Room Temperature Sensor; got to use the 3D printer for real

I used my 3D printer on a real project, the room temperature sensor. I spent a ton of time messing around with various drawing tools and learning a little about slicing software, but didn't actually do anything that could be considered useful. Unless you count a stand for my Star Trek Enterprise that I have on the kitchen window sill:

I got the files for the stand off Thingiverse <link> and just printed it. Thingiverse is wonderful for getting things that other people have worked on, but it isn't the same as coming up with your own idea and stepping through the entire process.

I decided on the basics of an enclosure for the sensor weeks ago, but it took a while to decide on a tool to use to design it, then the actual design process. I tested a couple of enclosure ideas for a few weeks and finally, a couple of days ago, put four more of the sensor electronics together and printed enclosures for all of them. I have five areas of the house being monitored and recorded in my home database that I can chart and examine.

Yes, they follow each other really well over the period charted, but remember, a temperature change of a small amount will make a room feel hot. It's interesting to watch this phenomenon. One room is 75F and the next is 78F, not enough to matter, but it feels really hot in the warmer room. It doesn't help much to put a thermometer in the warmer room so you can see the actual temperature; you just think the thermometer is wrong. Strange.

Here's what the entire assembly looks like on the wall:

It consists of a base plate that you mount to the wall and a cover that slides over the base to protect the wiring. Here's the two pieces before mounting:

Most of the engineers out there could have drawn this up in about 10 minutes, but frankly, this process was tough. Every little item had to be measured and thought out carefully. I had many, many test prints of sections to see if various things actually fit together. I kept running into little unexpected problems. The plastic would be a little too rough in some spots and pieces wouldn't fit together. The model would glue itself to the base of the printer and it flatly refused to come off. I didn't put holes in the sensor PC board and had to come up with a mounting solution for it. How tall EXACTLY should a stand off be for the various pieces?

Most of this stuff was trial and error. Lots of errors. Just look at the pile of various attempts that will go in the trash after I post this:

One thing I discovered towards the end of the project was that I could cut the model and only print part of it. That was a real time saver. I could print the section I was trying to settle on and test it without waiting hours for the printer to finish the entire thing. I didn't read about using this capability anywhere on the web. Lots of folk talked about cutting the model, but didn't mention how it could be used to test a section of it. I guess most folk use 3D printers to make single piece items.

It's surprising how many little things creep up and have to be solved. The battery holder:

was initially a bit of a problem. I didn't want to mount it flat to the base plate because the mounting screws would go through the plastic, so I put in a couple of standoffs for the two screws that go through the holes in the middle of the assembly. Of course, that made it rock on the screws when I messed with the batteries. I solved that by putting in four more standoffs that kept it from moving.

Th circuit board with the electronics on it didn't have holes for mounting screws (oops).

So I had to work out special standoffs that could hold the board in place. Of course I didn't have washers that would fit the standoffs, so I just printed them as part of the base. Here's what the base wound up looking like after I solved these problems:

The battery holder has six standoffs two of them for actual mounting and the others to keep it steady. The standoffs for the PC board have a cutout for the board and I use little washers to hold it down securely:

The little dark spot in the center-left is a moth that was attracted to the heat and became part of one of the sensors. Note to self: close the printer door stupid.

I slid the lid up on one of the sensors so I could show off the construction of the assemblies:

If you zoom in on the picture you'll be able to see the mounting arrangement more closely. They were simple to install since they only take two #6 drywall screws and the entire device doesn't weigh much.

This project has been a lot of fun over the last couple of years. Yes, YEARS. And it isn't finished yet. I still want to use the sensors to replace the two house thermostats by taking the readings of each room and turning on heat, cool, or just fans to control the internal environment. I want to chart the outside temperature along with the rooms to see how it affects things as the day passes from season to season (notice, I only have two seasons here: nice and too-darn-hot). I may even create outdoor sensors to measure the wall temperature on some of the outside walls. That will prove the insulation effectiveness.

