CN214426840U - Weak photoelectric spectrum signal detection system based on STM32 singlechip - Google Patents

Abstract

The utility model discloses a weak photoelectric spectrum signal detecting system based on STM32 singlechip. Belongs to the field of single chip microcomputer detection; the device comprises a power supply module, a photosensitive sensing module, an instrument amplification module, an MCU detection module and a display module. The utility model realizes the integrated design of self power supply and extremely weak current detection; in a front-end analog system, a TIA circuit is added into a preamplifier to reduce noise, a power supply is simplified, a digital processing part utilizes an MCU to carry out wavelet transformation algorithm, the design of the whole photoelectric current detection system is simplified, weak photoelectric current can still be detected with high sensitivity under the condition of meeting portability and self power supply, the detection sensitivity is 100nA, and the performance requirements of general photoelectric detection are completely met.

Description

Weak photoelectric spectrum signal detection system based on STM32 singlechip

Technical Field

The utility model relates to a singlechip detects technique, concretely relates to weak photoelectric spectrum signal detecting system based on STM32 singlechip.

Background

The photocurrent detection is a technology for detecting weak current generated by the photoelectric effect, is an important detection method, has wide application, and is applied to the scientific research fields of electrochemistry, astronomy, space science and the like and industrial detection scenes of water quality detection, atmospheric detection and the like. In photocurrent detection, weak current is generally referred to as 10^-6Current of the order of a and below. The weak photocurrent signal has the characteristics of low signal-to-noise ratio and weak signal, so the weak signal detection technology is widely applied to photocurrent detection. Aiming at the requirements, it is necessary to research and manufacture a weak photoelectric spectrum signal detection system based on an STM32 single chip microcomputer.

With the development of detection devices and the increase of detection requirements, more and more application scenes are available for signal acquisition and test by using a photoelectric spectrum testing instrument. However, since the signal collected by the photoelectric TFT is weak, there are many requirements and problems to be met and solved in the application: firstly, a general weak photocurrent detection instrument is expensive, large in size, not suitable for an industrial field detection environment, and cannot be produced in batch and embedded into an industrial detection system; secondly, for a very weak photocurrent detection system based on a lock-in amplifier, the modulation frequency of a current signal can drift in some detection scenes, so that the lock-in amplifier generates a frequency lock-in error, the detection result is affected, and the application of the detection system is limited.

SUMMERY OF THE UTILITY MODEL

In order to solve the problems, the utility model provides a weak photoelectric spectrum signal detection system based on an STM32 single chip microcomputer; the utility model discloses divide into front end analog part and digital processing part with the system, carry out the integrated design to photocurrent detection and modulation drive light source in front end analog part, add low pass filter according to detecting the frequency in the testing section to utilize power isolation measure to avoid extra power supply. The digital processing part utilizes the MCU to realize a wavelet transformation algorithm, thereby reducing the complexity of the system; in practical tests, the detection sensitivity of the system can reach 100nA, and the system completely meets the requirement of general photocurrent detection.

The technical scheme of the utility model is that: the utility model discloses a weak photoelectric spectrum signal detection system based on STM32 singlechip, including power module, power module pass through the wire line and connect respectively on photosensitive sensing module, appearance are with amplifying module, MCU detection module and display module;

the STM32 singlechip-based weak photoelectric spectral signal detection system improves the performance of an ultrahigh-impedance circuit by using an electrometer-grade operational amplifier ADA 4530-1; thereby making the photosensitive sensing module suitable for circuit impedance of 100M omega to 10T omega;

the power module adopts a 3.3V lithium battery; the photosensitive sensing module adopts an ADA4530-1 chip; the instrument amplification module adopts an AD623 instrument amplification chip; the MCU detection module adopts a stm32f7 high-performance development board as a main control unit, and the AD sampling module adopts an on-chip AD conversion module of a singlechip; the display module adopts a TFTLCD series 4.3-inch liquid crystal display screen.

