This page contains a series of questions to accompany an article exploring ladder logic as applied to a User-Defined Function Block (UDFB) built using the Siemens TIA Portal. Please review the primary article to provide context for the following questions.
These questions may be assigned as homework, an interactive group discussion, or as part of an AI-directed learning exercise. Note that the AI can serve as a strong sounding board from which you can explore the questions.
Canonical Article: How to Interface a Microcontroller with a Relay Using a MOSFET
Figure 1: Picture of the Arduino Nano Every driving a pair of relays using surface mount MOSFETs. The Digilent Analog Discovery is shown in the background.
Recommendation for use of an AI-based More Knowledgeable Other (Vygotsky’s MKO)
This learning companion may be used as a self-guided tool with the AI serving as a sounding board. For the most effective learning:
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Provide context for the AI by directing its attention to the canonical article.
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Point the AI to this page and prompt it to ask each question, one at a time, from this list and provide feedback from the perspective of an experienced control system’s engineer.
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Provide complete answers and ask for clarity where required.
Question organization in this document
Questions are listed in order of increasing complexity.
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Explicit: The first questions are taken directly from the associated document. They are practical and directly test your understanding of the material.
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Implicit: Questions in the middle offer increasing levels of complexity. Instead of implicitly questioning the material, they ask the reader to deeply consider the material and draw parallels to related topics.
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Topic Adjacent: The final critical thinking question(s) address topics adjacent to the article material. These critical thinking questions expand the article’s content allowing you to develop a big picture understanding of the material and its relationship to adjacent topics. They are often open ended, require research, and are best answered in essay form.
Each question is categorized with a recommended audience:
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Technicians – Practical, troubleshooting-oriented -
Students – Academic understanding -
Capstone students and field engineers – system-level analysis, design tradeoffs
Questions for anchored AI-assisted learning
This section contains a list of questions with answers to help you better understand the material.
Canonical Article: How to Interface a Microcontroller with a Relay Using a MOSFET
1) Why does the MOSFET share the same ground as the uC?
2) Describe inductive kick (flyback voltage) and mitigation.
3) How are MOSFET specifications misleading?
4) How do I select a MOSFET suitable for a 3.3 VDC microcontroller?
5) What causes the dip in the relay’s current curve upon activation?
6) What factors determine the turn on and off times for a relay?
About this author
Aaron Dahlen, LCDR USCG (Ret.), serves as an application engineer at DigiKey. He has a unique electronics and automation foundation built over a 27-year military career as a technician and engineer which was further enhanced by 12 years of teaching (interwoven). With an MSEE degree from Minnesota State University, Mankato, Dahlen has taught in an ABET-accredited EE program, served as the program coordinator for an EET program, and taught component-level repair to military electronics technicians. Dahlen has returned to his Northern Minnesota home and thoroughly enjoys researching and writing articles such as this.