CN207557152U - A kind of novel pH value intelligent measure circuit - Google Patents

Abstract

The utility model designs a novel portable pH value intelligent measuring circuit, which includes a minimum system composed of a controller, a measuring electrode, a display module and a wireless module. The controller adopts HC16L series single-chip microcomputer; the measurement part adopts PH sensor, including temperature compensation electrodes; the display and wireless transmission modules adopt PCD8544 and ESP8266 respectively. The intelligent measuring instrument can detect and display the pH value of the measured liquid, and can transmit the data wirelessly. The intelligent measuring instrument has high reliability, strong anti-interference ability and low power consumption.

Description

A New Type of PH Value Intelligent Measuring Circuit

technical field

The utility model design belongs to a novel measurement circuit applied to the pH value detection of a solution, and is mainly a high-precision, low power consumption, and high-efficiency pH detection circuit.

Background technique

Each substance has a different PH value, and the PH value has a great influence on the substance itself, so the study of PH is of great significance to our life and scientific research, and whether the PH value of the substance can be accurately measured is the key appear more important. With the continuous development of science and technology, traditional pH measurement can no longer meet the needs of research in various fields. In practical applications, we urgently need to obtain the pH value in real time. For example, in the fields of clinical monitoring in hospitals, chemical process control in factories, monitoring and protection of human working and living environments, and those dangerous places where sampling is difficult, obtaining chemical information is also very difficult. Therefore, it is very important for the research and application of existing pH detection instruments and the development and application of new pH detection instruments. The PH value detection circuit of this design selects the main control chip, display screen and IC devices with a lower price under the condition of sufficient precision, thus effectively controlling the cost and realizing a more accurate, faster and more real-time detection of the PH value. The detection has very important practical significance.

Contents of the invention

The purpose of this utility model is to improve the deficiencies of the existing technology and cost, to design a PH value detection circuit suitable for actual production and applied to portable instruments, to improve the flexibility and accuracy of detection, and to have high performance and high reliability. PH value detection circuit.

This design system is mainly divided into two parts: the first part is the minimum system composed of HC16LC16K6TALQFP64 MCU chip, which completes the system control and data processing functions through the connection of I/O interface and peripheral circuit. The second part is the peripheral analog circuit (PH value amplification circuit and temperature compensation circuit), which processes the voltage value of the PH electrode through the IC chip circuit and amplifies and transmits it to the main control chip to complete the measurement and display of data.

Control and display system advantages of the design

Processor selection: The selection of the processor did not use the MCU of foreign brands, but the HC16LC16K6TALQFP64MCU of the domestic chip HC16L series with cheaper price and better performance. The FP64 chip adopts the 16-bit CPU platform of 80251. The processing capability of the 80C51 is 40 times faster, and has a CPU clock of up to 16MHZ, with three low-power modes, the current can reach as low as 0.9 microamps, the sleep mode is 40 microamps, and the working mode is 260 microamps; Wake up from consumption mode to work mode, the response time is less than 3 microseconds, which is one-half of the MSP430 series, and has a very fast response speed; its working temperature is -40 ~ 85 ° C, can adapt to harsh working scenarios, single power supply The power supply is 1.8 ~ 3.8V (suitable for portable devices). Generally speaking, it is an MCU with high integration, high anti-interference, high reliability and ultra-low power consumption. Make the cost of the instrument lower if the requirements are met.

Improvement of precision and security: It has 64-bit hardware DES encryption and decryption coprocessor and 16-bit hardware CRC check circuit module, and unique 8-byte ID number, which has high reliability and security.

Faster wake-up time: Every MCU available for portable instruments has a power management system, HC16LC16K6TALQFP64MCU has three low-power modes, one sleep mode and one work mode, wake up from low power mode to work mode , The response time is less than 3us, which makes the switching speed faster and consumes less energy.

Choice of display chip: The display uses an LCD screen instead of an LED screen, which is cheaper and more power-saving. This design uses the PCD8544LCD screen used in the Nokia 5110 mobile phone, which can display four lines of characters, which fully meets the requirements of the instrument. Requirements, and the module is small in size, powered by low voltage, and has a power-down mode, which saves more power.

