Arduino Tank/Battery Monitor

[Zeppelinium]

It looks like all the functions mentioned earlier will fit on a 2.3 by 3.7 pcb. This includes connections to the LCD display, three tank levels, one discrete temperature, battery amps and volts, and multiple digital temp sensors. Note that tank levels are shown on LED ladders.

Z

[Zeppelinium]

Monitor is up and running. Not finished, by any means, but the basic interfaces and connection to the LCD work. The unit as shown below is 5.5" wide by 2.75" high. The format of the display is totally reconfigurable; current display is battery data on the top line, then two lines of inside and outside temperatures with their min and max, then the bottom line with fresh tank water temperature (in case you want to activate the anti-freeze valve, which is a 1/4" solenoid water valve from the hot water line, about $12 from China) and fridge temperature.





The tank levels will be shown on three LED ladders ( or two if you have a pre-75 Airstream) to the immediate left of the LCD. The resolution for each temperature display is TBD--there's not much reason to display to hundredths of a degree, except maybe for the fresh tank if you're camping below freezing. It would be nice to accurately estimate the rate of change of water temperature to predict when you might need to do something.

The mechanical mounting, relationship of the Arduino board to the LCD, and some of the small spacing on the Arduino board are not in concrete. Expect some changes in these areas.

If you have input, now's the time to make it.

Once the boards are finalized, they will be available from OSHPARK.com, minimum order of 3 boards in increments of 3, for about $35/three. If you're interested in a single board, let me know now so I can order them when I do the update.

The software is modified C code for the Arduino. You can download the developer environment for free from Arduino IDE. Go to the download tab to get the software. I'll make the basic software available at AirstreamDoctor.com if you want to write your own custom display. If you have the IDE, you can reprogram the Nano board with a USB cable. Dead simple.

Zep

[Zeppelinium]

The LED ladders do the trick (IMHO). I'll get a nice bezel made (laser cut) with holes for the LEDs and labels, plus a place for the water pump switch and I think it will be a complete prototype.



The LCD limits what can be done, as far as different data. This unit has the capability to read other voltages, other temperatures, but they couldn't all be displayed simultaneously. Maybe multiple display pages are in order (air conditioner in/out temps, two temperatures in the fridge, outside shell temperature (of interest when you're in Mojave in the summer), etc. A push button switch could change pages...

Zep

[cwf]

Most excellent!

[Chillpoints]

Are you sure you don't want to sell them? I for one would be interested. It looks great. Well done.

[wxbuoy]

Originally Posted by Chillpoints

Are you sure you don't want to sell them? I for one would be interested. It looks great. Well done.

Ditto!

[Zeppelinium]

Originally Posted by Chillpoints

Are you sure you don't want to sell them? I for one would be interested. It looks great. Well done.

I may go so far as to make up some kit instructions. When I get time to do the bezel you'll see the possibilities, eg, LEDs on the left as shown in the photo, or LEDs above or below the LCD display. Also, need to add a spot for the pump switch.

On another note, I was reading Tim Kendziorski's article (I think it was in the VAC, or maybe the Blue Beret?) on how the fridge works, and realized that if you had some decent temperature readings from the chimney behind the fridge, you could activate a fan or a louver to significantly improve fridge performance. So having an additional page of data (and a switch to get you there) would be very handy.

Zep

[barts]

I wonder if a solution to the display issues isn't to use a Raspberry Pi configured as an access point... you can then use any smart phone or tablet as a display device.

I think the Arduino is neat - but pixels count.

- Bart

[Zeppelinium]

Originally Posted by barts

I wonder if a solution to the display issues isn't to use a Raspberry Pi configured as an access point... you can then use any smart phone or tablet as a display device.

I think the Arduino is neat - but pixels count.

- Bart

That's a great idea and we all eagerly await your long thread on developing the interface! All of us, that is, who have a smart phone. Mine is dumb as a Princess Phone. Z

[chromis]

Been looking at the Arduino yun ($72).
Arduino - ArduinoBoardYun

Also was testing a DIY tank level sensor using a capacitive sensor.
https://www.sparkfun.com/products/9695

Works but need to figure out tuning for charge/discharge and pad size for thick plastic. ( Yea seelevel .. DIY is for ego )

My initial test was with aluminium foil tape which worked reasonably well..
bildr » Sensing Capacitive Touch – MPR121 + Arduino similar to this guy.

But assuming I'd print a flexible circuit board and Stick it to the tanks externally. Using laser printer toner transfer..
DIY Flexible Printed Circuits

Also not sure about I2C/2-wire and distance over 10-20+ feet.
might have to consider rs485 adapter(s)..

[Zeppelinium]

Originally Posted by chromis

Been looking at the Arduino yun ($72).
Arduino - ArduinoBoardYun

Also was testing a DIY tank level sensor using a capacitive sensor.
https://www.sparkfun.com/products/9695

Works but need to figure out tuning for charge/discharge and pad size for thick plastic. ( Yea seelevel .. DIY is for ego )

My initial test was with aluminium foil tape which worked reasonably well..
bildr » Sensing Capacitive Touch – MPR121 + Arduino similar to this guy.

But assuming I'd print a flexible circuit board and Stick it to the tanks externally. Using laser printer toner transfer..
DIY Flexible Printed Circuits

Also not sure about I2C/2-wire and distance over 10-20+ feet.
might have to consider rs485 adapter(s)..

now you're talking! Great inputs.
Z

[rasjad]

Check out this unit - it uses a "field-effect" sensor to sense the water level from the outside of the tank. I installed one of these on another trailer and it seemed to work fine. Looks like you can buy the sensors alone for $30. Might be fun to try.

