Bradley Worley about
The thermy digital thermometer My first microcontroller project


Before this project, I had very little electronics experience. My only time spent was with an RS232 interfaced servo controller, which was canned and plagued with good luck in the form of complete functionality. (You never learn anything when something works.)

To put this project in concrete context: I learned about Ohm’s law when I started sketching the resistor dropper circuit connections for the LED displays. Elementary stuff here.

First design

My first design never actually saw production. The layout had fatal flaws that would have made it absolutely non-functional, specifically the LED directionality and footprints. Thankfully, I figured that out without ordering the boards.

Second design

My second design did see the light of day, but mostly failed. The DS18B20 just overheated and I decided to re-design the board instead of fix any other problems and ignore the sensor.

Final design

Finally, I built a board that could be programmed and would write readable numbers to the LED displays, but the DS18B20 was still overheating. Thanks to the patient aid of AVR-Freaks members, I learned that the sensor was wired backwards! It turns out the datasheet shows a bottom view, and I missed the fine print indicating that fact… D’oh!

Design files

If you’re interested in looking at my designs, for whatever reason, here they are. The last file is what I used to make a TO-92 footprint for the DS18B20; it’s a total hack-job. You’ve been warned…

Project images

The original web page for this project was just a thumbnail gallery, so most of the information is spread through a bunch of image captions. For your viewing pleasure, here are the remaining images I captured to document my progress on thermy: