3.3 V Compatibility

Choose breakouts that run at 3.3 V or have onboard regulators and level shifting. A 5 V output connected straight to an ESP32 GPIO can damage the pin over time.

Digital Over Analog

The ESP32’s ADC is noisy and slightly non-linear. Digital sensors (I2C, UART, 1-Wire) give calibrated readings without fiddly ADC tuning, so prefer them where you can.

I2C Addresses

Many sensors can share one I2C bus as long as their addresses differ. Two identical sensors may need an address jumper, or the ESP32’s second I2C port.

Accuracy vs Price

The DHT22 is cheap and fine for trends. For a thermostat or mold monitoring, an SHT31 or BME280 is more accurate and more stable over time.

Power Draw

For battery nodes with deep sleep, pick sensors with low standby current (BME280, SHT31, AM312). Fan-based particulate sensors and mmWave radar draw much more and suit mains-powered devices.

When humidity accuracy matters, for mold prevention, a humidor, a greenhouse or an incubator, Sensirion’s SHT31 is a step up from the DHT22. This breakout (about 4.7 stars from 36 ratings) specifies ±2% RH across the full 0–100% range and measures temperature from −40 to 125 °C over I2C, at 2.4–5.5 V. It has a built-in heater to clear condensation in very humid environments, and it’s supported by ESPHome’s sht3xd platform and common Arduino libraries. Sensirion’s newer SHT40 is similar and even smaller if you see a well-reviewed listing.

The BME680 is the BME280’s bigger sibling: it adds a heated metal-oxide VOC gas sensor to temperature, humidity and pressure, so one breakout can flag cooking smells, cleaning products or a stuffy room. This ACEIRMC board (about 4.2 stars from 45 ratings) works over I2C or SPI. The raw gas reading is a resistance that changes with VOCs; to turn it into an IAQ index, use Bosch’s BSEC library, which ESPHome supports with its bme680_bsec platform. Note that its “eCO2” output is an estimate from VOCs, not real CO2, so pair it with an SCD41 if CO2 is what you need. HiLetgo’s version (B0CDWXZNY7) is also well rated.

The DHT22 (also sold as the AM2302) is the classic first sensor for ESP32 tutorials, and this HiLetgo 2-pack is the most-reviewed climate sensor in this guide (about 4.4 stars from 709 ratings). It uses a single data wire, the module includes the pull-up resistor, and libraries like DHT sensor library or ESPHome’s dht platform read it in a few lines. The trade-offs are speed and precision: it can only be read every two seconds, it’s less accurate and stable than an SHT31 or BME280, and its timing-sensitive protocol occasionally returns failed reads. It’s perfect for learning and for rooms where a degree either way doesn’t matter.

For aquariums, pools, hot-water tanks, fermenters, freezers and soil temperature, the DS18B20 in a stainless-steel waterproof probe is the standard choice. This HiLetgo 5-pack (about 4.4 stars from 378 ratings) covers −55 to 125 °C on the 1-Wire bus, which means you can connect several probes to a single ESP32 GPIO and read each by its unique address. Add one 4.7 kΩ pull-up resistor between the data and 3.3 V lines, since bare probes don’t include it. Use the OneWire and DallasTemperature libraries or ESPHome’s dallas_temp platform. Only 5 were left in stock when we checked.

Smoke from wildfires, cooking or a wood stove shows up as fine particulates, which CO2 and VOC sensors can’t see. Plantower’s PMS5003 uses a small fan and a laser to count particles and reports PM1.0, PM2.5 and PM10 concentrations over UART. It’s the sensor behind many community air-quality monitors, and this listing (about 4.3 stars from 72 ratings) includes the connector cable. Power it from 5 V (the fan needs it) while its serial lines use 3.3 V logic that suits the ESP32. ESPHome supports it via the pmsx003 platform. Because the fan draws continuous current and wears over time, use the SET pin to sleep it between readings.

A PIR sensor only sees movement, so lights switch off while you’re sitting still reading. The LD2410C is a 24 GHz FMCW radar that detects people who are sitting or lying still by picking up breathing-level motion, which makes it the go-to sensor for reliable room occupancy in Home Assistant. This 3-pack (about 4.4 stars from 57 ratings) gives you a sensor for several rooms. It has a simple digital presence output plus UART for distance and per-zone sensitivity, which ESPHome exposes through its ld2410 component, and the “C” version can also be tuned over Bluetooth with HiLink’s app. Power it from 5 V; its signal pins use 3.3 V logic.

For battery-powered motion sensors, hallway night-lights and wake-on-motion cameras, the tiny AM312 PIR is a better match for the ESP32 than the larger HC-SR501. It runs from 2.7–12 V, so it works directly from the ESP32’s 3.3 V rail, and its digital output can wake an ESP32 from deep sleep as an external wake-up source. This HiLetgo 3-pack has about 4.2 stars from 250 ratings. It has a fixed short hold time and no adjustment pots, which keeps it simple. Only 6 were in stock when we checked.

ST’s VL53L0X measures distance by timing a pulse of invisible 940 nm laser light, so it’s far more precise and has a much narrower beam than ultrasonic sensors, and it works on soft surfaces that absorb sound. It’s ideal for robot obstacle detection, gesture-triggered switches, mailbox and parcel sensors, and short-range object counting, typically up to about 1–2 m depending on the surface and lighting. This 5-pack (about 4.4 stars from 33 ratings) uses I2C. All units share the same default address, so use the XSHUT pins to assign new addresses at boot when using several. ESPHome supports it with vl53l0x.

