Water is Life

First off, some old business from our last meeting to update you on.  I don't need to buy a new inverter.  This is both a happy and a sad time for me.  I don't like the inverter I already own.  But I don't really have the money to buy the one I like either.  So when I discovered the blown fuse on the cable between the inverter and the batteries I was relieved and bummed.  I am impressed with myself in one way though.  The fuse was 200 amps.  Easily the largest fuse I have ever blown in my life.  #goals. :-)

In other news I have spent the last couple of weeks working on improving my water system.  It is going to be a great move forward, but living through it has been a little more intense than I expected.

An Arduino sitting on top of some of my
retirement paperwork.  Sadly, I didn't
win though...

Let me explain it to you this way.  The van is 63 square feet.  A constant I have to live with. The water tank and its surrounding area comprise about six square feet.  Think about if a three week construction project came to your house and you had to give up ten percent of your space.  That ten percent happens to be where you store the bulk of your random stuff.  You have to fit everything currently in that area into your remaining space and incorporate it.  To you non-van-lifers six square feet is nothing.  It is only turning the numbers into percentages that gives it a sense of scale.

Starting out I had only one goal. I wanted to keep my water tank from freezing up. I learned the first winter living in the van, anything in direct contact with the floor is going to freeze.  I need warm air from the furnace passing between the floor and the tank to prevent that from happening.  I thought maybe it would work to just have an air gap.  Convection.  Over Christmas break I had the van home for a stretch of days and did the re-plumbing job I posted about.  Part of it was adding some foam blocks under the tank lifting it about an inch. No joy.  Maybe it didn’t freeze quite so easy but it has been a cold winter so it was frozen pretty often.  There was just not enough air movement.

To hook up the temperature probes I used a telephone
module available from Home Depot.  This allows me to
wire all the probes into one spot that can be disconnected
from the Arduino for service.

Casting around for other ideas, at first I was trying to come up with a direct solution. Thinking of ways I could pump direct furnace air to the tank via some kind of duct work. That always seemed too complicated. I started to think about something less direct.  Here is what I came up with.

I used an Arduino —what is called “open source hardware”. Arduino is classified as a micro-controller platform.  A very small programmable computer dedicated to a single task. Generic Arduinos cost $11.  To this I connected five temperature probes.  Why five?  That’s how many are in a bag for $7.  I wired to the Arduino a two channel relay, $4 and to the relay I attached a fan originally meant to be installed in a brand new Cray supercomputer. …Had its box been closer to the top of a pallet of fans, that's how it would have lived its life.  Instead the last box of twelve, the spares left over after the Cray rolled off the shipping dock, found its way into my hands via number one son.  Cost zero.  Finally I am an information geek so I bought a little OLED display $3 to tell me what the temperatures are at each of the probes and optionally the RPM speed the fan is turning.

To make the phone board work I had
to wire some jumpers on the back and
then covered them in a layer of epoxy.

About a twenty-five dollar investment. But with it and a little woodwork. I have built a system that takes air from the middle of the van and circulates it down  and around the water tank, its pipes and pumps.  This air only circulates when the furnace is running so it won't be a source of draft.  Pretty slick stuff.  This is how I built it…

First what I suggest is to develop some standards in what color of wires you use.  The temperature probes have yellow red and black wires.  But they are too short to be of any real value.  I extend them by using cheap CAT5 network wire.  I connect it to the probe using the following scheme:
Brown -> black (GND)
Blue -> red (+5v)
Orange -> yellow (data)
These are not random choices.  I might get into that in some later post but these colors correspond to POE or Power Over Ethernet standards that Voice over IP telephones use.  Using a standard like this will allow me to build on it and not worry if something random gets plugged into one of my wire jacks.

Starting out I used a small breadboard to get things tested
and working.  Then I wired it all to the Arduino.

Do I really need five probes?  Of course not.  I could have built the system using only two.  Only two temperatures are critical.  What is the temperature at the water exit (is it close to freezing?) and the furnace (is it running?). Beyond that it’s all just the cheap price of probes and my natural curiosity.  I will know about the temperature of the air at the intake of the fan system. The pump is the most valuable cog in the wheel so it seems a good idea to monitor its temperature as well. Finally just out of curiosity I wonder how really cold it is at the back of the tank, next to the outer wall.

The rest of the hookup was easy.  The fan, not surprisingly for a multi-hundred million dollar computer component, is pretty sweet.  It is actually two counter rotating fans back to back. Two fans in series, turning in the opposite directions, with fan blades mirrored of each other.  No vibration, very little noise, but lots of air movement.  The fans run at twelve volts and so that is why I use the relays.  The Arduino sends them a small signal causing them to switch and turn on the fan. 

Simulated furnace on with a probe laying
on my laptop.

I even got fancy.  If the temperature reading from the probe at the water exit is merely a little cold, only one fan comes on.  If it is freezing the balls off a brass monkey cold, then it kicks on the second relay to power the second fan motor.  I will some day take it a step further.  Another fancy feature of these fans is they are PWM (Pulse Width Modulation) fans.  Meaning I can make them spin at whatever RPM I want to just by sending them signals from the Arduino.  I can make them push exactly as much air as I need to without making more noise and draft than I really need to.

I have this whole system built, sitting on my desk at work.  The next step will be to get it installed in the van, a process I will be telling you about in a future post.

Here is the Arduino code I wrote to make it all work: