Analog sampling values transfer

MAX187 has an internal reference voltage, both 4 # pin (REF) is 4.096V, therefore, compact plc ,A / D conversion of the full range of 4.096V. The input signal is 0 ~ 5V, therefore, to add an op amp to 0 ~ 5V 0 ~ 4.096V after converted into MAX187. AT89C52 the P1.3 and chip select (CS) MAX187 connected, AT89C52 the P1.4 terminal and serial clock signal (SCLK) MAX187 is connected to the serial data output of AT89C52 the P1.5 and MAX187 (DOUT) connected. Value stored in the microcontroller memory analog sampling, plc analog input module and then by the microcontroller serial port to send to the PLC. A / D conversion of the C51 program is as follows,

#include
#include
sbit IC4_S = P1 ^ 4;
/ * AD input port settings * / sbit IC4_D = P1 ^ 5;
sbit IC4_C = P1 ^ 3;
void input (void)
{Unsigned char idata i;
unsigned int idata result = 0x0000;
IC4_C = 0;
/ * CS terminal is low * / for (i = 0; i <12; i ++)
{Result = result << 1;
  IC4_S = 0; / * clock terminal generates a clock pulse * /
IC4_S = 1;
if (IC4_D) result ++;
  / * Read from the serial data output of the A / D conversion data * /}
  IC4_C = 1; / * CS side is high * / pdat [1] = result;}

Analog input module expansion

Here take a 12 bit analog input as an example, analog signal to 0 ~ 5V standard voltage form into the signal input, plc digital input application 12 bit MAX187 conversion chip A/D realize analog conversion.

MAX187 is the 12 serial A/D, with a high conversion speed, the sampling frequency is 75kHz, input module plc and it is suitable for the process control of higher precision.

Taking into account the high frequency interference in the real industrial scene, the low-pass filter is used before the sampling signal MAX187.

PLC analog output module with low cost expansion

Programmable controller (hereinafter referred to as PLC) due to the high reliability, simple programming, strong versatility, small size, compact structure, installation, plc analog output module maintenance is convenient wait for a characteristic, and in industrial control has been widely used. General PLC module for the following categories, switch quantity input module, switch module output, analog input module and analog output module.

In the industrial control especially process control in the field of analog acquisition and control needs to be more, more and need of PLC Analog input and output module, and analog input and output module is more expensive and increase the analog input and output module increases the cost and reduce the price of the entire system, limit the application of PLC. This paper presents a method of extended analog input output module,  high-speed counter modules communication based on trying to solve this problem.

The role of the PLC input and output module

PLC input module is used for receiving, the various parameters of production process. (start stop input) output module plc  ,input module plc

The PLC output module is used to send can be obtained after computing the controller programming information, programmable logic controller manufacturer  and implementing agencies through the outside to complete all kinds of industrial field control. (the output)

1, have good anti disturbance ability.
2, can meet the requirements of all kinds of industry scene signal

PLC IO module and the electrical circuit

The pace of work from the vibration signal control. The operation is used for digital or logic operation, under the command of the controller work. Register to participate in operations, input module plc and to store intermediate results of operations, it is under the command of the controller.

CPU speed and memory capacity of PLC is an important parameter, which determines the pace of work PLC, IO number and software capacity, limiting the size of control.

PLC and the electrical circuit is through the input and output interface, complete the part (I/O). The IO module plc  integrated circuit PLC, the input registers to reflect the state of the input signal, the output reflects the state of the output latch.

PLC IO Modules

In 2010 and 2011, after years of double-digit growth of the recession, I / O module market started to recover, especially programmable controller module plc. However, the recovery of a distributed control system (DCS) I / O bit slow marketI / O
Modules, most of which is used with the controller, is an important part of complex industrial automation systems. By adding more IO module plc, the scope and flexibility of the entire automated system can be improved. PLC, for example, can move towards their ability to control the field level to increase the remote I / O modules. There are many active in this market suppliers, including a full range of automation products and expert mainly provides cpu module suppliers

Input module plc

PLC input module is the A / D converter module, with four independent analog input channels, output module plc signal for each channel can be 1 ~ 5V voltage signal can also be 4 ~ 20mA current signal. plc digital input module can input signal into a binary digital signal corresponding to eight, i.e. the measurement accuracy or resolution is eight of said. Decimal representation, it is converted into a value ranging from 0 to 255, provided to the PLC for further processing.
On the side of the module, corresponding to each plc ethernet module channel has a jumper, the user can be selected by shorting or jumper pins measuring not less then access signal is 1 ~ 5V voltage signal, or 4 ~ 20mA current signal. Signal conversion module, the maximum time is 2ms, the signal converter is working in parallel with the CPU of the PLC, the PLC scan time is not occupied.