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MtnDon
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# Posted: 25 Jun 2015 08:34pm
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Some readers may recall we have a buried water cistern (tank) at our cabin as a part of our water system. No well. For years I used a dipstick to determine the water level. Not a big bother but it became more bothersome when we covered and insulated the access manhole last year. I solved the hassle electronically.
Water conducts electricity. We can use low voltages and very low currents that are completely safe. This is used in RV water tanks. We can buy those systems for $100 and up. Or we can use direct from the Far East parts available on ebay and do it for cheap.
I bought this circuit board....
http://i1373.photobucket.com/albums/ag395/donmiller3/Cabin%20Projects/water_level_PCB _zpsxzh3juhp.jpg
This one came from Thailand. Four connections. One at the cistern bottom, the common wire. Then three more at whatever levels you wish to meter. I chose approx 1/4 full, 1/2 and 3/4 full.
The cistern was already buried so I used a length of CPVC pipe to mount the contacts. I used brass machine screws. The pipe in inserted through a rubber bulkhead fitting in the cistern lid. That provides a good dirt seal.
Here's a couple of shots of the CPVC tube with the contact screws.
more in the next post
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MtnDon
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# Posted: 25 Jun 2015 08:38pm
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Here's a shot of the circuit board. Green LED for the high mark, yellow for middle and red for low. This board runs on 9 volts. I used a 9 volt battery in this one. If I was doing it again I would use a 12 VDC to 9 VDC converter as my plans evolved. We'll see how long the battery lasts. I may retrofit a voltage converter.
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MtnDon
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# Posted: 25 Jun 2015 08:42pm
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That is mounted in a box, also from ebay; Chinese seller.
This is a test of the unit. Press and hold the momentary contact switch to power up and see what LED's light. I have mounted the box inside the cabin near the sink. Originally it was outside on the cistern cover. But then I had another idea and the system evolved.
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MtnDon
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# Posted: 25 Jun 2015 08:52pm
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After that it occurred to me that I could solve another small bother. We have an indoor water tank, like in an RV, for the water we use day to day. The reason is to be able to winterize the cabin but still have water in the in-ground tank that will not freeze during winter absences. We've used manual pumps and an electric sump pump to transfer water from the in-ground cistern into the cabin inside tank. That has worked fine but requires monitoring of the inside tank level by eye and manual operation of the pump. The switch for the submersible was outside. Not a big bother but I'm looking for easier. 
Now the inside tank gets filled automatically. The same submersible cistern pump is used but it is turned off automatically when the full level is reached. The pump also starts up again when the low level is reached.
Here's a shot of the two projects, side by side on the wall near the kitchen sink. The box on the right is the exterior in-ground cistern level meter. The box on the left is the control for the indoor water tank level and automatic pump control.
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MtnDon
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# Posted: 25 Jun 2015 08:54pm
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And a closer up shot of the pump controller.
The rocker switch turns the control on and off. (lettering is superimposed on the photo, not printed on the box)
When starting from an empty inside tank both the red LED's illuminate. The one marked "P" indicates the transfer pump is running. The red LED marked "L" indicates the water level in the inside tank is Low.
As the level rises the red LED "L" goes off and the amber LED marked "M" illuminates. The "P" LED remains on with the still operating pump. The "M" LED has a broad range, from about 2 gallons to 13 gallons.
When the full level is reached the green LED "F" illuminates and the other LED's are all extinguished. That occurs at 14 about gallons.
As we draw off water and the level falls the green LED "F" extinguishes and the amber "M" LED illuminates. The "M" LED remains on until the level reaches Low.
At that point both the red LED's "L" and "P" illuminate again. The pump starts and the tank refills and the whole routine repeats.
The power draw of the control unit is minimal, at the milli-amp level, so I do not worry about leaving the controller on all day. We have been turning it off at night simply to avoid the LED light beaming across the room. When we leave all power is turned off.
Box,control board, 12 VDC to 5 VDC power supply and switch are all direct China ebay imports. Total cost was less than $15. There was a glitch as sometimes happens on these direct China imports. One of the soldered circuit board connections has a component wire bent. When it was soldered a solder bridge was formed. That prevented the relay from operating correctly. Fortunately it did not cause any component damage. However it was inconvenient. The vendor was apologetic and refunded $2 of the $4.89 control board price though. So the cost is less than $13. Not bad for a now automated system.
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MtnDon
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# Posted: 25 Jun 2015 08:55pm
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I forgot to mention one important detail. [headslap]
The unit works by using / measuring the conductivity of water. Water has to contact these points and the very low voltage, low amperage current path is completed through the water. There are special contacts made for RV tanks. I used a home made solution. Well nuts are rubber "sleeves" with a brass threaded fitting molded in one end.
Drill a hole, insert the well nut, tighten the screw with the wire connected under the bolt/screw head. They are squished, shortened and the rubber seals the hole. They do have a problem when using in a tank full of a fluid like water. The threads are not tight enough fitting to seal the water perfectly. A little bit of silicone sealant solves that. They are meant for blind fitting where you can not reach behind.
If I had easy access to the top of the tank I might have used a solution like I did in the previously illustrated exterior in-ground cistern. That would have meant pulling the tank which would have included disconnecting lots of plumbing. I tried the well nuts in an old pail and was satisfied.
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Gary O
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# Posted: 25 Jun 2015 11:22pm - Edited by: Gary O
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MtnDon, five years ago yer wizardry ceased to amaze me.
However, I still find myself leaving my mouth open when I read of your exploits.
If only you were present in that think tank I was a member of ten years ago.
One of us would be not near as poor...but then I hear yer pretty deadly with the black powder artillery...
So let me get this straight;
The doohickey detects water level thru electricity, right?
Damn, I bet it prolly is ardy out there, but worth a search.
I was involved in wunna the first fingerprint lock releases for personal weapons.
I didn't do any of the tech stuff, but came up with some pretty nifty slogans;
GRYPP
Heh, can't recall what the acronym contained (Gun Retrieval Y?? Personal Protection), but my verbiage;
Be safe
Be ready
Get a GRYPP
got the big money folks worked up into a bit of a froth.
so-o-o-o, if you ever need a slogan...
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FishHog
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# Posted: 26 Jun 2015 07:23am
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Great idea don and a great tutorial
Thanks
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Don_P
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# Posted: 26 Jun 2015 07:30am
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Quoting: MtnDon I tried the well nuts in an old pail and was satisfied
I dunno, seems like a good slogan to me already
Neat setup. The old motorhome had a similar setup but being from '73 they were analog meters on a panel over the fridge with a manual pushbutton contact switch to check. That worked fine until the dozer shoving in to a jobsite helped clean up the underbelly of the rig.
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