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Analog Devices (Maxim) · Integrated circuit

DS18B20 Temperature Sensor

1-Wire digital thermometer. Dozens share a single microcontroller pin, each with its own 64-bit address. Flat face toward you, pins down.

Cheat sheet (SVG)
Logic level
3.0-5.5 V
Package
TO-92 / SOIC-8 / waterproof probe

1.Pinout diagram

Highlight a signalhover to preview, click to keep

TO-92, flat face toward you

DS18B20

Pin detail

Hover a pin for its mappings and gotchas. Click to keep it here.

Logic level
3.0-5.5 V
Package
TO-92 / SOIC-8 / waterproof probe

Fig. 1. DS18B20 Temperature Sensor, TO-92. Hover or tap a signal to light up every pin that carries it.

2.Watch out

  • DQ needs a 4.7k pull-up to VDD. One resistor for the whole bus, not one per sensor.
  • Every device has a unique 64-bit ROM address, so many sensors share one pin. Read the addresses once and hard-code them, or the order can change between boots.
  • Parasitic power ties VDD to GND and runs the sensor off DQ. It works, but conversion needs a hard pull-up on the data line during those 750 ms, which usually means a MOSFET. Running a third wire is nearly always easier.
  • A 12-bit conversion takes up to 750 ms. Asking for the value immediately after requesting it returns the previous reading, which looks like lag that tracks your loop rate.
  • Counterfeits are everywhere, especially in cheap waterproof probes. They typically fail at the extremes, ignore the resolution setting, or report in 0.5 degree steps. If readings look quantized, that is why.
  • Rated minus 55 to 125 C, but the waterproof probes are only good to about 100 C because of the cable and the potting.
  • On a Raspberry Pi the w1-gpio overlay expects GPIO4, pin 7 on the header.

3.1-Wire bus

What has to go around the chip before it will run.

VCCGNDDS18B20GND (1) to GNDVDD (3) to VCC4.7 kOhm between DQ (2) and VDD (3)4.7 kOhmGND 1DQ 2VDD 3
Fig. 2. 1-Wire bus, drawn from Table 1. Crossing wires are not connected.
Table 1. External parts, and why each one is there.
PartBetween
4.7 kOhmDQ (2) to VDD (3)

In parasitic power mode VDD ties to GND and the sensor runs off DQ, but conversion then needs a hard pull-up on the data line, usually a MOSFET. A third wire is easier.

4.Full pin reference

Every pin, alias and mapping. This is the table that prints.

Table 2. Pin assignments.

Complete pin reference for DS18B20 Temperature Sensor
PinNameFunctions

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Primary sources

Found a wrong pin? The whole board is one file, data/boards/ds18b20.json.

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