DS18B20 Temperature Sensor Symbol
Definition: The DS18B20 Temperature Sensor symbol represents Maxim Integrated's (now Analog Devices) DS18B20 digital programmable-resolution 1-Wire temperature sensor IC in electronic schematics and wiring diagrams, depicted as a three-terminal device block with pins GND (ground), VCC (power supply), and DQ (1-Wire data bus), capable of measuring temperatures from −55°C to +125°C with up to 12-bit resolution over a single-wire serial interface.
Also known as: DS18B20 sensor, 1-Wire temp sensor, OneWire temperature sensor, digital temperature sensor, waterproof temperature probe, TO-92 temperature sensor.
What the DS18B20 Temperature Sensor symbol means
The DS18B20 Temperature Sensor symbol in an electronic schematic indicates the use of a digital temperature measurement IC that communicates via the 1-Wire (OneWire) protocol—a proprietary single-conductor serial bus developed by Dallas Semiconductor (now Maxim/Analog Devices). The symbol identifies the three critical connections: GND for circuit ground, VCC for power supply (or left unconnected in parasite-power mode), and DQ as the single bidirectional data line carrying both data and (in parasite mode) operating power.
The DS18B20 is widely used in hobbyist, industrial, and embedded systems to measure liquid, air, or surface temperatures without requiring analogue-to-digital conversion circuitry in the host microcontroller, as the sensor performs the conversion internally and returns a calibrated digital value. Each sensor has a unique 64-bit ROM code allowing multiple sensors to share the same DQ data line.
How to identify the DS18B20 Temperature Sensor symbol
The DS18B20 Temperature Sensor symbol is typically drawn as a small rectangle or three-pin IC block labelled 'DS18B20' with three connection lines: GND at the left, VCC at the left (above GND), and DQ at the right. In TO-92 package references (the flat-faced plastic transistor package), the three pins are identified as GND (pin 1, left), DQ (pin 2, centre), and VCC (pin 3, right) when viewing the flat face. In circuit diagrams the symbol may also appear as a generic three-terminal sensor block with the chip part number annotated. Waterproof probe variants show the sensor in a stainless-steel tube symbol with the same three electrical terminals.
Function in a circuit
The DS18B20 measures temperature by using an internal temperature-to-frequency conversion circuit, then performing an on-chip analogue-to-digital conversion and storing the result in an internal scratchpad register. The host microcontroller initiates a conversion, waits 93.75 ms (9-bit) to 750 ms (12-bit) for the conversion to complete, then reads the result over the DQ 1-Wire bus as a 16-bit signed two's-complement value with 0.0625°C resolution at 12 bits. Each DS18B20 carries a factory-calibrated unique 64-bit address (ROM code) that allows multiple sensors on the same DQ wire to be addressed individually.
Standards: IEC vs ANSI
| IEC 60617 | The DS18B20 is a proprietary component; there is no specific IEC 60617 schematic symbol for it. In schematics it is represented using the general IC symbol (rectangle with pins) as per IEC 60617-13 conventions for integrated circuits, labelled with the part number DS18B20. |
|---|---|
| ANSI/IEEE 315 | ANSI Y32.2 / IEEE 315 defines the general IC block symbol used to represent the DS18B20 in North American schematics—a rectangle with labelled input/output pins. There is no ANSI-specific symbol for the DS18B20 itself. |
| Key difference | Both IEC and ANSI represent the DS18B20 as a generic three-terminal IC block with pin labels (GND, VCC, DQ). The symbol shape is identical in both standards; the part number annotation distinguishes it from other three-terminal devices. No difference in symbol convention applies. |
Terminals / pins
| Pin | Name |
|---|---|
| gnd | GND |
| vcc | VCC |
| dq | DQ |
Typical values
Temperature range: −55°C to +125°C. Accuracy: ±0.5°C from −10°C to +85°C. Resolution: user-programmable 9-bit (0.5°C), 10-bit (0.25°C), 11-bit (0.125°C), or 12-bit (0.0625°C). Conversion time: 93.75 ms (9-bit) to 750 ms (12-bit). Supply voltage (VCC mode): 3.0 V to 5.5 V DC. Parasite power: 3.0 V to 5.5 V via DQ line (no VCC required). Package: TO-92 3-pin; also stainless-steel waterproof probe.
Where the DS18B20 Temperature Sensor symbol is used
- Arduino and Raspberry Pi DIY temperature monitoring projects measuring room, outdoor, or liquid temperatures over a single data wire
- Aquarium and fish tank controllers monitoring water temperature with a waterproof DS18B20 probe submerged in the tank
- Home brewing and fermentation temperature control systems measuring wort/beer temperature in fermentation vessels
- Industrial temperature logging systems using multiple DS18B20 sensors on a single 1-Wire bus running to a PLC or data logger
- Solar water heater and heat-pump controllers measuring collector and storage tank temperatures for differential control
- Soil temperature monitoring in greenhouse and agriculture automation systems
- HVAC duct air temperature sensing in small commercial building automation systems using ESP8266 or ESP32 microcontrollers
Example
In an Arduino-based multi-zone temperature monitoring schematic, six DS18B20 Temperature Sensor symbols are drawn with all six DQ pins wired to a common data line (Arduino digital pin 2) through a single 4.7 kΩ pull-up resistor to 5 V; all VCC pins connect to the 5 V supply rail and all GND pins connect to circuit ground. The Arduino sketch uses the OneWire and DallasTemperature libraries to address each sensor by its unique 64-bit ROM code and read individual temperature values in sequence.
