It’s almost time to plant my pepper plants. (I usually target 10-12 weeks before plant-out which is late May to early June around here.) I like to monitor and control temperature and humidity under the seedling dome. My existing sensor was giving me some problems, so I decided to wire up a replacement.

This is a pretty simple setup using an ESP32 Devkit running Tasmota talking I2C to a BME280 and a BH1750 Lux sensor. I connect this to my home automation system running on Home Assistant. I solder the Devkit to a perfboard so I can add an XH connector. This allows me to keep the ESP32 itself out of the high humidity of the seedling dome with a short wire. The wiring is dead simple. Power, Ground, SDA, SCL. Sometimes I’ll work through the microscope to make sure the solder has flowed well and I don’t have any bridging between pads. (It sure looks messy when you’re up that close.)

I install Tasmota on the ESP32 and configure it to talk to my Mosquitto server. Home Assistant is already listening in on that MQTT server, so adding a display and some automations is simple. I have a heat mat controlled by a “smart plug” running Tasmota. (The UI claims it is “on” but it’s currently unplugged.) I should be ready to plant when the day comes!


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