Finishing Up The Color Thermometer

 

In the last post I looked at building a thermometer that showed the temperature and humidity of a room through the use of a color display that indicated the relative comfort level of the room, using an Arduino and a couple of extra components. 

While the thermometer worked quite well, it really did just look like just a bunch of wires that glowed. To have it be part of polite society, it needed to be dressed in more appropriate attire. 

Since the circuit is a fairly compact design, the thermometer would lend itself well to being housed a fancy box that could look pretty sitting on a shelf. On a recent clean-up of the shop I noticed that I had few pieces of red cedar and popular sitting in the scrap bin.  I always liked the look (and the smell!) of red cedar so I always try to avoid throwing of it out on the off chance I had use for it. As luck should have it, the scrap pieces looked to be a good size to house the Arduino. 

Designing The Case  

With my source materials acquired, I set about designing my enclosure. Basically the enclosure had to:

• Of course contain the Arduino, Temperature sensor and the LED strip.
• Have a way to mount the LED strip so that it seamlessly integrates into the case
• To do that I decided that the case should have a slot cut into it to mount the LED.
• To add a bit of a diffusion to the LED's the slot would also be cut to accommodate a plastic strip to mount in front of the LED's 
• Provide proper air flow so that the temperature sensor can properly detect the room conditions
• Be simple, basically the case should just be a your basic box.

With the criteria defined and based on the wood I had on hand, I sketched out a quick design

Bill of Materials 

• Two 1x4x6.5 inch pieces of popular
• Two 1/4x4x6.5 pieces of red cedar
• One 1/8x3/4x6.5 piece of clear acrylic 
• Frosted glass paint
• Wood glue
• Furniture felts
• Small rubber grommet

Tools Required

• Table saw
• Router with a 3/4 inch straight bit
• Wood clamps
• Drill Press
• Glue

Case Assembly

I started off by cutting out the 4 pieces of wood that will be used to make up the case

Next I marked out the cavity that will be used to house the Arduino and sensor on the two popular pieces and routed out the cavities

Once everything was cut out, I then glued the two Poplar pieces together along with one of the Red Cedar pieces (which will serve as the top for our case)

 Once the glue hard dried. I next had to put in a grove near the top of the case. To do that I took a 3/4 inch straight bit on my router and I cut a 1/2 inch deep groove about one inch down from the top of the case along the front. This groove needs to be deep enough to accommodate the LED strip and the 1/8 inch thick acrylic strip. 

One problem that I found with the groove is that I did have it come out of the sides of the case which didn't really look very good as far as I was concerned so I really wanted to have it look a little bit better.

To solve that I cut out and glued in a couple of red cedar "plugs" to fill the ends of the grooves but still left some space on the end for the acrylic strip to be flush against the front of the case. 

At this point, the main part of the case is now assembled. 

Perfect time to give every a quick sanding to neat everything up. 

With the groove in place I next cut a 3/4 inch wide strip of acrylic and cut it to the length of the case.

After a quick test fit to the case (and some trimming to make it fit better) I then gave the strip a coat of glass frosting paint to get a more diffused look when the LED's are lit. 

To complete the construction of the top part of the case I finished off by drilling in a few vent holes so that I could have some air flow for the temperature sensor.

Installing the Innards 

The next step in the process was to put all the electronic bits into the case. I started off by looking at what would be best way to mount the Arduino.  To do this, I decided on mounting it to the remaining piece of red cedar that I hadn't yet glued to the case. 

After doing a test fit of the Arduino to the bottom plate I determined what would be the best place to mount the Arduino I then cut out and glued a couple of wooden rails to the red cedar, which would serve as a mounting point for the Arduino. 

Once the glue dried, I then mounted the Arduino to the base with a few screws.

The next thing to do was to mount the temperature sensor into the case. Since I drilled the ventilation holes into the top of the case, it makes the most sense to have the sensor mounted as close as possible to the vent. To do this I glued another small wood block to the top of the case and attached the sensor to the block.

Finally I mounted the LED's into the groove that I had earlier cut, luckily the groove also opened up an access to the internals of the case, so the wiring for the LED was pretty easy to feed through 

I glued the LED strip in place followed by the acrylic strip 

With all the various components mounted the next step was to wire everything up and buttoning up the case. 

One thing I failed to note was how I planned to power up the Arduino once it was sealed up. 

To power the Arduino, I chose to power it through the Arduino's USB connector, which will also give me an opportunity to do any tweaks to the programming that I might want to do in the future. 

To provide power access, I usually would drill a half inch hole into the back of the case, but as a lucky coincidence, one of my popular pieces had a knot that popped out that was the ideal size. So I fed the USB cable through the knot hole and used a rubber grommet to neatly cover the hole.

 Finally I glued the rest of the case together

I finished up the job with some varnish and after installing some felt pads on the bottom, the project is done!

At the moment the thermometer is still on my desk here at work giving my a nice visual interpretation on the office climate.  It's certainly been a bit of a conversation piece. 

Next month, I going to revisit a topic that I first posted about a few years ago.