The Ultimate Float Switch

I hope this topic isn't too controversial .

Just thought I'd share my latest trick.  I just got an RO/DI unit so I needed a way to automate the tank topoff.  My old single float switched to a refilling powerhead just wouldn't do here.  Here are the parts I used.

This a picture of the solenoid valve.  It's powered by 120v AC.

Here's the relay and socket:

Here's the two floatswitches in a diy adjustable holder:

The concept behind it isn't my own.  It's very common in industry when controlling levels to set up two switches this way.  It's called a "pump up" scheme.  What it is, is two floatswitches wired through a DPDT relay with one of the contacts operating the solenoid.  When the water level drops below the lower float, the solenoid is tripped and RO/DI water flows into the sump.  When the water level fills high enough to trip the upper float the solenoid shuts off and is reset.  This method of control is preferable over a single float because with a single float the solenoid valve would be constantly coming on and off.  With this method the solenoid only comes on a couple times per day.  Also it's better on the RO to run continously rather then in short bursts.

The solenoid is plastic bodied from www.mcmaster.com part # 7877K23:  $17.18

The relay and socket I got from Standard Supply in SLC:  $10

The floatswitches from www.floatswitches.net  : $15

Acrylic I had laying around, the RO line connectors from Home Depot.  All in all, I think it ended up costing about $50.  It works like a champ!  Here's a few pictures of it installed.

The relay:

The solenoid valve installed:

The float switches in the sump:

Jon, of course, fantastic job! Your DIY skills are unmatched. Just a thought on the floats and overcycling the solenoid. Somewhere, and I cannot remember exactly where but I will look, they make a float switch with adjustable travel so that you wouldn't need an extent type system with reset. Basically it allows an increased or decreased travel in the float which is on a switch. Not that your method is bad because it's great, just advising of an option that I use at work.

Again, great job!

Jon, I will see if we have an extra mechanism laying around as well. We'll talk about it next time we see each other.

I think that I can find it cheaper, but just to give you an idea... http://www.grainger.com/Grainger/productdetail.jsp?xi=xi& ;ItemId=1613544591&ccitem=

Sean,

Crazy I was just thinking about this as well.

Adam

Jon,

You have Chitons?  Where did you get them?

Jake,

Not sure where Jon got his.  Don't know of any local store currently selling any.  But they retail online for $2 so they can't be that hard to find.... well maybe they can be.

Adam

Here is a picture of a chiton.  Although not all are as colorful as this one.