Finishing the Weather Station Prototype PCB

Finishing the Weather Station Prototype Board#

Today was mainly about finishing the build of the PCB for the weather station prototype, rearranging the workshop so I can reach tools and parts more easily, and picking up a small fire extinguisher from Lidl.

The fire extinguisher was something of an opportunistic purchase, but considering I work with electronics and heat, it was probably a sensible addition to the workshop. Not that I intend on building incendiary devices anytime soon, but better safe than sorry.

The second part of the board build involved fitting the through-hole components. This mainly consisted of header pins for jumpers, header pins for the exposed GPIOs, and the sockets for the OLED display and BME280 sensor boards.

Once everything was fitted, I went through another testing cycle: checking for shorts, checking for invalid connections, and confirming the valid ones. Everything checked out fine.

With that done, I powered the board up again, and the ESP32-C3-SuperMini came to life and ran the LED blink test program without issue. So far, so good.

One issue I ran into was with the 0.96-inch OLED displays I had ordered from AliExpress. They differed from the 1.3-inch OLED displays in terms of pin layout.

On the 0.96-inch display, pin 1 is GND and pin 2 is VDD. On the 1.3-inch display, pin 1 is VCC and pin 2 is GND. The remaining pins appear to be the same.

It is not a massive problem, and I could always use a small bodge board if I really wanted to support the 0.96-inch displays, but thankfully the 1.3-inch OLED displays should match the expected pinout just fine. They are also easier to read, so that is likely the better option anyway.

The second issue I encountered was related to the regulator.

When I plugged my computer directly into the ESP32-C3-SuperMini, I noticed the board’s power LED coming to life, which was unexpected. It was then that I realised the ESP32-C3-SuperMini was back-powering the 3.3V rail, and a small voltage was effectively feeding in reverse through the LDO.

That is not necessarily a major problem in this design, as I have protection diodes on the 5V inputs, so the voltage is not getting beyond the LDO input. Even so, it is something I need to look into more carefully with the AP2114D-3.3 datasheet in hand, particularly around reverse current characteristics and whether additional protection (such as a blocking diode or ideal diode arrangement) is required.

Overall though, the prototype board is now assembled, powered, and behaving as expected, which is a good place to be.

The next step will be to write some code for the board and see how it behaves in practice.

If you are working on custom carrier boards, sensor integration, or ESP32 prototypes and need an experienced engineering partner, let’s discuss your project at Protoworks (NI).