The utility model has the advantages that: the utility model realizes the integrated design of self power supply and extremely weak current detection; in a front-end analog system, a TIA circuit is added into a preamplifier to reduce noise, a power supply is simplified, a digital processing part utilizes an MCU to carry out wavelet transformation algorithm, the design of the whole photoelectric current detection system is simplified, weak photoelectric current can still be detected with high sensitivity under the condition of meeting portability and self power supply, the detection sensitivity is 100nA, and the performance requirements of general photoelectric detection are completely met.

Drawings

FIG. 1 is a flow chart of the structure of the present invention;

fig. 2 is a schematic diagram of a boosting part of the power module according to the present invention;

FIG. 3 is a schematic diagram of a power supply module according to the present invention;

FIG. 4 is a schematic diagram of the photosensitive sensor module according to the present invention;

FIG. 5 is a schematic diagram of the magnifying module for center instrument of the present invention;

FIG. 6 is a schematic diagram of the AD623 amplifying chip in the amplifying module for instruments of the present invention;

in the figure, 1 is a power supply module, 2 is a photosensitive sensing module, 3 is an instrument amplification module, 4 is an MCU detection module, and 5 is a display module.

Detailed Description

In order to more clearly illustrate the technical solution of the present invention, the following detailed description is made with reference to the accompanying drawings:

as depicted in fig. 1; a weak photoelectric spectrum signal detection system based on an STM32 single chip microcomputer comprises a power supply module 1, wherein the power supply module 1 is respectively connected to a photosensitive sensing module 2, an instrument amplification module 3, an MCU detection module 4 and a display module 5 through wired lines; wherein different modules can be changed and adjusted according to the actual situation to obtain the detection image with the optimal effect.

The weak photoelectric spectral signal detection system based on the STM32 single chip microcomputer improves the performance of an ultrahigh-impedance circuit to the greatest extent by using an electrometer-grade operational amplifier ADA 4530-1; the performance advantage thus makes the photosensitive sensing module suitable for circuit impedance of 100M omega to 10T omega above, and adopts eight-channel input to satisfy the multichannel sensitization input demand.

The power module 1 (direct current power module) adopts a 3.3V lithium battery; a power module 1 which uses a 3.3V lithium battery for self power supply is built; in view of the continuous and stable supply of 5V by the battery, the PS7516 power chip is used to boost the 3.3V lithium battery (as shown in fig. 2) in view of the portable requirement, and the PS7516 ensures that the 5V power supply voltage can be stably supplied; on the other hand, the inverse characteristic of the ICL7660 power supply chip is used for providing a voltage of-5V for power supply (as shown in FIG. 3), so that continuous and stable dual power supply of the whole system is ensured, and as the MCU detection module 4 needs to work under 1.7V-3.6V, the voltage division operation needs to be carried out on the power supply voltage.

As shown in FIG. 4, the photosensitive sensing module 2 adoptsUsing ADA4530-1 chip; due to the fact that the TIA transimpedance amplification circuit is used, the input bias current is as low as 20fA level, the offset voltage is 50uV low, and after the standard TIA transimpedance amplification circuit is built, preliminary amplification can be provided to output a measurement voltage signal; the TIA circuit simulates the current output sensor as a belt shunt resistor (R)_i) Current source (I)_i) (ii) a The current from Vc-terminal is connected to the inverting input pin of ADA4530-1 and the feedback resistor (R)_F) (ii) a Driving the Vc + terminal and the non-inverting input of the amplifier to a suitable reference voltage; the negative feedback of the circuit can inhibit the voltage change on the A end; this suppression is achieved by forcing all current to flow through the feedback resistor; if all error sources are ignored, the output of the circuit is as follows:

V_out＝I_i*R_F

the instrument amplification module 3 adopts an AD623 instrument amplification chip; the instrument amplification module 3 (shown in fig. 5) built by the three operational amplifiers uses an output differential amplifier to convert differential voltage into single-ended voltage and also inhibits any common-mode signal on the output end of the input amplifier; since the amplifier's swing can reach either end of the supply voltage and its common mode range can be extended below the negative supply voltage; thus further improving the swing range of the AD 623; as the gain of the instrumentation amplification block 3 increases, the bandwidth of the AD623 will decrease because a1 and a2 are voltage feedback operational amplifiers (as shown in fig. 6); however, due to the excellent performance of the AD623, the amplifier module 3 still has sufficient bandwidth to be suitable for many applications at a higher gain; the voltage measuring circuit has the advantages that the input bias current is as low as 20fA, the offset voltage is 50uV, and after a standard TIA trans-impedance amplifying circuit is built, preliminary amplification can be provided to output a measuring voltage signal.

