Switching to ESP32 For Next Exercise

After deciding to move data processing off of the microcontroller, it would make sense to repeat my exercise with an even cheaper microcontroller. But there aren’t a lot of WiFi-capable microcontrollers cheaper than an ESP8266. So I looked at the associated decision to communicate via MQTT instead, because removing requirement for an InfluxDB client library meant opening up potential for other development platforms.

I thought it’d be interesting to step up to ESP8266’s big brother, the ESP32. I could still develop with the Arduino platform with an ESP32 but for the sake of practice I’m switching to Espressif’s ESP-IDF platform. There isn’t an InfluxDB client library for ESP-IDF, but it does have a MQTT library.

ESP32 has more than one ADC channel, and they are more flexible than the single channel on board the ESP8266. However, that is not a motivate at the moment as I don’t have an immediate use for that advantage. I thought it might be interesting to measure current as well as voltage. Unfortunately given how noisy my amateur circuits have proven to be, I doubt I could build a circuit that can pick up the tiny voltage drop across a shunt resistor. Best to delegate that to a dedicated module designed by people who know what they are doing.

One reason I wanted to use an ESP32 is actually the development board. My Wemos D1 Mini clone board used a voltage regulator I could not identify, so I powered it with a separate MP1584EN buck converter module. In contrast, the ESP32 board I have on hand has a regulator clearly marked as an AMS1117. The datasheet for AMS1117 indicated a maximum input voltage of 15V. Since I’m powering my voltage monitor with a lead-acid battery array that has a maximum voltage of 14.4V, in theory I could connect it directly to the voltage input pin on this module.

In practice, connecting ~13V to this dev board gave me an audible pop, a visible spark, and a little cloud of smoke. Uh-oh. I disconnected power and took a closer look. The regulator now has a small crack in its case, surrounded by shiny plastic that had briefly turned liquid and re-solidified. I guess this particular regulator is not genuine AMS1117. It probably works fine converting 5V to 3.3V, but it definitely did not handle a maximum of 15V like real AMS1117 chips are expected to do.

Fortunately, ESP32 development boards are cheap, counterfeit regulators and all. So I chalked this up to lesson learned and pulled another board out of my stockpile. This time voltage regulation is handled by an external MP1584EN buck converter. I still want to play with an ESP32 for its digital output pins.

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