Automotive Tire Pyrometer Project
By Daniel Hankewycz, Mouser Electronics
Licensed under CC BY-SA 4.0
Assembly
Step 9: Assemble PCB
Once all the hardware and software has been finalized, it is time to set this project in stone... or solder. I
chose to make a custom PCB since my university has a CNC isolation mill, but there are plenty of other options
as well. Mouser sells PC prototyping boards that allow you to solder the component together with. The benefit to
this (http://www.mouser.com/ProductDetail/BusBoard-Prototype-Systems/SB1660/?qs=sGAEpiMZZMtgbBHFKsFQgo04jOHntgNPR1pgBh9E9%252bI%3d)
specific protoboard is that it has the exact same layout as a breadboard, so most of your circuit will be a
direct crossover. All source project files are located in the Resources section so anyone can make the exact
same board that I made.
Step 10: Building the Tire Probe
In order to measure the temperature of the tire properly, pyrometers usually use probes that have a sharp tip.
This allows the thermistor to measure the internal temperature of the rubber, since the surface usually cools
quite quickly. Considering that I can't put that much pressure onto the thermistor itself, I had to find a way
to attaching some type of metal extension to it. I chose to use copper because it has a high thermal
conductivity coefficient, and it is readily available.
To make the probe, I knew that I would have to make a good thermal bond between the thermistor and the probe
material itself. After numerous attempts, I finally settled with the materials as shown above. I went into my
scrap bin, and pulled out a few inches of 12AWG copper house wire. I then used a hammer to flatten one end of
the wire until it was nearly paper thin (surprisingly easier than it sounds). Once I had the one end flattened,
I used something similar in size to the thermistor to roll the copper tab into a hollow tube. I then used some
sand paper to grind off the excess copper on the ends, and then filled the hollow tube with thermal paste.
Lastly, I put some heat shrink tubing around the entire thing just to make sure that the thermistor and paste
didn't fall out. This process resulted in a nearly continuous thermal connection from the tip of the copper to
the thermistor itself.
Step 11: Enclosure
The last step to this project is to put the pyrometer into some type of enclosure. When it comes to choosing an
enclosure, I always focus on a few key features:
- Power source: placement, thermals, size, etc.
- Type of Material: How harsh is the environment?
- Dimensions
- PCB mounts
- Application-specific requirements
In the case of this project, I wanted the pyrometer to be powered by common household batteries: AA, AAA, or 9V.
I decided to use AA batteries because they cost less than 9 volts, and I already have a bunch of rechargeable
AAs. Picking a size for the enclosure was difficult because I had to choose something wide enough for the LCD,
but I also didn’t want it to be too thick to hold comfortably in my hand. Next up is choosing a material. ABS
plastic is typically a good choice because it is soft enough to cut with a dremel tool and small files. Lastly,
I knew that I wanted some way of mounting the PCB inside the case. This enclosure used standoffs to suspend the
board, but some enclosures use slots or grooves to hold a PCB. Mouser provides a wide variety of enclosures to
choose from, so finding one that fulfilled all these requirements was a walk in the park.
