Texas Instruments 5TI PLC Programmer

This page starts with a simple question: What is a PLC or Programmable Logic Controller ? The answer: A device used to automate monitoring and control of industrial plant. You could think about a computer without a keyboard or display unit running the same program day and night using sensors and actors like switches and relay's. An example could be found in the crossing lights in your town. 

During program changes or maintenance schedules the operator uses a socalled Programmer to communicate with the PLC. Texas Instruments is together with companies like Rockwell Automation and Omron one of the big players in the PLC market. About 1976 they introduced this medium sized 5TI Programmer.

This 5TI Programmer looks familiar to you ? Please compare it with SR-20 desktop calculator introduced in the year 1973. Some parts of the housing and the display are really identical, a cost reduction continued with the later Model 510 Programmer.

Inside the Programmer is totally different to a SR-20. You'll find a sandwich of three different printed circuit boards (PCB). The first PCB carries the keys and the functional LED's and a second one the display borrowed from the SR-20 and some driver circuits.

The surprise of the 5TI Programmer is the third PCB ! Instead of a smart microcontroller there is discrete logic with an overall count of 39 integrated circuits.

If you have additions to the above article please email: joerg@datamath.org.

© Joerg Woerner, December 5, 2001. No reprints without written permission.