Abstract: It is incredible how many programmable logic controls (PLCs) around us make our modern life possible and pleasant.Machines in our homes heat and cool our air and water, as well as preserve and cook our food. This tutorial explains the importanceof PLCs, and describes how to choose component parts using the parametric tools on the Maxim's website.A similar version of this article was published February 29, 2012 in John Day's Automotive Electronic News.