The Siemens LOGO! Programmable Logic Controller (PLC) may be programmed in Ladder Diagram (LD) or Function Block Diagram (FBD) using the LOGO! Soft Comfort software.
Many LD programming environments present the timer’s Q output as an extension of the block. This is not true for the LOGO. As seen in Figure 1, there are no right-hand connections to the block.
This article is part of the DigiKey Field Guide for Industrial Automation
Location: Program It → PLC → Siemens LOGO!
Difficulty: 
Engineer — difficulty levels explained
Author: Aaron Dahlen | MSEE | Senior Applications Engineer, DigiKey
Last update: 09 Mar 2026
Figure 1: Siemens LOGO! ladder logic program featuring a time on delay timer.
To use the timer’s output, we must instantiate a contact and point it to the appropriate timer. An example is shown in Figure 2 where a normally open contact (red highlights) is being configured to use the T001 timer’s output.
Figure 2: The red highlighted contact is being configured to respond to the warmup timer.
Please let us know if you have any questions about the Siemens LOGO PLC. Recommend a new thread for your questions unless you would like to know more about the timers as programmed in ladder logic.
Sincerely,
Aaron
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About This Author
Aaron Dahlen, LCDR USCG (Ret.), is a Senior Applications Engineer at DigiKey in Thief River Falls. His background in electronics and industrial automation was shaped by a 27-year military career as both technician and engineer, followed by over a decade of teaching.
Dahlen holds an MSEE from Minnesota State University, Mankato. He has taught in an ABET-accredited electrical engineering program, served as coordinator of an electronic engineering technology program, and instructed military technicians in component-level repair.
Today, he has returned to his home in northern Minnesota, completing a decades-long journey that began with a search for capacitors. Read his story here.