Arduino Tank/Battery Monitor

[Zeppelinium]

This post is just a place holder until I can document the prototype in the photo below. Total cost is about $40, plus your time to install it and maybe run the additional wires for the temperature sensors.

"Arduino" is the name of a family of small microcomputers that are super easy to program and use. Setting up the display and sensors in the photo below took about 30 minutes, including downloading the software and modifying it slightly to provide the appropriate display text.
Z

PS--this monitor uses waterproof temperature sensors, so you can make a monitor to show the temperatures inside, outside, in the tanks, behind the cabinets, in the water heater, in the fridge, in the freezer, in the fridge chimney, in the air conditioner, etc. You can show 8 temperatures, each with a short label, on this 4x20 LCD, or more if you don't think you need to label each reading. If there is interest in such a device, let me know. I intend to install one in each of my Airstreams, particularly the fridge monitor capability.

[Linus]

Amazing! Id never heard of Arduino, looks like a great addition to a trailer. Are the temperature and fluid level sensors separate from one another? Are they wireless? Looks like you've included an amp meter as well, does Arduino make a shunt? Is the monitor switched? Great work, thanks for sharing. I look forward to future posts on the subject.

[Zeppelinium]

The current sensor is an Allegro ACS712, 30 amps. It has an internal resistance of 1.2 milliohm, about the same as the copper shunt in the old Univolts. The advantage of this device is that zero current produces an output of 2.5 volts. Zero volts is negative 30 amps and5 volts is positive 30 amps. The analog input on the Arduino can read this directly. The old shunt system produced a negative voltage for negative current, which is harder to handle in a digital system.

Battery volts are measured directly by an analog input on the Arduino.

Temperature is sensed by DS18B20 one-wire sensors that are accurate to +/- 0.12 degrees C. These can be water proof and submerged in the tanks or placed inside the fridge/freezer, as well as outside.

Tank level is more problematic. The initial design will use the vintage system of probes and wires to detect fluid level. I haven't decided yet whether to show that using LED bars or on the screen. I'd prefer to keep the screen area for temperatures, amps, and volts.

Z

[65CV]

Zep-

Great find -- not only on the microprocessor -- but on the sensors as well. Looks like a great way to have a small, discrete monitor for a host of different applications. I predict that we'll see some very creative uses in this thread.

Here's one idea: since you seem to be into the '70s era, are you thinking about programming a motion-activated disco ball?

John

[Aviator]

I am interested in such a device. One for the full on 1970 Restoration I am involved in and one for out 1997 on which none of the probes currently work. I have been using a standard La Crosse inside/outside temp display for the fridge by simply placing the wireless sender inside the fridge. Having a couple of central displays would be great. Possibly one for fluid, propane levels, and battery condition with the other dedicated to various temperatures.

[wxbuoy]

I am interested as well! I am at the point in my rehab to install or run wires if needed. Looking forward to details, schematics and parts list!

[VSpeck]

Originally Posted by Zeppelinium

Tank level is more problematic.

I dont know if it could be used in your setup or not but on my Arduino computer that I use to monitor and control my aquarium there is a level sensor that uses pressure to monitor the level of the aquarium. Basically it is a sensor in the top of a piece of pvc that monitors air pressure in the pvc, as the level goes up it compresses the air at the top and tells you that it is full. I am new here and don't know the exact rules about posting links to off subject sites but I can post if its ok. I have no affiliation with the company I just thought it might help. Also there is 15" of range on the height of the water I don't know if that's enough or not.

[Zeppelinium]

VSPECK, post away. Any input is helpful to the discussion. Sounds like your sensor might fill the bill. We only need to measure 7" of depth. The only problem I can see is that sloshing in the tanks may allow fluid to get up to the sensor and wet it. It is obviously not designed for that.

Z

[VSpeck]

there is no good way to ling directly to the module but if you click the link and then click expansions it under water level expansion module. Sloshing tanks shouldn't be an issue. I mistyped the last post. In the top of the pvc is an adapter that a piece of 1/4" air line connects to and that connects to the sensor. The actual sensor its self can be kept well above the tanks and in a safe and dry space. The same company is working on a 5port level sensor which would be more helpful in our situation but if you are good with hardware work you could make a 3 port or whatever you needed I'm sure.

here is the link to the company page
Reef Angel Aquarium Controller

the same company has humidity expansions and leak detectors and waterproof temp probes and everything. Maybe it would help you in designing your setup.

[garry]

Here is a tutorial for anyone looking for "how to" information with the Arduino.

Arduino Tutorial - Learn electronics and microcontrollers using Arduino!

[Chillpoints]

Thanks for the new link

[Zeppelinium]

Originally Posted by VSpeck

there is no good way to link directly to the module ...

here is the link to the company page
Reef Angel Aquarium Controller

the same company has humidity expansions and leak detectors and waterproof temp probes and everything. ...

