Step7 programming quick start experience sharing - Database & Sql Blog Articles

Single chip microcomputer STM32L151CCU6

Mobile phone crystal 3.2*2.5mm 3225 26M (26.000MHZ) 7.5PF 10PPM 20PPM 30PPM

SMD aluminum electrolytic capacitor

Brand AVX TPSE226M035R0125 Low impedance tantalum capacitor AVX 22

L0504-Murata muRata common mode inductor 90Ω 150mA

First of all, you should understand before you go to school, what is the complete part of STEP7, as shown below:



After understanding the task solution, create a project with STEP7, then do option 1 (assemble the hardware first, then program) or option 2 (program first, then assemble the hardware), and then download the program to the CPU for debugging.

Programming example

The following uses the 57-300plc to control the start and stop of the three-phase asynchronous motor as an example to introduce the use of STEP7 software. In this example, the function realized by the PLC is equivalent to the control circuit shown in Fig. 1. Externally, a start button SB1, a stop button SB2 and an output contactor KM are connected. The terminal wiring diagram of the PLC is shown in Fig. 2. Where FR is a thermal breaker, the FR acts when the motor in the main circuit is overloaded, and the coil of the contactor KM is cut off.




PLC hardware selection

The PLC hardware system consists of a PS307 (5A) power module, a CPU314, a digital input module SM321XDC24V and a digital output module SM322 DO32 X AC120/230/1A. The digital input module used has 32 input points, each of which is a group of 4, with 4 common terminals, with 1M, 2M, 3M,
4M means that the external control button (such as SB1, SB2) signal is sent to the corresponding input terminal through DC24V. The digital output module has 32 output points, each of which is a group of 8 points, and there are 4 common power input terminals. 1L, 2L, 3L, 4L means that external loads (such as KM) are connected between the common power input (such as 1L) and the output (such as Q4.1) through a power supply (such as AC 220V).

The screenshot of the program is as follows