Key facts
- The DS18B20 has three pins: GND (ground, pin 1 of TO-92), DQ (1-Wire data, pin 2), and VCC (supply voltage, pin 3); the DQ pin is the single-wire interface for both data and (in parasite power mode) operating current.
- The DS18B20 communicates via the 1-Wire protocol (Dallas/Maxim OneWire): a single bidirectional data line that requires a 4.7 kΩ pull-up resistor to the supply voltage to maintain the high idle state and allow open-drain signalling.
- Each DS18B20 contains a factory-programmed unique 64-bit ROM code (serial number), enabling multiple sensors to share the same DQ data wire and be addressed individually by the host—up to 100+ sensors on a single bus in typical implementations.
- Temperature measurement resolution is user-programmable from 9-bit (0.5°C, 93.75 ms conversion) to 12-bit (0.0625°C, 750 ms conversion) by writing the configuration register via the 1-Wire interface.
- In parasite power mode the DS18B20 draws operating current from the DQ line (through the pull-up resistor) during the idle and conversion phases, eliminating the need for a separate VCC supply wire—particularly useful in two-wire cable installations.
- The DS18B20 operates over −55°C to +125°C and achieves ±0.5°C accuracy from −10°C to +85°C without any external calibration; the calibration data is stored in on-chip EEPROM.
- The waterproof stainless-steel probe version of the DS18B20 encases the TO-92 sensor in a sealed 6 mm × 30 mm steel tube with PVC-coated leads, making it suitable for liquid immersion temperature measurement without additional sealing.
Frequently asked questions
What does the DS18B20 symbol represent in a circuit diagram?
The DS18B20 symbol represents a three-terminal digital temperature sensor IC from Maxim/Analog Devices (DS18B20) that communicates via the 1-Wire serial protocol. In a circuit diagram it indicates a device that measures temperature digitally and returns a calibrated value to a host microcontroller over a single data wire (DQ), alongside GND and VCC connections.
What are the GND, VCC, and DQ pins on the DS18B20 symbol?
GND is the circuit ground connection (pin 1 in the TO-92 package). VCC is the positive supply voltage input (pin 3, 3.0–5.5 V DC); it can be left unconnected in parasite power mode. DQ is the 1-Wire bidirectional data line (pin 2) through which all communication and timing occur; it requires a 4.7 kΩ pull-up resistor to the supply voltage.
What temperature range does the DS18B20 measure?
The DS18B20 measures temperatures from −55°C to +125°C (−67°F to +257°F). Its accuracy is ±0.5°C in the range −10°C to +85°C. Resolution is user-programmable from 9-bit (0.5°C steps) to 12-bit (0.0625°C steps). Conversion time increases with resolution from 93.75 ms at 9-bit to 750 ms at 12-bit.
What is parasite power mode on the DS18B20?
In parasite power mode the DS18B20 draws its operating current from the DQ data line via a parasitic capacitor inside the chip, eliminating the need for a separate VCC supply wire. The host microcontroller's pull-up resistor charges the capacitor through the DQ line during idle periods. Parasite mode simplifies wiring to just two conductors (GND and DQ) but limits bus cable length and the number of sensors that can perform conversions simultaneously.
How many DS18B20 sensors can share one data wire?
Multiple DS18B20 sensors can share a single DQ data wire because each contains a unique factory-programmed 64-bit ROM address. The host microcontroller uses 1-Wire ROM commands (MATCH ROM, SKIP ROM, SEARCH ROM) to address individual sensors. In practice 10–50 sensors work reliably on a single bus; cable length and pull-up resistor value limit the practical maximum.
What pull-up resistor does the DS18B20 DQ pin require?
The DQ pin of the DS18B20 requires a 4.7 kΩ pull-up resistor connected between DQ and the supply voltage (3.3 V or 5 V). This resistor provides the high logic level for the open-drain 1-Wire bus during idle and receive states. For longer cable runs or many sensors, a lower resistance (2.2 kΩ–3.3 kΩ) may be needed to maintain signal integrity.
What is the difference between the TO-92 DS18B20 and the waterproof probe version?
The TO-92 DS18B20 is a bare three-lead plastic semiconductor package suitable for PCB mounting or prototyping in dry environments. The waterproof probe version encloses the same DS18B20 sensor inside a sealed stainless-steel tube (typically 6 mm diameter, 30–50 mm long) with three colour-coded PVC-insulated leads (red = VCC, black = GND, yellow/white = DQ), making it suitable for immersion in liquids, soil, or wet environments.
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