Development and design of the hottest intelligent

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Development and design of an intelligent shrinkage machine

Abstract: a development and design based on Intelligent shrinkage machine is applied to the shrinkage test of various fabrics. Therefore, it is urgent to develop a new generation of shrinkage machine with excellent performance, appropriate price, reliable quality and high intelligence

key words: instrument amplifier 485 communication AD conversion

with the development of society, people's living standards are constantly improving, and people's pursuit of quality of life is also improving. Clothing, food, housing and transportation must take the lead. Various popular fabrics and fashions are constantly introduced in the market. A few laboratories adopt semiconductor refrigeration tanks, and new fabrics come out every day. In this way, higher requirements are put forward for the testing of these fabrics. In the testing of various technical properties of fabrics, the determination of shrinkage is a very important item, which is a very key technical index in the testing of fabrics. Therefore, it is urgent to develop a new generation shrinkage machine with excellent performance, appropriate price, reliable quality and high intelligence

shrinkage machine, as its name suggests, is a machine for measuring fabric shrinkage. From the current perspective, our first generation products have huge volume, rough appearance, old and unsophisticated circuits, poor reliability, and main components are self-produced, such as motors, which are often damaged. This time, through market research and analysis, we found that the appearance, mechanical structure, motor, solenoid valve, etc. of Siemens and drum washing machines are ahead of their peers, and are similar to our requirements. Therefore, we put forward the idea of using Siemens shell to reform the shrinkage machine. Through dissection, we abandoned all the mechanical program-controlled parts and used the new control system designed by ourselves. The program operates in accordance with relevant international and domestic standards. Practice has proved that our program is successful

this paper mainly introduces the data acquisition process of the sensor, and explains in detail the usage of its device and the whole working process of the circuit

1. system structure (Figure 1)

1.1. Keyboard display circuit, such as key query, temperature display, water level display, etc., should be completed by it. Therefore, the keys and panel display cannot occupy too much time of the main CPU. Therefore, we use a very mature 8279 chip to manage the keyboard and display, and achieved good results

1.2. Data acquisition of the sensor, a single piece of AT89C52 is used as the acquisition of temperature data and pressure data. After data acquisition, it is transmitted to the main CPU board through RS485 signal

1.3. The driving part of peripherals is completed by solid-state relay. Solid state relay has no mechanical contact, photoelectric isolation, simple drive, no spark, and more importantly, it has zero crossing trigger. The switches of electrical equipment are at the zero point of input AC, reducing interference. Therefore, in this machine, these devices all use solid-state relays (among them, the motor speed regulation part adopts DCSSR). In the whole process, the control of the motor is the key. After thoroughly dissecting the structure and circuit of the motor, it is found that the control circuit is controlled by a special circuit of tda1085c produced by Motorola Company, and the whole control part is simple and reliable. In view of this, we decided to control the motor by indirectly controlling this board. In this way, the cost is saved and the reliability is improved

1.4. The main CPU board is the core of the whole system. It completes the collection and processing of sensor data, then sends it to the display, and drives the peripheral devices according to the program requirements. Among them, when the main CPU and keyboard display circuit interface, it is forbidden for the main CPU data bus to directly carry out IO operations with peripherals (connected with each other through flat cables), which ensures that the genx engine adopts the stability of composite fan blades and full composite fan casing at the same time, and the correct judgment of pressing keys. Half duplex RS485 interface is used for serial communication between master and slave CPUs, which has strong anti-interference ability. At the same time, since the slave CPU has integrated data processing such as temperature and water level, it is packaged and sent to the main CPU, which reduces the burden on the main CPU. Because the whole system needs to expand many port lines, the logic integration chip isplsi2064 is used in the main circuit to expand the completion of i/o ports and other logic functions

2. data acquisition circuit of the sensor (Figure 2)

2.1. water level detection

in the technical requirements, there is a requirement to display the water level in real time. According to the previous method (float method), there can only be a few water level points, but cannot be measured continuously, and the water level is always out of control and overflows. Therefore, we choose SMI micro pressure sensor smi5551 of the United States, using the original leather tube, Indirectly measure the water level by measuring the change of air pressure caused by the change of water level. The principle is shown in Figure 3:

Figure 3

2.2. Signal amplification and adjustment

since this sensor is a micro pressure sensor and its output is millivolt level, it is amplified with an instrument amplifier

the instrument amplifier adopts ina128 from TI company of the United States, which is a low-voltage general-purpose instrument amplifier. Its characteristics are as follows:

· low offset voltage: 50 μ Vmax;

· low drift: 0.5 μ V/℃max;

· low input drift: 5na max

· high common mode rejection ratio: 120dB min

· wide passband: 200kHz (g=100)

· input overvoltage protection: ± 40V

· wide power supply voltage range: ± 2.25 ~ ± 18V

· low quiescent current: 700 μ A;

