nigelmercier
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DIY Water Tank Gauge
- Thread starter nigelmercier
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pvb
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That's intriguing, is the readout in litres?
nigelmercier
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The two tank senders have a number of switches (16 and 20), so the output falls into one of a number of "slots". The large numbers show the midrange of the slot, in litres; calibrated by noting the readings on the D/A converter while filling the tanks.
The bargraph is this number as a percentage of the maximum value for the tank. The filled > character points to the aft tank, as this is the button that was pressed.
The smaller 999 on the display is just debug info from the sensor reading the ambient light, used to set the contrast of the OLED. Note that the circular PCB is 50mm diameter, so may appear rather larger than actual size.
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Norman_E
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Nice project! I just went a much simpler route with my boat, which has tanks about 700mm deep. I used Kemo water level indicators from Maplins, and home made senders. The indicators have 10 LED lights and each one that is on represents 10% of the tank's capacity.
Hydrozoan
Well-Known Member
Yes, I did that and fabricated a sender unit from ribbon cable with 'nicks' in the insulation at appropriate depths. Simple, inexpensive and no moving parts. Nothing like as neat as Nigel's gauge though, so mounted behind a locker door!
superheat6k
Well-Known Member
Can you kindly elaborate on the home made senders please.
Ok I have just found it on the Maplins website, so all is explained.
How reliable does it seem ?
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vas
Well-Known Member
+1 as I have a sight gauge on my water tanks (that are about a metre high!) and a resistive system on a wire that I could slide in the transparent tube would be ideal for me (if I got the concept right...)
cheers
V.
superheat6k
Well-Known Member
Vas
This works by multiple probes
Link to manual here. Maplins are a shop based electrical / electronic supplier in the UK. If you want one let me know and I will post it to you.
https://maplindownloads.s3-eu-west-1.amazonaws.com/N16DD-Manual-4877.pdf
Hydrozoan
Well-Known Member
As Norman_E has yet to respond, this is how I did it. As you may know, the Kemo units# have separate circuits for each of the LED lights so that - in the example application they gave which I recall - there were 10 separate wires terminating at different levels in a garden water butt, attached to a vertical board. Such an arrangement struck me as cumbersome for a boat water tank, so I took a length of computer ribbon cable and carefully cut away the insulation on the different strands at depths appropriate for my tank (a bit fiddly, but perfectly do-able). I then cable tied the ribbon cable to a stiff but flexible stalk (I happened to have plastic covered curtain wire) which was epoxied into a plastic inspection cover in the tank.
It has worked well for over 5 years - after the tank has been drained over winter, the ribbon cable contact points get a bit 'iffy', but the first fill or two with chlorine-tabletted water restores the contacts. Sometimes the lower level lights are dim - but it's only the top one that matters anyway.
I hope that helps, but Norman_E may have an even neater way ...
# See link given by superheat6k for the Kemo units - they are of German make, and mine is an older - but essentially similar - version. In the UK they cost ca. £30, and what I like is the absence of any moving parts.
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superheat6k
Well-Known Member
Thanks. Now I have found the manual I was thinking of making the under inside a piece of plastic water pipe, but first need to see how I can mount the sender assembly to the tank.
This is a rectangular tank approx 500 lts. I was surprised to find the maker didn't bother with a level gauge.
I also have a second wing tank in parallel with it on a common low level balance pipe, but as the levels will settle to the same height I only need one sender, although the list the boat takes on when filled is remarkable.
vas
Well-Known Member
Thanks Trevor and Hydrozoan for the explanation and pointers.
Actually since I just managed to sort my arduino analogue/digital/NMEA0183 to NMEA2000 system, and since I'm going to install it at the e/r picking up info from the rudder sensor, e/r temp, exhaust elbows and a few more, I may as well "waste" 10 inputs in order to get 10 wires out of a ribbon measuring open/closed circuit and process the info in arduino. Piece of cake (programming wise) maybe an issue managing to stuff a ribbon down a metre long 15mm transparent flex tube without it coming in front and messing with the visual checking of level. Maybe rolling the ribbon up round a small plastic stiff rod is the way to go.
BTW, would such a system work for diesel as well? Also got 1.1m high diesel tank again with a sight gauge.
Are there any other resistive methods of measuring levels that could be hooked to an analogue input of an arduino I wonder!
cheers
V.
