There are certainly strong similarities between these two approaches to controlling equipment, and with the circuit described here we blur any remaining distinction still further. The Pico PLC employs only standard components and the necessary software development tools are available free on the Internet for private users.A distinction is frequently drawn between microcontrollers and PLCs (programmable logic controllers) used in industrial control applications. The first thing that is apparent is that the PLC is designed for industrial use: in particular this usually means a supply voltage of 24 V. Also, the circuit will be robust against supply polarity reversal, voltage spikes and short circuits.We find a further difference in the software. A PLC runs a monitor program which controls the sequence of events executed. This involves, among other things, the use of interrupts, software timers and dealing with various interface protocols (frequently RS-232 or CAN bus).