PLC switch, analog conversion

PLC switch quantity, analog switch, must first clear three meanings: device signal layer, PLC software application layer, the PLC internal processing. Equipment layer: the switch is on and off signals, analog voltage signal is linear or linear current signal

PLC controller software application layer: switch quantity is 0, 1, switch node in a binary form in PLC internal register, analog quantities ( Such as 255, 32767, 65535) In hexadecimal form is stored in the PLC user register. Internal processing layer: all out of register to adopt binary arithmetic. Switch analog conversion in the PLC software application layer (as long as the use of related instructions Such as mitsubishi K1M0) Switch binary conversion into hexadecimal in PLC users can register.

switch and analog conversion is generally been keeping and digital, switch quantity, for example, there are interference, to eliminate the interference, software can eliminate interference, such as a switch state reading every few milliseconds, both read only think the switch is closed, otherwise considered interference, interference can also use the hardware to eliminate interference, of course, if Schmitt trigger, etc.

for analog, also after quantification, such as 0809 AD conversion, the conversion method, here also couldn't say for sure, you can query the chip data, 0809 chip control conversion pin, can make pin, convert address control such as pin, using 8051 single chip microcomputer to control the transformation, of course, there are advanced microcontroller, MSP430, AVR microcontroller, better conversion chips, such as DSP STM32 series chips, is a specialized analog-to-digital conversion chip. Conversion principle is based on the precision of the conversion chip division transfer quantity, such as, digits for eight conversion chips, suppose convert analog for 5 v voltage, then can be divided into 256 (the 5 v Because of 8 bit chip is only) Forever, so that it can be concluded that the digital quantity, and vice versa. Common voltage and current signals of analog signals, and the input signal to control equipment, such as frequency converter speed control, pneumatic proportional valve, etc. , the output signal and all kinds of sensors and other output devices. They need to refer to the AD and DA conversion relationship between modules and equipment range to determine.

DA module which the relationship between digital and analog signal voltage below:

module end 4000 range corresponding 10 v voltage signal, the digital quantity according to the relationship. In equipment side inverter frequency and the relationship between the analog is: 50. 00 hz corresponds to 10 v voltage signal input, so in the relationship between frequency and digital conversion in PLC programming is the digital quantity = 1. 25 hz or 1 hz = 0. 8 digital quantity, join us to control the inverter 30. 00 hz, will be to write 2400 digital quantity DA module.

AD module its analog voltage and the relationship between the digital quantity below:

at the module end 4000 digits corresponding to a 10 v analog quantity, according to the relationship. On devices such as the position sensor and the relationship between the distance with the analog voltage signal is: 200 mm range corresponding to 10 v analog output, there in the PLC program to get the accurate location, position and the relationship between the digital quantity is 1 mm = 20 digital digital quantity = 0 or 1. 5 mm, to join our tested the 2000 digital quantity, after conversion to know position is 100 mm. As for the switch and analog conversion between relations, and how it should be said that analog control switch quantity, such as motor speed above a certain value will turn off the motor, how many degrees temperature is greater than will stop heating or less than how much to heating, this time we went through the AD module to monitor the data, compare in the PLC, output the corresponding switch action according to the comparison results.

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