Actually since I just managed to sort my arduino analogue/digital/NMEA0183 to NMEA2000 system, and since I'm going to install it at the e/r picking up info from the rudder sensor, e/r temp, exhaust elbows and a few more, I may as well "waste" 10 inputs in order to get 10 wires out of a ribbon measuring open/closed circuit and process the info in arduino. Piece of cake (programming wise) maybe an issue managing to stuff a ribbon down a metre long 15mm transparent flex tube without it coming in front and messing with the visual checking of level. Maybe rolling the ribbon up round a small plastic stiff rod is the way to go.
BTW, would such a system work for diesel as well? Also got 1.1m high diesel tank again with a sight gauge.
Are there any other resistive methods of measuring levels that could be hooked to an analogue input of an arduino I wonder!
cheers
V.
Hydrozoan
Well-Known Member
Sorry, I forgot that you, not vas, had asked the original question when I added the footnote - duh!
My tank is a lot smaller (ca. 120l) so a cumbersome group of separate wires did not appeal to me. You might also find the resistance of a longer length of ribbon cable too much - mine is about 40cm in the tank plus a metre or so to the Kemo unit - but you could try it. Or Norman_E may have another way.
PS In answer to vas, I doubt it would work with diesel - and perhaps it might struggle more with a soft water's lower conductivity - I'm afraid I don't know offhand the conductivity or hardness of my marina supply.
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nigelmercier
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I imagine that you could calibrate this by positioning the senders at appropriate heights. My original sender was a bunch of five stainless rods, giving four levels. The system was never very reliable, and almost iimpossible to fault-find on.
Norman_E
Well-Known Member
I lost this thread for a while. I am planning a little article for PBO. My sender consists of a length of plastic drain rod into which I have screwed 11 small brass screws as terminals for the eleven wires. The rod is mounted by means of an angle bracket bent up from stainless steel, and bolted to the tank lid.
Norman_E
Well-Known Member
I am not sure what you can do with the arduino but its no good just feeding a low voltage into the wires and expecting clean water to conduct electricity. You actually need eleven wires to get 10% readings. The bottom one is the "earth" and the other 10 give you the outputs. I think the Kemo gauge probably feeds some sort of higher voltage or frequency into the wires to ensure that a signal current gets through the water. The gauge will show as empty when the 10% terminal is above water. On my Kemo gauges this is actally when there is about 2.5 inches of water left in the tank.
vas
Well-Known Member
was thinking about that, but found a bamboo watering arduino project that was using this exact method.
Granted pumping a whole of 5V and hoping to pick something on the other side is not ideal, but if I have some time i'll test it soon.
Again since the tank is about a metre high, I was thinking that maybe get the 10 wires down the tube and have at 10mm distance a ss rod as cathode (or anode whatever...) so at any given wire the current only has to cross 10mm or so to be picked up from the other side. I know the problem is how to make sure that this assembly wont short on the spot or after some shaking about. Maybe some sort of spacers could be employed.
any ideas?
V.
nigelmercier
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To those considering sensors that measure the water resistance, I have the circuit diagram of the one originally fitted to my boat if anyone wants it. Secondly, do make sure you only energise the sensor when taking a reading.
Hydrozoan
Well-Known Member
Yes, with the Kemo you press a button to get a reading. Norman is right to point out 11 wires with the return, not 10 as I said - my return was also one of the ribbon cables. I did warn about the resistance of the cables, and that I didn't know how well it would work in very soft water; but if Kemo's illustration was of a rainwater butt, I guess it's OK - albeit perhaps with better contacts than my ribbon cable.
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affinite
Well-Known Member
I have an existing resistive sender in my fuel tank but the display (LED bargraph) has failed
I am using a Raspberry Pi for navigation and have added a MCP3208 connected to the old sender and python script to measure the fuel tank depth
I can read the sender very acurately but dont yet have a decent guage to display (Its WIP)
http://www.raspberrypi-spy.co.uk/2013/10/analogue-sensors-on-the-raspberry-pi-using-an-mcp3008/
nigelmercier
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A couple of requests for this, so ...
[1] Go to the Bavaria Yacht Forum
[2] Click Downloads on the link bar near top of page
[3] Download the file Bavaria Panel PB-42 (Water Gauge and Terminal Block)
This file contains schematic diagrams and PCB plan of the original gauge electronics, pictures of the PCB and sensors, and anything else that is related to this circuit.
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