LOGO! realizes intelligent alternating start and stop between two compressors

In industrial production, it is sometimes necessary for two compressors that share a power supply line to be able to start and stop alternately. When one compressor fails, the other can start automatically. Moreover, these two compressors need to be able to operate separately in manual or automatic mode.
Two operating modes


Manual operation


Only one compressor can be operated. For compressor 1, the selector switch must be set to "manual" (connected to I1), and the selector switch of the second compressor must be set to 0.


If you want to operate compressor 2 in manual mode, the selector switch must be set to "manual" (connected to I3) and selector switch 1 must be set to 0
Automatic mode


In automatic mode, the two compressors operate alternately. This requires setting both selector switches to "automatic" (connected to I2 and I4).


Actual application scenario


During the day, from 7 am to 6 pm, compressor 1 will operate if there is sufficient pressure. For this, a pressure monitor is connected to I5.


If there is still sufficient pressure


It will switch to compressor 2 between 6 pm and 7 am. However, before switching, the compressor must run for a while. For compressor 1, the preset running time is 50 seconds and for compressor 2 is 25 seconds.


If one of the compressors fails due to insufficient pressure


Switchover to the other compressor will occur automatically. Even if sufficient pressure is available again, this compressor can only be switched off if both selector switches are set to 0. Automatic mode must then be selected again.


If a response from I5 is triggered due to insufficient pressure


This is signaled via a fault light at Q5. The fault can be acknowledged via I6.


If the pressure remains below the preset value for more than 2 minutes


A flashing light appears at Q6. This alarm signal continues until sufficient pressure is available again.