Selection of the displayed LCD screen: The selected LCD screen model is PCD8544, which is an LCD screen used in the Nokia 5110 mobile phone. The reasons for selection are as follows:

High cost performance. PCD8544 can display 15 Chinese characters and 30 characters, and the price is at least half cheaper than other LCD screens such as 12864 and 1602, or even more.

The interface is simple. Only four I/O lines can be driven.

high speed. It is 20 times of LCD12864 and 40 times of LCD1602.

The PCD8544 has a working voltage of 3.3V, an operating current of less than 200uA, and a power-down mode, which is very suitable for battery-powered portable mobile devices.

Improvements and advantages of the designed PH detection circuit

For the PH detection circuit, the original preamplifier circuit is selected from the dual op-amp operational amplifier LM4562. Its biggest advantages are low cost, high precision, low noise and low input bias current. LM4562 is a high-fidelity dual operational amplifier IC with ultra-small distortion, only 0.00003% total harmonic distortion and noise (THD+N), in other words, the distortion of LM4562 operational amplifier is almost negligible. And the LM4562 chip also has the advantages of extremely low distortion rate, low noise, high conversion rate, wide operating voltage range and large output current, and its performance is unprecedented. Therefore, it is suitable for the application of portable detection equipment.

This design uses 18b20 as the solution temperature sensor. 18b20 is a commonly used temperature sensor, which has the characteristics of small size, low price, strong anti-interference ability and high precision. And the data measured by 18b20 can be directly transmitted to FP64 MCU, the hardware circuit design is simple, and the error is small. The measurement data of 18b20 can be directly transmitted to the I/O port of FP64 MCU to realize the data transmission.

Description of drawings

Figure 1 is a schematic diagram of the system configuration

Figure 2 is a schematic diagram of the link between the minimum system and the display screen and wireless module

Figure 3 is a schematic diagram of the pH value detection and temperature compensation circuit

Detailed ways

As shown in Figure 1, the whole system of the novel PH detection circuit comprises: PH sensor module (for measuring the PH electrode value and its temperature value of spirulina culture liquid); PH sensor interface circuit module (completes the amplification of PH electrode value) ;Temperature sensor interface circuit module (used to measure and read the temperature value for temperature compensation); HC16LC16K6TALQFP64 main control chip constitutes the smallest system module (realize the function of data reading, processing and output), LCD display (use It is used to display the measured pH value and the temperature value of the currently tested solution).

The minimum system and the circuit connection shown are shown in Figure 2. The DVSS pin of the FP64 MCU is connected to VCC (3.3V) to supply power for itself, and the resistor R3 (4.7K) and C6 capacitor (0.1uF) are connected to the RSTB pin to form the minimum system. The reset circuit is used for the reset operation of FP64 MCU. AVSS1 pin and AVSS2 pin are grounded, capacitor C4 (4.7uF) is connected to VDD_CORE (LDO capacitor interface), C5 (0.1uF) is connected to AVCC2 to form an analog power interface, DVCC The three pins of digital ground pin, AVSS1 and AVSS2 analog ground pins are grounded, capacitors C8 (12pF) and C9 (12pF) and X1 (32.768KHZ crystal oscillator) constitute the external crystal oscillator of FP64 MCU, which is used as an external clock.

The circuit connection between FP64 MCU and PCD8544: the VDD pin of PCD8544 is connected to the DVCC (digital power supply) pin of FP64 MCU to supply power for LCD, and the SCLK pin (serial clock input terminal) of PCD8544 is connected to the SPICLK pin of FP64 MCU ( SPI clock (slave input, master output) is the LCD input clock signal, and the SDIN pin (serial data input pin) is connected to the SPIMOSI pin (SPI master data output, slave data input) of the FP64 MCU as the LCD input data. The pin (data/command) is connected to the SPIMISO pin (SPI master data input, slave data output) of FP64 MCU for LCD mode selection, select command/address or input data, pin and The pin is connected to the ordinary I/O (input and output pin) of LP64 MCU, the GND pin of PCD8544 is directly grounded, and the VOUT pin is grounded after connecting the capacitor.

