【正文】 n the software to program must pay attention. When uses analog modules and so on temperature, various factories also have some stipulations, please refer to the correlation technique four, PLC works design , when carries on the work design with PLC, its difficulty controls the PLC single plane is much bigger than, first is elected with the quite familiar type, has the thorough understanding to its elementary instruction and the function mand, and the instruction carries out the speed and the user program storage capacity should also the inquire closely. Otherwise cannot adapt the realtime request, creates the system collapse. Moreover to the correspondence connection, the munication protocol, the data transfer speed and so on must consider. must seek the work design and the software support and the detailed technical data finally to the PLC factory, as for selects several workstations, decides according to the system size. the five, softwares establish Before piling the software, should first be familiar with the PLC product instruction booklet which selects, after treating familiar, programs again. If uses the graph programmer or the software package programming, then may program directly, if with the handhold programmer programming, should draw the trapezoidal chart first, then the programming, may reduce like this makes a mistake, the speed is also quick, after forming pletes, revolves spatially first, after treating each movement normally, then on the equipment debugs. The pulse quantity39。 When the system is big, must expand. The different pany39。s metal structure connection, es under the bad influence. 7. PLC external drive electric circuit cannot lead the load directly regarding the PLC output in the situation, must in exterior use the driving circuit, may use the solid state relay or the thyristor electric circuit actuates, simultaneously should use the protection circuit and the surge absorbing other PLC input output wiring also has certain request, please refer to various panies39。s input current is bigger than PLC the biggest input current or has leaks the electric current, will contain errors the movement, reduces the sensitivity. Therefore should be suitable the weakcurrent input and to leaks the electric current to take the protective measure, and selects the input to supply to leak input PLC. When the two types sensor (electrooptical switch, noncontact switch) have the LED limit switch, the input leakage is inoperable for lack has the wrong input or the lamp is bright, the countermeasure reduces the input impedance for the connection bleeder, the resistance number by Figure 1 equation development: when the transistor or the bidirectional siliconcontrolled rectifier output, if receives big surge current on the equipment, must consider the protection transistor and the siliconcontrolled rectifier. The transistor and the siliconcontrolled rectifier may undergo the nominal current 10 time of surge currents, if surpasses, may according to Figure 2, chart 3 one reduce it: 5. Processes to the perceptual load When input, output termination perceptual load, must in the load both sides parallel impact blanker or the diode, diode39。s overload or short circuit will affect PLC the movement). 3. exterior DC24V power source If the input circuit has the DC24V power supply proximity switch, the electrooptical switch and so on, but on the PLC DC24V power source capacity is insufficient time, must provide the DC24V power source from exterior。s design 1. power source return route The PLC power supply is generally AC85240V (also has DC24V), adapts the power source scope to be wide, but for the antijamming, should install the power source to purify the part (for example power source filter, 1:1 insulating transformer and so on) on DC24V power source39。s selecting and purchasing: the PLC programming may adopt three ways: First, with the general handhold programmer, it can only use in the sentence table sentence programming which the factory stipulated. Center way easy scene debugging, and the volume small cost is low, but its efficiency low adaptation aircraft type type are few, pared with is suitable is small in the system capacity, in amount used few systems. Second, the graph programmer programming, this way uses the graphic mode programming, facilitates intuitively, generally the electrical personnel shortterm may apply freely, but the programmer price is high. Third, programs with IBM and the patible personal puter +PLC software package, this way is the efficiency highest one way, is also the most monly used one way, but the majority of software package price is expensive. 7. selects the big pany39。s steady operation is very important. 3. The storage capacity and the instruction carry out the speed are the PLC shaping important targets, generally the reserves is bigger, the speed quicker PLC price to be higher, although overseas various factories product more or less the same, but also has certain difference. 4. “COM choice, different PLC product, it COM a quantity is dissimilar, some COM belt 8 output spots, some belt 4 output spots, also has the belt 1 or 2 output spot. When the load type are many, and the electric current is big time, uses one COM a belt 12 output product, when the load type minority quantity are many, uses one COM a belt 48 output product. 5. Because each Manufacturer39。s Simens, South Korea39。s selecting and purchasing: in the present market39。s make and break, the product counting, the temperature, the pressure, the current capacity hypothesis and the control and so on, in the industry scene39。s CPU instructions with stepbystep process to store the address of the program counter, running in the process, each step in the implementation of the automatic counter plus 1, stepbystep process f