Design of Wireless Temperature Measurement and Control Circuit Based on LabVIEW

Test - lowercase jpg

Kaixin micro test

Test probe P100-M3

Wireless Crystal 3.2*2.5mm 3225 25M (25.000MHZ) 12PF 10PPM 20PPM 30PPM

The temperature measurement and control system is mainly composed of a computer, a single chip microcomputer, a temperature measuring circuit, a temperature control circuit and a wireless communication circuit. The TMPll2 temperature sensor performs temperature acquisition, and after transmitting the temperature digital quantity to the P89LV51RD2, the on-site temperature display is performed through the digital tube LED circuit. At the same time, P89LV51RD2 sends the temperature data to the remote computer through the wireless communication module SZ05. The LabVIEW control platform running on the PC displays the temperature in real time, and performs data processing, temperature alarm and data storage. In addition, the control platform samples the input signal, uses the PID controller in LabVIEW to perform PID control, and sends the control amount to the single-chip microcomputer through the wireless module, and the output control amount of the single-chip microcomputer realizes temperature control.

Temperature control circuit

The temperature control circuit is shown in Figure 2. It is mainly composed of an NPN transistor Q1, a TLP521-1 type photocoupler U1, and a high power NMOS transistor Q2. The upper computer program control system compares the detected temperature value with the system set value, performs calculation according to the PID control algorithm, and outputs a PWM signal with adjustable duty ratio from the P1.2 port of the single chip, and controls the photoelectric coupling after being driven by the transistor Q1. The on/off of the U1 is controlled, and then the on-off time of the NMOS transistor Q2 (IRF840A) is controlled, thereby controlling the heating time of the heating object-the high-power resistor R to reach the set temperature value. For the convenience of experiment, R is a high-power wirewound resistor with rated power of 10W and rated resistance of 10Ω. It is powered by +12V DC power supply. Since the current flowing through the heating resistor R is large, the +12V DC power supply for R must be separated from the +12V DC power supply that supplies power to other analog devices.

The temperature measurement and control system uses a low-power single-chip microcomputer system as the acquisition module, which replaces the expensive data acquisition board, has low cost, and is temperature-processed and controlled by the software platform developed by LabVIEW. Compared with the traditional instrument, the temperature measurement and control system has a friendly interface. Easy to operate and highly scalable. The system can be embedded in the virtual instrument experiment platform as part of the teaching experiment system for students to learn LabVIEW programming and communication between virtual instruments and microcontrollers. In addition, multiple nodes can be networked to form a distributed wireless network to achieve multi-point temperature measurement and control, which has a good application prospect.