What should we do if the DS18B20 temperature probe fails?

The DS18B20 temperature probe is a sensor that senses temperature and converts it into a usable output signal. The temperature sensor is the core part of the temperature measuring instrument, and there are many varieties.

What is the pin definition of DS18B20 temperature probe?

What should we do if the DS18B20 temperature probe fails?

How to reduce the failure of DS18B20 temperature probe?

What is the pin definition of DS18B20 temperature probe?

(1) DQ is the digital signal input/output terminal;

(2) GND is the power ground;

(3) VDD is the input terminal of the external power supply (grounded in the parasitic power connection mode).

What should we do if the DS18B20 temperature probe fails?

1. Fault description:

According to on-site feedback and simulation tests, the fault conditions are as follows:

The board is repeatedly hot-swapped, and the temperature reading becomes 85C. However, the normal reading can be restored by repeated plugging and unplugging or power-on again.

2. Failure analysis:

The temperature sensor DS18B20 temperature probe in the test mode will set the value of the temperature register to 85C. At this time, if you directly read the temperature of the DS18B20 temperature probe, the result is 85C.

During the communication between the single-chip microcomputer and the DS18B20 temperature probe, if the communication is interrupted, for example, a higher-level interrupt occurs or other events

If there is a momentary power-off/power-on or ESD shock, the communication line of the DS18B20 temperature probe may hang up and enter the test mode. state at this time

state, it may not be able to communicate with the DS18B20 temperature probe, or it may always read 85C data or other random data.

How to reduce the failure of DS18B20 temperature probe?

In order to avoid the occurrence of the above situation, you can add a value before the subroutine that reads the temperature every time the microcontroller communicates with the DS18B20 temperature probe.

Add the following statement to ensure that the DS18B20 temperature probe exits from the bus hang or test mode, and completes the normal temperature conversion and data

Reported.

Reset / Presence Detect Bus initialization startup/detection process

0xCC / ignore ROM code (or 0x55 / check ROM code,)

0x64 / Internal reset command, set the temperature register to the initial value of 85C, and exit the test mode

Reset / Presence Detect Bus initialization startup/detection process

0xCC / ignore ROM code (or 0x55 / check ROM code,)

0x44 / temperature conversion command, perform temperature conversion and store the result in the temperature register

Please pay special attention that the internal reset command 64H must be executed immediately after the execution of the temperature conversion command 44H, because the 64H command

When resetting the DS18S20 and taking it out of test mode, the initial value set for the temperature register is 85C. in the implementation of the temperature

After the temperature conversion command 44H, the data of the temperature register is the actual temperature value.

As technology advances, DS18B20 temperature probe are increasingly used in our life. T Sensor Tech is known for high precision DS18B20 temperature probes. And you can connect them.