I was commissioned by a company to write a program for a Siemens LOGO! industrial controller to control three cooling fans on their cooling network based on three different temperature sensors. The tricky part was they wanted their three fans to be utilized as one cooling unit. Therefore when the sensor signals, fan No.1 will start but after the signal dies and turns on again after a while, the program must switch to a fan that has not passed a working cycle before…This way all three fans will work the same hours and their life cycles increase…

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