Waterproof 1/3-Wire DS18B20 Digital temperature sensor

arduino, raspberry pi-dallas-sonoff esp8266-one wire DS18B20 temp sensor module probe kit.

DS18B20 is a commonly used digital temperature sensor probe (arduino, raspberry pi, multiple esp8266 DS18B20). Its output is a digital signal, which has the characteristics of small size, low hardware overhead, strong anti-interference ability and high precision.
The DS18B20 digital temperature sensor is easy to wire and can be used in a variety of situations after being packaged. Such as pipe type, threaded type, magnet adsorption type, stainless steel package type, various models, including LTM8877, LTM8874 and so on.
Its appearance mainly changes depending on the application. The encapsulated DS18B20 can be used for cable temperature measurement, blast furnace water circulation temperature measurement, boiler temperature measurement, computer room temperature measurement, agricultural greenhouse temperature measurement, clean room temperature measurement, ammunition depot temperature measurement and other non-limit temperature occasions. Wear-resistant and impact-resistant, small in size, easy to use, with various packaging forms, it is suitable for digital temperature measurement and control of various small space equipment.

How the DS18B20 temperature sensor works
The reading and writing timing and temperature measurement principle of DS18B20 are the same as that of DS1820, except that the number of digits in the temperature value obtained differs due to different resolutions. And the delay time during temperature conversion is reduced from 2s to 750ms. The temperature measurement principle of DS18B20 is shown in Figure 3. The oscillation frequency of the low temperature coefficient crystal oscillator in the figure is very little affected by temperature, and is used to generate a fixed frequency pulse signal and send it to counter 1. The oscillation frequency of the high temperature coefficient crystal oscillator changes significantly with temperature changes, and the generated signal is used as the pulse input of counter 2. Counter 1 and the temperature register are preset at a base value corresponding to -55°C. Counter 1 counts down the pulse signal generated by the low temperature coefficient crystal oscillator. When the preset value of counter 1 decreases to 0, the value of the temperature register will be increased by 1, the preset value of counter 1 will be reloaded, and counter 1 will restart counting the pulse signals generated by the low temperature coefficient crystal oscillator. This cycle continues until counter 2 counts to 0, then stops accumulating the temperature register value. At this time, the value in the temperature register is the measured temperature. The slope accumulator is used to compensate and correct the nonlinearity in the temperature measurement process, and its output is used to correct the preset value of counter 1.

Technical performance of DS18B20 temperature sensor
1. Technical performance description:
①. Unique single-wire interface method. When DS18B20 is connected to the microprocessor, it only needs one port line to achieve two-way communication between the microprocessor and DS18B20.
②. Temperature measurement range -55℃～+125℃, inherent temperature measurement error (note, not resolution, it was wrong before) 1℃.
③. Support multi-point networking function, multiple DS18B20 can be connected in parallel on the only three lines. Only up to 8 can be connected in parallel to achieve multi-point temperature measurement. If there are too many, the power supply voltage will be too low, resulting in unstable signal transmission.
④. Working power supply: 3.0~5.5V/DC (data line parasitic power supply can be used)
⑤. No external components are required during use.
⑥. The measurement results are transmitted serially in the form of 9~12-digit digital quantities.
⑦, Stainless steel protection tube diameter Φ6
⑧ Suitable for temperature measurement of DN15~25, DN40~DN250 various medium industrial pipelines and narrow space equipment
⑨. Standard mounting thread M10X1, M12X1.5, G1/2” optional
⑩, PVC cable outlet directly or German ball junction box outlet, easy to connect with other electrical equipment.
DS18B20+ and Maxim Integrated information [1]
Manufactured by Maxim Integrated, DS18B20+ is a temperature sensor.

Wiring method of DS18B20 sensor
The DS18B20 component faces the flat side, with negative left and positive right. Once connected incorrectly, it will become hot immediately and may burn! At the same time, reverse connection is also the reason why the sensor always displays 85°C. In actual operation, if the positive and negative connections are reversed, the sensor will heat up immediately and the LCD screen will not be able to display the reading. After the positive and negative are connected, it shows 85℃. In addition, if a 51 microcontroller is used, the middle pin must be connected to a 4.7K-10K pull-up resistor. Otherwise, because the high level cannot be input/output normally, it will either display 85°C immediately after powering on, or the temperature will jump randomly between 85°C and the normal value after a few months of use.

