.S. method afterall! :)


(confession)
ummmm....obviously the K.I.S.S. method does not apply to my writing style...sorry if my descriptions are confusing. :p

[bounce]

I replaced the standard relay with a single shot time delay relay. The time delay is adjustable from 2 sec to 2 minutes. This solves 2 issues: No more chatter and reduces the number of times my pump cycles on and off. Time delay relays cost more but I havent had to replace my pump this year.

[The R/C Man]

Tricky,
Thanks for the scematic....

bounce,
Where did you get the relay and do you have a part #?

[jfinch]

Barebottoms hit the nail on the head. Buy another $6 float switch (or just use the one your using for overflow prevention).

Wire it up like this:

http://www.utahreefs.com/forum/uploads/jfinch/2004-09-18_102400_floatwireing.jpg


And this is what my two floats look like:

http://www.xmission.com/~jfinch/floats.jpg http://www.xmission.com/~jfinch/floatsinstalled.jpg

The water level in the sump is maintained between the two floats so your solenoid only has to come on a few times per day.

[The R/C Man]

Cool!

What type of relay and where do I get one?

[jfinch]

I thought you said in your first post that you had a relay?

Relay's really extend the life of the reed switch in your float. I bought the relay and socket at a local electrical supply store. The relay was about $6 and the socket another $4. Almost any DPDT relay will work. This is what mine looked like installed:

http://www.xmission.com/~jfinch/relayinstalled.jpg

[bounce]

McMaster-Carr
732-329-3200
www.mcmaster.com
part#7096K22 Single Shot relay
Part#7122K19 Socket for 8 pin relays
You must specify the input voltage I chose 12VDC because I had a 12 volt DC power transformer.
The socket makes attaching the wires easy and holds the relay. I mounted mine on the side of my sump. If this is how you decide to go I can send you the wire diagram.
The only down side to this setup is that if your float switch stays on (make up water runs dry) the relay will not fire again until the float switch completes its cycle.