The HC-SR04 is the familiar two-eyed ultrasonic sensor, and it’s still the cheapest way to measure distances of several metres, such as water-tank levels, parking sensors and robot bumpers. This WWZMDiB 2-pack has about 4.6 stars from 228 ratings. The important ESP32 caveat: the classic HC-SR04 is a 5 V module and its ECHO pin outputs 5 V, so put a simple voltage divider (for example 1 kΩ and 2 kΩ) between ECHO and the ESP32 GPIO. The TRIG input is happy with a 3.3 V pulse. ESPHome supports it with the ultrasonic platform. For wet environments like tanks, look for a waterproof JSN-SR04T instead.

The MPU6050 on a GY-521 breakout is the most-reviewed sensor in this guide (about 4.6 stars from 802 ratings for this HiLetgo 3-pack). It combines a 3-axis accelerometer and 3-axis gyroscope over I2C, which is everything you need for tilt sensing, step and vibration detection, self-balancing robots, gesture controllers and drone experiments. Its onboard motion processor can fuse the readings into orientation, and libraries like Adafruit MPU6050 and I2Cdevlib make it straightforward. TDK has discontinued the original chip, so modules on the market vary; it remains fine for hobby use, while newer IMUs like the ICM-42688 suit precision work.

An LDR (photoresistor) on the ADC only gives a rough “bright or dark” value. The BH1750 reports calibrated ambient light in lux over I2C, so automations like “turn on the lights below 50 lux” or “close the blinds above 20,000 lux” behave consistently. This HiLetgo 3-pack has about 4.5 stars from 81 ratings, with 16 in stock. Two units can share one I2C bus by setting the ADDR pin, and ESPHome supports it with the bh1750 platform. It’s also handy for plant-growth monitoring and display auto-brightness.

The INA219 measures DC bus voltage, current and power on the high side of a circuit and reports it over I2C, which makes it the easy way to monitor a solar panel, a 12 V battery, a USB device or your own ESP32’s deep-sleep current. This HiLetgo 2-pack has about 4.2 stars from 84 ratings. The common breakout uses a 0.1 Ω shunt for roughly ±3.2 A, and the chip handles bus voltages up to 26 V DC. Up to four can share one bus with address jumpers, and ESPHome supports it with the ina219 platform. For mains (AC) power, use a dedicated isolated energy-monitoring module instead.

Cheap two-prong resistive soil probes corrode within weeks. A capacitive soil moisture sensor measures moisture through a coated PCB with no exposed metal, so it lasts far longer in damp soil. This Songhe listing (about 4.3 stars from 227 ratings) is a popular choice for ESP32 plant monitors and automatic watering systems. It gives an analog output, so connect it to an ADC1 pin and calibrate by recording the reading in dry air and in a glass of water, then map between them. Seal the top electronics with heat-shrink or nail polish for outdoor use, and power it only when reading to save battery and reduce drift. Quality varies between capacitive sensor batches, so test each one.

Weather station?

BME280 + BH1750, with a DS18B20 for ground temperature.

Indoor air quality monitor?

SCD41 for CO2 + PMS5003 for particulates, or a BME680 for VOCs.

Lights that know you’re there?

LD2410C mmWave for presence, AM312 for battery motion.

Plant monitor?

Capacitive soil sensor + BH1750 + SHT31.

Tank level or parking sensor?

HC-SR04 for metres, VL53L0X for precise short range.

Solar or battery monitor?

The INA219 for DC voltage, current and power.

Can I connect 5 V sensors to an ESP32?

You can power them from the 5 V (VIN) pin, but their output signals must not exceed 3.3 V at the ESP32’s GPIO. Use a resistor voltage divider for slow digital signals like the HC-SR04’s ECHO, or a bidirectional level shifter for I2C on 5 V-only modules. Most modern I2C breakouts run happily at 3.3 V, so no shifting is needed.

Why does my temperature sensor read too high?

The ESP32 and its voltage regulator warm up, especially with Wi-Fi on, and a sensor mounted on or near the board picks up that heat. Put the sensor on a short cable away from the board, read it less often, and use deep sleep between readings where you can. An offset correction in software can handle any remaining bias.

How many I2C sensors can I connect to one ESP32?

Many, as long as each has a different address and the total bus capacitance stays reasonable. The ESP32 has two I2C controllers, so two identical sensors with fixed addresses can go on separate buses. For more identical sensors, use an I2C multiplexer such as the TCA9548A.

What’s the difference between eCO2 and real CO2?

Sensors like the BME680, CCS811 and SGP30 estimate an “equivalent CO2” from VOC readings, which can be far off in real rooms. NDIR and photoacoustic sensors like the SCD41 measure CO2 molecules directly. If you’re making ventilation decisions, use a true CO2 sensor.

Should I buy a 37-in-1 sensor kit instead?

Assortment kits are fun for exploring, and HiLetgo’s 37-sensor kit (B01N5910XS) is a popular one, but most modules in them are basic analog or digital boards built for 5 V Arduinos. For real projects, the individual digital sensors in this guide are more accurate and work better at 3.3 V.