Clearing out a drawer at work I found a bag of Grove modules: temperature and humidity (DHT11 version), a light sensor, a loudness sensor and a Grove relay. No Base Shield, and the board I want to use is an ESP32 DevKit anyway, which a shield wouldn’t fit. The plan is a little monitor for our parcel sorting room: temperature, light and noise to Hermetry every minute, plus switching a fan.
Can I wire Grove modules directly with jumpers? The 4-pin connectors have yellow, white, red, black and I’m not sure what each is, or whether 3.3 V is enough for them.
Oh I have the same kit! Never knew what white was for
Wouldn’t it be easier to just buy the shield?
The shield is for Uno-shaped boards, the ESP32 DevKit doesn’t plug in.
Grove is just a connector convention, wire it with Grove-to-female-jumper cables (or cut one cable in half). Did a classroom kit like this on ESP32s.
Digital and analog modules:
yellow SIG (the main signal: digital or analog out)
white NC or second signal (unused on most single modules)
red VCC
black GNDI2C modules use yellow = SCL, white = SDA.
Voltage is the part to check per module. The light sensor (v1.2) and loudness sensor are analog and run fine at 3.3 V, their output stays below 3.3 V, so straight into ESP32 ADC1 pins (GPIO32-39; ADC2 doesn’t work while Wi-Fi is on). The DHT11 module works at 3.3 V too, with a short cable. The Grove relay coil is 5 V: power it from the 5 V pin (VIN on the DevKit with USB), its input is happy with a 3.3 V signal.
Don’t feed any module 5 V if its output goes into an ESP32 pin, the ESP32 isn’t 5 V tolerant.
The loudness sensor gives an envelope, not audio. Sample it every 50 ms and send the max and average for the minute, e.g. {"temperature": 21, "light": 1830, "noise_avg": 312, "noise_max": 744}, so a forklift going past shows up as a peak.
Stick to ADC1 even for testing, I lost an hour to ADC2 reading 4095 with Wi-Fi on.
The light sensor is pretty nonlinear btw, fine for „lights on or off“ but don’t treat it as lux.
If you want lux later, a BH1750 on I2C is cheap and the same Grove wiring works.
All wired with cut Grove cables, everything at 3.3 V except the relay on VIN. Light and loudness on GPIO34 and 35. Noise max is already the most fun chart on the board: you can see every pallet jack pass. Ciaran, yes, my first try was on GPIO4, ADC2, stuck at 4095.
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