Diy Auto Top-off

[dwall174]

I have been looking into trying to build a Diy auto top-off system! I will be using a 20gal tank for RO/DI water storage! I'm thinking about using this type of Float Switch for high & low sump levels? I also want some type of "small" switch for the main tank to prevent a flood if the overflow got blocked some how?
I came across this schematic for a DIY top off! Does this look like a good plan? or is there anything else I should add? Thanks!!

[Geoff]

sorry, but i am a mechanical kind of guy. i just used a Kent float valve on my system. i have it plumbed into the house plumbing. i have never had a problem with it. granted it has only been up for 10months. i also plan on using this system for Nikki's tank when it gets set up.

i was hoping someone with more knowedge about circuits would pipe up. i can tell you what all the symbols mean. and that is it.

G~

[dwall174]

I know what you mean! I’m also the mechanical type I do know the basics about electronics but I was just wondering if it look like a good plan or is there something else that would be helpful to add?
I could always take the easy out and get one of THESE for the sump & one of THESE for the main tank?

It’s just that “Need to Build Things” kicking in

[Schwaggs]

It does look like a good plan if you can find reliable float sensors. I like the main pump cutoff when overfull. I would be worried that one of the float sensors would fail and put water where it doesn't belong. I use a slow, constant gravity fed drip.

[dwall174]

The schematic above looks like it would use SPST relays with a 12 volt AC coil? Would it be easier to just use a 110 volt SPDT Relay? What would be the advantage of using a relay with a 12 volt coil over one with a 110 volts AC coil?

[wanareef]

12vd would prolong the life of the float switch ifonewas being used. 110 will in some time arc the contacts closed in a float swith and you would get a flood - as what happened to my tank

hth

[dwall174]

Ok after reading some more about the advantages of using low voltage for the float switches! I have decided to go with relay's with 12-volt DC coil's! As I stated, I do know the basics about electronics! However, I’m not sure about matching the power requirements of the three relay’s coil’s to a 12-volt transformer?
Any ideas?

Here's the Float Switch I plan to use!

[PJenkins]

If you use the circuit shown you might want to use diodes across the relay coils and capacitors (.1 uf) across the relay contacts. The diodes will protect the coils from current surge when the relay is de-energized. Place them so the cathode (the side with the stripe) is attached to the + positive side of the rectifier. The caps will protect the contacts from arcing that occurs when switching line AC.

[dwall174]

Originally posted by PJenkins
If you use the circuit shown you might want to use diodes across the relay coils and capacitors (.1 uf) across the relay contacts.

I dont know much about Diodes & Capacitors? Could you explain a little better on how to install them?
Also what else do I need to know to order the Capacitors & diodes (size, style, value?) Thanks

[PJenkins]

Sorry! I should have given more info and checked my typing closer. The capacitor value should be .01 uf and the type can be either ceramic disc or mylar with at least a 300 volt rating. These caps are non polar so you don't have to worry about which wire goes where, just put across the contacts of the relay. The diode can be just about any small rectifier type or signal diode a 1n4001 is a common one . These parts can be bought at your local R. Shack i'm sure.

[dwall174]

Thanks for the information!

“you might want to use diodes across the relay coils”

So if my understanding of electronics is correct a diode is like a check valve! And will only let the current travel one way? By across you mean from + to – correct? And as for the capacitor it would just go from one contact to the other?

[PJenkins]

in this case the diode is there to protect the relay coil from backlash current that CAN occur when the coil is suddenly energized/de-energized. It becomes more important when using relays that utilize small gauge wire in the coils. The backlash current spike can be enough to open the coil like a fuse does when it reaches its max current. The beefier the wire used in the relay coil the less of a concern it becomes, but its cheap insurance and may keep you from having to replace the relay prematurely. You wire it in a reverse bias condition, that is you connect the cathode (-) side to the positive (+) side of your dc relay and the anode (+) side of the diode to negative (-) of the relay coil. Does that make sense? basically you will shunt or short the REVERSE current that spikes briefly when the relay fires , through the diode. By the way you wouldn't use a diode at all if the relay coil was an AC alternating current type.

The capacitors will protect the relay contacts from arcing when switching AC line current, which is what you are going to be doing. You would connect them at the same place you connect your motor wires.

[dwall174]

That's scary I think I actually understand it I looked around & all I was able to find localy was 12 volt DC Relays! thats why I stated that I planed to go with DC instead of 12 volts AC Thanks again for the help

[mnreefgeek]

Doug - one note on that switch. I really like the way it works, but watch the mount that comes with it. I don't know if you caught my thread about a week ago, but that's the same one that failed on my tank. David was quick to replace the mount, sent me 2 for free, so kudos to him. Like I said, not knocking the product, just a heads up.

[dwall174]

Thanks for the heads up! I was planing to mount it in a holder like THIS ONE The granger float switch that's listed there is like $14.00?