DS18B20 (waterproof probe)
Also known as: DS18B20 · Dallas temperature probe · 18B20 · Temperature & humidity
The probe-on-a-wire: waterproof, chainable (a dozen sensors on one GPIO), and happy in a pool, freezer, pipe or compost heap where no PCB sensor survives.
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At a glance
⚑ flag an error| Measures | temperature |
|---|---|
| Accuracy | ±0.5 °C (genuine); clones frequently miss this spec |
| Interface | 1-Wire (many probes share one GPIO; parasite-power option (genuine only)) |
| Supply | 3.0–5.5 V |
| Battery-viable | Yes (deep-sleep friendly) |
| ESPHome | Native ESPHome component — dallas_temp |
| Typical price | $1-2 (street, varies) |
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Clone check
HIGH clone risk. The best-documented fake epidemic in hobby electronics: a 1000-probe study found essentially ALL eBay/AliExpress waterproof probes counterfeit. Tells: parasite power doesn't work, offsets beyond ±0.5 °C, ROM not matching 28-xx-xx-xx-xx-00-00-xx. How to check what you received →
Good for
Gotchas to know
- Assume AliExpress probes are clones: they mostly work, but skip parasite power, keep runs short, and sanity-check readings against a known thermometer.
- Needs a 4.7 kΩ pull-up on the data line.
- Genuine chips only from real distributors (Mouser/DigiKey) — the probe housings are never genuine.
Wiring it up
Simple wiring: one data GPIO (with a 4.7 kΩ pull-up — and multiple probes can share it) on any ESP32 dev board.