Who knows what I'll do with this in the future.

I FINALLY Got My 3D Printer

Many, many moons ago I decided that I couldn't afford a 3D printer since I don't want to make 3D printing a hobby, I just want to design and print things to use in my other hobbies.

Things like a coffee cup holder for the little tractor, enclosures of one kind or another for the various little computers around the house, custom light switch plate that has a USB plug in it for one of those double outlets, an outside enclosure that will hold an XBee; you get the idea. I've spent hours scanning the web for ideas about enclosures and there just aren't many choices, and the choices there are, frankly, suck.

I don't plan on being the worlds greatest enclosure designer, but it would be great to hide the wires and switches inside something.

But, since it would be a tool, not the focus, I couldn't see spending over a $1000 for a reasonably good printer that I wouldn't have to babysit and nudge all the time. Since I wouldn't spend the money, I decided to use credit card points to buy the printer. It took years to get enough to buy the printer ! Those points don't add up very fast.

Once I got the points, I was up to my neck in various projects around the house that were causing me to spin in circles accomplishing nothing, so I decided to force myself to finish certain projects before I was allowed to order the printer. The well repair got in the way, I also got some very heavy duty shelves for the garage, some serious repair work on the pool filter, and a big storage box for my toy hauler, but I finally finished them. A couple of days ago, the printer arrived.

I got the Flashforge Dreamer basically because of the reviews. There are certainly better ones and cheaper ones, but at some point, you have to make a decision, and good or bad, this was the choice I made. Needless to say, when the printer arrived I unboxed it right away and hunted down the test print.

I did that! Sure, it was composed by someone else, and all I did was print a file, but after literally years of postponed expectations, I finally did it. Dual extruders and different colors of filament and totally enclosed, oh my. (misquoting Judy Garland in the Wizard of Oz a bit).

There's company visiting, so I don't get to spend much time messing with it, but I did create my first little box.

It's about the size of a quarter; too small to actually use for anything, but I drew it and printed it. No, darn it, it wasn't easy. I started off with FreeCAD and got totally lost in the intricacies and nit-picking of design rules. What the heck is a closed polygon anyway?

OpenSCAD is very compelling because you basically program the print. I could probably do that, but I really wanted to be able to just click on an object on the screen and move, stretch, or spin it until it looked like something I wanted to print. Lots of modelling software is geared towards creating characters for games. I'm not at all interested in the skin texture of some scantily dressed teenagers dream girl for a video game. Plus, that software is really, really complex. I want to print things, not spend weeks designing a facial scar for the burly hero of the latest version of Doom. On second thought, maybe the dream girl could be a project later.

In simple desperation I started using Tinkercad on the web. I'm not happy with it being a cloud based tool, but it will do for now. As I gain experience, I'll probably change to something else, but at least it was simple enough to get me started.

The box and lid above was done with Tinkercad. I got the box on the first try, and I based it on a box a friend of mine made me a couple of years ago. The lid, well that was another story:

The first one was too long, and I forgot a bevel. The second one was too long. the third wouldn't slide in at all, to big. etc. It took five tries to get it good enough. Now do you see why I started with a tiny box? I didn't use much filament (more is on order already) and I learned a heck of a lot. Plus, it didn't take five hours to print the thing. It's really disappointing to spend that much time and find out you missed the screw hole by 5mm.

The slide on lid is sort of the idea I want to use for my temperature sensors. Mount everything on the lid, screw the lid to the wall, and slide the box over it. Simple to mount, simple to open, and mounted to something so I don't keep knocking it off the bedside table. What else could I possibly want?

Since I've got relatives staying with me right now, I can't devote hundreds of hours to working out the details, but I can sneak in a little time now and then to play with it. It's funny they don't complain about the smell of melted ABS at all.

This area has an excessive heat warning for the next week. The local weather predicts temperatures as high as 120F (that's 48C to most of the world), so I guess I'll be inside for the afternoons.

Guess what I'll be doing.