For the instrument amplification module 3, the input signal is applied to the PNP transistor as a voltage buffer and a DC level shifter (as shown in fig. 6); the use of a 50k Ω resistor in the feedback path of each amplifier (a1 and a2) with precision adjusted to within 0.1% ensures accurate gain setting; if all error sources are ignored, the differential output is:

in the formula, R_GIn units of k Ω.

The MCU detection module 4 adopts an STM32F7 high-performance development board as a main control unit, wherein an AD sampling module adopts an AD conversion module in a singlechip; sampling and holding the eight input photoelectric signals, converting the sampling values into digital values, and finally inputting codes into the MCU for judgment; the MCU detection module 4 using STM32F7 as a main control unit uses a wavelet transform algorithm for the AD converted waveform; the wavelet transform uses a series of wavelets with different scales to decompose the original function, and the transformed original function obtains coefficients under the wavelets with different scales; different wavelets are decomposed through translation and scale transformation, the translation is used for obtaining the time characteristic of the primitive function, and the scale transformation is used for obtaining the frequency characteristic of the primitive function; therefore, the photoelectric data can obtain waveforms and data under various scales.

The display module 5 adopts a TFTLCD series 4.3-inch liquid crystal display screen.

The utility model discloses the working process concrete description is as follows:

1. the photosensitive sensing module 2 and the instrument amplification module 3 form a peripheral detection circuit, and the shell is made of dark opaque acrylic materials, so that the interference of metal materials on signal transmission can be avoided on the basis of ensuring that the light transmission is not influenced by the surrounding environment;

2. the power module 1 and the MCU detection module 4 form a middle basic circuit, in order to ensure that the power supply of each circuit module 1 is normal, a thicker signal wire is needed to transmit current, and the power supply is positioned between the inside and the outside, so that the power consumption is reduced, the whole working life is prolonged, the required space is reduced, and the portability is facilitated; in order to avoid the attenuation of the measurement signal as much as possible, the MCU detection module 4 is arranged behind the instrument amplification circuit 3, so that the signal propagation distance is reduced;

3. the AD module adopts an STM32 singlechip on-chip AD conversion module, when the voltage of the photosensitive sensing module 2 is measured by the measuring circuit, a signal is input into the AD sampling module for AD conversion, and then the signal is read into the singlechip for processing;

4. after a period of signals are collected, the STM32 single chip microcomputer operates wavelet transform detection, performs local analysis on spatial frequency, gradually performs multi-scale refinement on the signals through telescopic translation operation, and finally outputs the signals to the 4.3-inch TFTLCD screen display module 5 through a serial port.

Claims (1)

1. A weak photoelectric spectrum signal detection system based on an STM32 single chip microcomputer is characterized by comprising a power supply module, wherein the power supply module is respectively connected to a photosensitive sensing module, an instrument amplification module, an MCU detection module and a display module through wired lines;

the STM32 singlechip-based weak photoelectric spectral signal detection system improves the performance of an ultrahigh-impedance circuit by using an electrometer-grade operational amplifier ADA 4530-1; thereby making the photosensitive sensing module suitable for circuit impedance of 100M omega to 10T omega;

the power module adopts a 3.3V lithium battery; the photosensitive sensing module adopts an ADA4530-1 chip; the instrument amplification module adopts an AD623 instrument amplification chip; the MCU detection module adopts a stm32f7 high-performance development board as a main control unit, and the AD sampling module adopts an on-chip AD conversion module of a singlechip; the display module adopts a TFTLCD series 4.3-inch liquid crystal display screen.

Images