Posted 17 August 2024

Long ago and far away (at least 2m) I designed and built a small temperature humidity display for my plastic bin filament dryer setup, as shown in the following photo:

This worked well, but the display wasn’t very readable, especially through the side of the plastic bin. In the years since then I also did a digital real-time clock display project using the much nicer ILI9341 TFT display. I have a couple of spare displays and a couple of Teensy 3.2 units lying around, so, I decided to upgrade the temp/humidity sensor.

The schematic for the Digital Clock is pretty simple:

As was the breadboard:

So, how hard could it be to use the same setup with the RTC replaced by the original Adafruit-DHT22 sensor

Probably have it done by tomorrow – yeah, right!

18 August 2024 Update:

Well, I don’t have it done yet, but I Have made some progress. I dug out one of my spare displays, a Teensy 3.2 and may small plugboard and wired them together using the schematic from my digital clock project. And, amazingly, it all went together quite nicely. I loaded up the ‘graphicstest’ example from Paul Stoffregen’s ILI9341_t3 library, and damned if it didn’t work right off the bat! Here’s a short video showing the action:

That is a huge step in the right direction for this project. Now all I have to do is add the Temp/Humidity sensor and code, and convert the sensor values to pixels on the screen – yehaw!

19 August 2024 Update:

I now have the DHT22 sensor integrated into the system, and have adjusted the display parameters for a nice ‘across the room visible’ format, as shown below:

Then I moved everything over to a more permanent prototype board, as shown below:

21 August 2024 Update

After a lot of quality time with OnShape, I created a nice bezel to go around the display, and a nice box to go around the whole thing

And here is a photo of the completed project. The temperature and humidity seem to have stabilized at about 87ºF and 33% RH.

Stay tuned,

Frank