The circuit connection between FP64 MCU and ESP8266: the VCC pin of ESP8266 is connected to the VCC power supply (3V3), the CH_PD pin is the enable pin, which is connected to the high level and is also connected to VCC. The GND pin is grounded. The RST pin of ESP8266 is a reset pin, which is used as an external hardware reset. It is connected to the common I/O interface of FP64 MCU, and FP64 MCU is used to control the reset operation of ESP8266. The UTXD pin (serial port transmission) of ESP8266 is connected to the RXD1 pin (serial port reception) of FP64 MCU, and the URXD (serial port reception) pin of ESP8266 is connected to the TXD1 pin (serial port transmission) of FP64 MCU for data transmission and reception.

Connection of the PH detection circuit: As shown in Figure 3, the V+ pin of U1 is connected to VCC, and the V- pin is grounded to provide power for it. After R3 and C1 are connected in parallel, one end is connected to ground and the negative pole of Zener diode D1, and the other end is connected to resistor R2 and the positive input port of U1. One end of R1 is connected to VCC, and the other end is connected to the positive pole of Zener diode D1 and one end of R2. Connection, the negative input port of U1 is connected to the output port of LM4562 and the negative electrode of the PH electrode. Like U1, the V+ pin of U2 is connected to VCC, and the V- pin is grounded to provide power for it. One end of R4 is grounded, and the other end is connected to the negative input port of U2; one end of R5 is connected to the negative input port of U2, and the other end is connected to the output port of U2; the positive pole of the PH electrode is connected to the positive input port of U2; the output port of U2 is connected to P3 of the MCU. 0 interface. The 18b20 temperature signal is directly connected to the P3.1 pin of the MCU.

Claims (6)

1. a kind of novel pH value intelligent measure circuit, it is characterised in that：Including MCU circuits, peripheral analog circuit, temperature sensing Device circuit, display circuit, ESP8266 wireless modules,

The MCU circuits are the functions of connecting to complete circuit control and data processing by I/O mouthfuls and peripheral circuit；

The periphery analog circuit is used to handle the voltage value of PH electrodes；

The temperature sensor is used to detect the temperature of testee；

The display circuit is used to show the pH value and temperature of object being measured；

The ESP8266 wireless modules are connected with MCU circuits.

2. a kind of novel pH value intelligent measure circuit according to claim 1, it is characterised in that：The MCU circuits packet Include main control chip HC16LC16K6TALQFP64, capacitance C2, capacitance C3, capacitance C4, capacitance C5, capacitance C6, capacitance C7, capacitance C8, resistance R7 and crystal oscillator X1.

3. a kind of novel pH value intelligent measure circuit according to claim 1, it is characterised in that：The PH sensor electricity Road includes resistance R1, resistance R2, resistance R3, resistance R4, resistance R5, capacitance C1, Zener diode D1, operational amplifier U1 and fortune Amplifier U2 is calculated, the operational amplifier U1 positive input terminals are connected with resistance R2, resistance R3 with one end of capacitance C1, the fortune The negative input end for calculating amplifier U1 is connected with output terminal, the other end of the resistance R3 and capacitance C1 and the one of Zener diode D1 End is connected and is grounded, and the resistance R2 is connected with the other end of Zener diode D1 with one end of resistance R1, the resistance R1's Another termination VCC, the negative input end of the operational amplifier U2 are connected with one end of resistance R4, resistance R5, the resistance R5's The other end is connected with output terminal, the other end ground connection of the resistance R4.

4. a kind of novel pH value intelligent measure circuit according to claim 1, it is characterised in that：The temperature sensor Circuit includes 18B20 chips and resistance R6, the VCC pin of the 18B20 chips and termination a VCC, the 18B20 of resistance R6 The DQ pins of chip are connected with the other end of resistance R6, the GND pin ground connection of the 18B20 chips.

5. a kind of novel pH value intelligent measure circuit according to claim 1, it is characterised in that：The display circuit packet PCD8544 chips and capacitance C7 are included, GND with the VOUT pins of the PCD8544 chips are connected with one end of capacitance C7, the electricity Hold the other end ground connection of C7.

6. a kind of novel pH value intelligent measure circuit according to claim 1, it is characterised in that：The ESP8266 without Wire module includes ESP8266 chips.