· 8-pin plastic dip and SO-8 package

due to its excellent characteristics, small size and convenient gain setting from 1 to 10000 with an external resistance, ina128 can be widely used in many fields such as signal acquisition and amplification, medical instruments and multi-channel systems. It can work at a power supply voltage as low as ± 2.25V and the static working current is very small. It is an ideal device for portable and other battery powered systems

a.ina128 application precautions

gain setting

Figure 2 shows the basic connection of ina128. With an independent external resistor RG, the magnification can be obtained as: g=1 + 50K Ω/rg

where 50K Ω is the sum of the feedback resistances of the two amplifiers inside ina128. Both of them have been laser corrected and have high accuracy and small temperature coefficient. The device performance given in the manual has included their influence. The accuracy and temperature stability of the external resistance directly affect the gain, especially when the gain is large (g ≥ 100), the resistance of the wiring and socket will also bring additional errors to the gain. In other words, the RG value in the formula should be the sum of the external resistance and the stray resistance such as the connection

noise interference

the internal noise of ina128 is very small. When G ≥ 100, the low-frequency noise from 0.1 to 10Hz is only about 0.2 μ Vp-p, which is much smaller than the latest low-noise chopper amplifier. In order to reduce the influence of external interference and power supply noise, a decoupling capacitor should be added close to the power pin

in addition, the output voltage takes ref terminal as the reference point. Generally, ref should be well grounded to ensure a good common mode rejection ratio of the amplifier. Increasing the series resistance of 8 Ω at pin ref will reduce the common mode rejection ratio by 80dB (g=1)

in this example, the ref is terminated with a 1.2V reference to match the output range of the micro pressure sensor smi5551 and the output range of the subsequent AD conversion

offset compensation

ina128 is laser corrected. Therefore, the offset and temperature drift are very small, and in most cases, there is no need to adjust. If necessary, the circuit can be externally compensated. The voltage follower isolates the zeroing circuit from the instrument amplifier, maintains the low impedance of pin ref, and ensures a good common mode rejection ratio of the amplifier. The current source can be replaced by an integrated circuit (such as ref200) or a resistor. Of course, when using resistors, the unstable power supply will affect the output

the input impedance of the charge discharge path at the input end

ina128 is very high, which is prone to charge accumulation, making the input voltage exceed the allowable range of common mode voltage, causing the input amplifier to be saturated. However, there are several ways to provide a discharge path for charges. The secondary center tap of the transformer is used as the discharge path. For low impedance signal sources such as thermocouples, connect leakage resistance at one end. For high impedance signal sources, such as microphones and underwater detectors, symmetrical circuits should be used to reduce input misalignment and improve common mode rejection ratio

common mode input signal range

if the common mode voltage in the input signal is too large, the input amplifier will be saturated. At critical saturation, the output voltage of VO is vo=vcm - vo/2. The linear input range of ina128 is about 1.7V above the negative power supply to 1.4V below the positive power supply. For the determined power supply voltage, the larger the output voltage Vo, the smaller the allowable common mode signal. If the common mode input Ao is too large, it will be saturated

low voltage operation

ina128 is characterized by a wide range of applicable power supply voltage. When the power supply voltage changes from ± 2.25V to ± 18V, most parameters can still maintain good performance. Ina128 can be used under low voltage and can be used as an ideal device for portable or battery power supply systems. However, when using low voltage, special attention should be paid to ensure that the input signal is within the limited range, and the common mode input voltage should not be too large

input protection

ina128 input protection circuit can provide ± 40V overvoltage protection, that is, adding - 40V voltage to one input terminal and + 40V voltage to the other input terminal will not cause damage. Under normal signal conditions, the overvoltage protection circuit presents low series impedance; When the input voltage is too large, the protection circuit can limit the input current to a safe range of 1.5 ~ 5mA. Ina128 also has overvoltage protection against possible electrostatic charges at the input without power supply

3. AD conversion circuit (Figure 2)

ina128 amplifies the millivolt level signal to 1.2v---5v, and then converts it from ad to digital quantity

ad converter adopts high-speed 8-bit analog-to-digital converter tlc0820ac of American TI company

tlc0820ac is an advanced LINCMOS 8-bit analog-to-digital converter. It is composed of two 4-bit flash converters, a 4-bit analog-to-digital converter, an addition (error) amplifier, control logic and a result locking circuit. The improved flash technology enables low-power integrated circuits to μ S completes 8-bit conversion. The on-chip sample and hold circuit has a 100ns sampling window, allowing these devices to operate at up to 100mV/μ S ramp rate converts continuous analog signals without external sampling devices. TTL compatible 3-state output driver and two working modes allow interface with different microprocessors. Its features are as follows:

· advanced LINCMOS silicon gate technology

· 8-bit resolution

· differential reference input

· parallel microprocessor interface

· conversion and access time within the temperature range, reading method: 2.5 μ S max

· no external clock or oscillator is required

· on chip sampling and holding

· a single 5-volt power supply

is converted into a digital signal with tlc0820ac, and then the water level is calculated by referring to the quantization curve, and the average value of multiple water levels is taken to eliminate the change of water level caused by the rotation of the barrel. The drift elimination and zero adjustment of the amplifier are automatically completed by software

4. communication interface circuit (Figure 4)

Figure 4

the master and slave CPUs use half duplex RS485 interface for serial communication, which has strong anti-interference ability. At the same time, since the slave CPU has integrated data processing such as temperature and water level, it is packaged and sent to the main CPU, which reduces the burden on the main CPU

rs485 serial communication interface selection

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