DS18B20 sensor wiring harness features
The unique one-line interface requires only one port line for communication and multi-point capabilities, simplifying distributed temperature sensing applications. No external components required Data bus power available, voltage range 3.0 V to 5.5 V No backup power required Measured over temperature range -55°C to +125°C. The Fahrenheit equivalent is -67°F to 257°F. Accuracy ±0.5°C over temperature range -10°C to +85°C
The programmable resolution of the temperature sensor is 9~12 bits. Temperature conversion to 12-bit digital format maximum 750 ms, user-definable non-volatile temperature alarm settings. Applications include thermostatic controls, industrial systems, consumer electronics thermometers, or any heat-sensitive system. Description The DS18B20 digital thermometer provides 9 to 12 digit (programmable device temperature readings). Since the DS18B20 communicates via a serial port line, there is only one serial port line connection between the central microprocessor and the DS18B20. For reading, writing and temperature conversion, energy can be obtained from the data line itself and does not require an external power supply. Because each DS18B20 contains a unique serial number, multiple DS18B20s can exist on the same bus at the same time. This allows temperature sensors to be placed in many different places. It has many uses, including air conditioning environment control, sensing the temperature inside buildings or machines, and for process monitoring and control.

one wire DS18B20 sensor

raspberry pi DS18B20 temp sensor module

arduino DS18B20 sensor probe kit

DS18B20 uses a first-line communication interface. Because of the first-line communication interface, ROM settings must be completed first, otherwise the memory and control functions will not be available. Mainly first provide one of the following function commands: 1) Read ROM, 2) ROM match, 3) Search ROM, 4) Skip ROM, 5) Alarm check. These instructions operate on the 64-bit photolithography ROM serial number of a device, and can select a certain device among multiple devices hanging on a line. At the same time, the bus can also know how many and what kinds of devices are on the bus.
If the command successfully causes the DS18B20 to complete the temperature measurement, the data is stored in the memory of the DS18B20. A control function directs the DS18B20 to perform temperature measurement. The measurement results will be placed in the DS18B20 memory and can be read by issuing memory functions commanded to read the contents of the on-chip memory. The temperature alarm triggers TH and TL have one byte of EEPROM data. If the DS18B20 does not use alarm check instructions, these registers can be used for general user memory purposes. On-chip also contains configuration bytes ideal for solving temperature-to-digital conversions. Writing TH, TL instructions and configuration bytes is completed using a memory function instruction. Read the register through the buffer. All data is read and written starting from the lowest bit.

Components of DS18B20 sensor:
DS18B20 memory
The memory of DS18B20 includes cache RAM and electrically erasable RAM. The electrically erasable RAM also includes temperature triggers TH and TL, and a configuration register. The memory can completely determine the communication of the first line port. Numbers are initially written into the register using the write register command, and then the numbers can be confirmed using the read register command. When confirmed, the copy register command can be used to transfer these numbers to electrically erasable RAM. This process ensures the integrity of the numbers when the numbers in the registers are modified.
The scratchpad RAM is composed of 8 bytes of memory;. The ninth byte can be read using the read register command. This byte is used to verify the previous eight bytes.

64-bit photolithographic ROM for DS18B20:
The first 8 bits of the 64-bit photolithography ROM are the DS18B20’s own code, the next 48 bits are continuous digital codes, and the last 8 bits are the CRC check for the first 56 bits. The 64-bit photolithography ROM includes 5 ROM function commands: read ROM, match ROM, jump ROM, search ROM and alarm search.

DS18B20 external power supply connection:
DS18B20 can use the external power supply VDD or the internal parasitic power supply. When the VDD port is connected to a voltage of 3.0V-5.5V, an external power supply is used. Internal parasitic power is used when the VDD port is grounded. Whether it is an internal parasitic power supply or an external power supply, the I/O port line must be connected to a pull-up resistor of about 5KΩ.

Configuration register of DS18B20:
The configuration register configures different bits to determine temperature and digital conversion.
It can be known that R1 and R0 are the determining bits of temperature. Different combinations of R1 and R0 can be configured as 9-digit, 10-digit, 11-digit, or 12-digit temperature display. In this way, the conversion times corresponding to different temperature conversion positions can be known. The resolutions of the four configurations are 0.5°C, 0.25°C, 0.125°C and 0.0625°C respectively, and are configured as 12 bits when shipped from the factory.

Temperature reading of DS18B20:
The DS18B20 is configured as 12-bit when shipped from the factory. When reading the temperature, a total of 16 bits are read, and the first 5 bits are sign bits. When the first five bits are 1, the temperature read is a negative number. When the first five bits are 0, the temperature read is a positive number. The reading method when the temperature is positive is to convert the hexadecimal number into decimal. When the temperature is negative, the reading method is: invert the hexadecimal system, add 1, and then convert it to decimal system. Example: 0550H = +85 degrees, FC90H = -55 degrees.