Editing Programmable logic controller (section)

=== Microcontrollers ===
A [[microcontroller]]-based design would be appropriate where hundreds or thousands of units will be produced and so the development cost (design of power supplies, input/output hardware, and necessary testing and certification) can be spread over many sales, and where the end-user would not need to alter the control. Automotive applications are an example; millions of units are built each year, and very few end-users alter the programming of these controllers. However, some specialty vehicles such as transit buses economically use PLCs instead of custom-designed controls, because the volumes are low and the development cost would be uneconomical.<ref name="McMillan 1999">{{cite book |first=Gregory K. |last=McMillan |editor-first=Douglas M. |editor-last=Considine |title=Process/Industrial Instruments and Controls Handbook |edition=Fifth |publisher=McGraw-Hill |date=1999 |isbn=0-07-012582-1 |chapter=Section 3: Controllers }}</ref>