SensaTank II Fluid Monitoring System with Field-Effect sensors

Rasjad

[Zeppelinium]

Originally Posted by chromis

...
Also not sure about I2C/2-wire and distance over 10-20+ feet.
might have to consider rs485 adapter(s)..

I have four (4) I2C sensors on 20' or longer leads that have been operating for more than a month in an unfinished house environment. No problems so far.

Rasjad, I looked at your suggested sensor. It seems to work like the penetrating contacts, except no penetration. I prefer to use a continuous sensor. The Arduino community has several methods of achieving this. You can start by looking here. Also, the Atmel microprocessor handbook has a capacitive sensing application.

Zep

[chilipepper]

I've been watching this thread with great interest and have been playing with some ideas to add to the info here and try and retain some of the vintage look. So I've been playing with the small stepper motors that are used in automotive gauges made by Switec. I've mocked up a very simple circuit with 2 LM34 temperature sensors. I also printed a quick dial face and cut a pointer out of paper just for proof of concept. It works pretty good. I need to add a switch and then you can toggle between the 2 temp sensors (indoor/outdoor). The LED will light when you are on the outdoor sensor and shut off when on the indoor.

I'm thinking the temp dial could pretty easily be retrofitted into the old Springfield gauges that are in my '71. I'm pretty sure both are toast anyway. The barometer is for sure.

Zep, thanks for the spark to start tinkering with this. I'd like to look at your code and see how you have the connections made for the LCD and the ladders LED's. I'm thinking I'd run out of i/o lines on the standard Arduino and may have to go to the mega to make it all work. I'd also like to see what you did for battery monitoring.

[Zeppelinium]

I used ten I/O lines to address the LED ladder. Two of the ladders always have the base LED on, so they only need three lines each. Right now the lgic escapes me.

In order to monitor the tanks using the standard "pins in the tank" system, you need an off-board resistor ladder for each tank in order to scale the voltage for input to A0-A2.

The battery voltage is monitored directly through a 1/3 voltage divider. I had considered using an offset scheme, but 10 bits is enough resolution to provide 0.05 volt precision in the 11.0-14.5V range. Current data is provided by a 30A hall effect sensor. You can find these dandy devices just by Googling "Arduino current monitor." I have this one and several others.

Connection to the LCD is through the SCL/SDA lines (A4-A5). You need to buy the LCD with the 2-wire hardware driver.

As you can see, the Nano can handle all this with D0-D1 (Rx/Tx), D12, D13 (if you can abide the LED on that pin), and A3 to spare.

This is a very preliminary board--just wanted to see if it could be done. I'm still toying with the idea of putting all the data on the LCD and not having an LED ladder.

Zep

[ericgu]

Hi,
Very interresting project. I'm looking to do the same prototype for my camper.
where i could find more info?
Thank you

[BoldAdventure]

Dang, I was toying with building a Pi for the Airstream, but this is even more interesting.

[BearScream]

Just found this eye-opening project. Ingenious work, Zep. Thanks for the trip.

[flaagan]

Just something to toss out, maybe to add some kind of "exterior light controller." I grabbed the daylight sensor off the Pontiac Solstice I'm using as a parts car for my Morgan project. I believe the thing runs off of a 12v system with some kind of resistance based on light detection (could be wrong, haven't had a chance to mess with it yet). The idea being, you could use it to automatically turn on exterior (or interior) lights based on lack of daylight, with a programmed in cutoff / turn-off point to play along with park 'lights out' rules.

Just a fun idea.

[ArtisanAir]

I too have a good background with this technology! I've been toying with these things for about 2 years and there is almost an unlimited amount of things you can do with it. I personally installed one in a 2000 Honda Civic DX. Let me finish... This Honda has a lot of custom things done with it all done by myself, let me get to the topic. I installed two Adruino systems, one consistently running (UNO) and the other when the car comes on (MEGA).

The UNO is equipped with a GPRS shield (laymen terms a cell phone without the screen or case). I then wrote logic to accept a text from my personal cell phone only and start my vehicle from anywhere in service range. It would then reply a message back when sensed voltage reached over the 13.7 VOLT running alternator state. The GPRS shield had to be linked to a AT&T account and assigned a cell phone number. You could also "kill" the engine and keep it off when you feel like it is necessary, or just send a stop run command with the ability to be restarted originally.

The MEGA is instructed to turn on with the ACC status is initiated. This module controls all of my climate controls. I normally run logic that simply attempts to reach a desired temp (72) by increasing or decreasing the temperature in the cab. Once the temp is reached it slowly ramps the fan down within 3 minutes time until blowing softly. I also have a 10.4 " touch screen running a Windows-base GPU that can control any aspect of the climate control system (not really needed when done automatically but still nice).

I know what you are thinking, this is stuff that is equipped in most vehicles, but remember the beginning of this ramble, this is a 2000 Civic. They weren't even thinking about that stuff back then. I want to help any way possible with knowledge with this equipment and the endless sea of sensors, actuators, motors, on and on. I do believe I could even possibly be its own forum or sub-forum one day (popularity is increasing drastically). I love the fact that people are already interested about them in RVs. Your mind will race after doing research about the capabilities! Please if any questions please feel free to ask!

P.S. the logic is the magic that sets apart people from the rest I went to Miami University of Ohio for Computer Science.

These pictures are the UNO / GPRS Shield / Relay Shield = car starter!