I've searched for a suitable device and the MP3V5100 is about the best I've found so far. It's a +/- 0.3 psi (gauge) transducer for about $14 in single units from Digikey. The vendor (Freescale) makes all kinds of these chip-based transducers. This unit puts out 2.5V at zero pressure and 4.5V at 0.3 psi (only the positive pressure output is useful in this application). For almost all tanks in vintage Airstreams, the max tank depth is less than 8". Eight inches of water is almost exactly 0.3 psi.

The problem is, how to connect the sensor to the tank. The fish tank example above is nifty in that keeps the sensor dry and re-zeros itself every time the tank is empty, but it requires a vertical intrusion into the tank.

Zep

PS--this does the same thing as the $70 unit from the aquarium company, but you have to be able to solder the surface mount package to a circuit board. It's a challenge.

[VSpeck]

Originally Posted by Zeppelinium

The problem is, how to connect the sensor to the tank. The fish tank example above is nifty in that keeps the sensor dry and re-zeros itself every time the tank is empty, but it requires a vertical intrusion into the tank.

I didn't know if there was a way to get in the tanks for you other than a major renovation situation or not.

Originally Posted by Zeppelinium

PS--this does the same thing as the $70 unit from the aquarium company, but you have to be able to solder the surface mount package to a circuit board. It's a challenge.

Yea I'm sure there are ways to do it cheaper but by going through them I get a whole forum full of people working on the same situations as me and 24hr customer support and its already built. I could solder and assemble but that's more work than I want to invest on that particular hobby. I already have enough time in reef tanks

[Wayward]

Very intersting stuff.

Parallax sells a 12" submersible strip that converts pressure changes to variable resistance.

Here is an 8" version that looks similar

Here is a video with some Arduino code to read the resistance.

Someone else suggests using a Parallax ultrasonic sensor and converting ping return time, to distance. Code is here but it is not clear if anyone built it.

Garnet's SeeLevel sensor seems to attach on to the outside of the tank. It might be using 1-wire technology with a proprietary data format. This would be an interesting Arduino hack as the sensors can be purchased separately.

[Zeppelinium]

Originally Posted by Wayward

...
Parallax sells a 12" submersible strip that converts pressure changes to variable resistance...

Darn, I had seen this before and completely forgot about it. ...too much going on...

Thanks for the point outs. Very helpful.

Z

[garry]

Just thinking out loud here but I would think about mounting this close to the tank on it's own PCB and just run wire to the Arduino.

One thought is to put a tee (3 way) shark bite in the input line to the water pump run a clear plastic water line from the T down into the tank. A small line like the water line in the in a ice maker should not interfere with the pump operation.

[barts]

I'd looked at those level sensors from SparkFun earlier....

The easiest way to plumb one in would be in PVC pipe, with hoses going to the bottom pump suction line and a (small) connection to the tank vent line.
On my 1971 this is not much more that 1/4" tube, but we just want the water level in the sensor to match that in the tank.

In terms of displays a bar graph for the level seems nice... but I really like numbers on things like voltage and current.

- Bart

[Zeppelinium]

Originally Posted by garry

...
One thought is to put a tee (3 way) shark bite in the input line to the water pump run a clear plastic water line from the T down into the tank. A small line like the water line in the in a ice maker should not interfere with the pump operation.

Sometimes it's not so easy. If you are using air to transmit the pressure from the tank to the sensor, you have to be sure that at zero pressure (tank empty) the line has no water in it and that for at least the height of the tank, the line is pretty much vertical. Any water in the line at zero pressure will subtract from the tank pressure.

It's the principle of the diving bell or putting a glass upside down in water. As the glass is pushed downward, water pressure begins compressing the air and some water begins to creep up the inside of the glass, but the air will be at the pressure of the water at the bottom rim of the glass. But if you have an inch of water in the glass before you push it down, that inch of water pressure is always subtracted from the actual pressure. So you have to have a design that insures that the tubing never has water in it when the tank is empty.

This is not a problem for the sensor that BARTS suggests because he is using the type that is submerged. He maintains the water level even between his external tube and the tank by attaching the tube to the bottom of the tank and to the vent.

Z

[Panama Red]

Could you achieve the vertical intrusion by dropping it down the vent stack? My center bath has vertical stacks on both gray and black tanks... Relatively easy access to both. Just an idea.
-Red

[Zeppelinium]

Originally Posted by Panama Red

Could you achieve the vertical intrusion by dropping it down the vent stack? ...

Exactly, but I'm wondering how you would secure the tube inside the stack. I'm also not too fond of opening the black stack.

Before we all get too wrapped around the axle, this is a great discussion, but the first version of the monitor will use the old probes in the side of the tanks. It will be able to use the early 70s 3/4-wire versions or interpret the 2-wire later 70s version.

Z