Comfort 5: Heat Faxer 1

This week's work isn't really about a separate theme of comfort, but I decided to use it to test a small part of pcb design for my final project (heat faxer).

Goal for this week: I wanted to try using ESP32C3 that uses DHT11 for temperature sensing if a "send" switch is on and warms up peltier module based on the temperature that is measured 5 seconds after the switch was turned on.

Recap from Week 2: The current plan is using a DHT22 (or DHT11) for temperature sensing, a Peltier module that heats up to the temperature that it senses when it receives data from temperature sensing through built-in wifi on ESP32C3. It also has an LED screen that if you want to send heat or not.

First, I gathered datasheets for the elements that I wanted to use (Here are the links to each components: ESP32C3 , DHT11 , CP14 (Peltier)). Afterwards I looked for other people’s examples of connecting ESP32C3 with the components. It was relatively straightforward to figure out ESP32C3 + DHT11 since it seems to be a common sensor.
While I was struggling a little bit to find how people connect Peltier to ESP32C3, I found this pretty helpful diagram from Arduino forum that shows how Peltier could be connected to Arduino using MOSFETs. (here is a link to the forum)
I learned Peltier components tend to run at a higher voltage and will need an extra battery to power it. In order to mediate between the voltage differences, the microcontroller (e.g., ESP32 or ESP32-C3) sends a low-power control signal to the MOSFET, which in turn switches the higher-power current needed by the Peltier module.

The open sourceness of kicad was attractive to me, so I decided to start with kicad and try SVG as well later. I also really liked the 3d view of the kicad. After having a rough idea of where things go, I put every compnents to Schematic Editor and used the examples as a guide to connect. At CBA office hour, Miana helped me with locating/finding right resistors and swapping out Peltier and battery with connectors as a place holder while I search for better parts + better reflection of the connections to PCB boards. Unfortunately I did not manage to document where things should go, but this is how the schematic design looked like after updating with Miana's feedback.

While still sitting in the CBA office hour room, I moved onto designing my PCB in the PCB editor. I did a practice using the example from the recitation, but I became overwhelmed by the amount of tangled lines and could not figure out where to even begin. Quentin came to the rescue and gave a few pointers on moving pin location around (using labels is super helpful with this) and placing components in a more strategic manner to keep lines more organized. We went back and forth between PCB and schematic editor to find the most reasonable composition, and this was how the schematic editor looked at the end.

This is how the PCB editor looked like.

This is how the 3D view of the PCB looked like. It is missing 3D models for some components at the moment, and I wanted to get an accurate dimensions to figure out how the container would look like. The Peltier and Battery will live outside of the container, so those are not needed at the moment.

After finding all the 3d parts for the components, I created a star shape as a celebartion. I found out you can make holes if you draw another shape inside of the outline of the PCB board.

I tried to challenge myself and make a finger shaped PCB board that allows the peltier component to be attached at the finger tip. Getting the finger shape was a chanllenge in kicad. I tried tracing it in Rhino and brought it back to kicad.

I added the cad file (exported from rhino) around the board. Unfortunately, I could not figure out how to make it be integrated with the board.

When I converted to a png file, the outline unfortunately did not have the outline as expected. It seems like kicad lacks features to convert dwg files or other file formats to lines within the program after importing.

I ended up tracing the outline again in kicad, but got this pretty interesting 3d view. If I have time, I will try making a container.