Christopher Semanson

Interfacing to devices such as our smartphones, appliances, and cars have become the cornerstone of high end industrial design.  Smooth, polished interfaces that have once found themselves limited to high end devices such as smart phones, have now found their way on commodity designs that we often use on a daily basis.  The motivation for this includes a wide variety of positives that all stem from removing mechanical button from your user interface. It allows industrial designers to get very creative with the way they lay out and design their interfaces for things traditionally not as aesthetically pleasing such as a washing machine interface. Lastly, and probably most importantly, you gain a nominal cost reduction on a per button basis as the button is not a membrane or mechanical switch assembly; these usually require assembly time which is only exacerbated during high volume commodity designs.  With these benefits being evident, it is no wonder you see capacitive touch interfacing being introduced to more than just our smartphones.  However, a good design with capacitive touch isn't as simple as replacing the buttons on your legacy oven interface and hoping it will work. A successful design is rooted in the center of:

• Understanding the technology behind the peripheral as each Microcontroller's (MCU) implementation is just a little bit different, and they would say unique.
• Understanding parasitic capacitance and how things like floating wires influence the system.
• Understanding the software that controls the peripheral hardware block; and
• Understanding how to design your product such that when undergoing traditional EMC testing (to gain that coveted CE mark), you are able to breeze right past it.

The key points addressed will first be design related, topics such as: how such a device operates, and the components that make up a capacitive touch system.  Then move on to user feedback, highlighting how simple things like driving multiple LEDs off of an unregulated supply, or leaving LED traces floating could negative effect system performance.  Next, system level testing to pass IEC 61000 series testing will be touched on. Problems related to obtaining the coveted CE mark are centered on conducted susceptibility, or how the sensor interface reacts when introducing noise to the system.  Lastly, after understanding the general design concerns the article will provide a checklist for you.  This is because each microcontroller (MCU) manufacturer implements this technology in their own way, through application notes, layout guides, and software implementation.

Biography:

Christopher Semanson has grown up in the metro Detroit area. He recently took employment down in North Carolina at Renesas Electronics America. He is working with both Electrical System’s applications for general purpose, and more recently functional safety systems for automotive power management circuits (PMICS).  He previously worked his day job at Ford Motor Company, doing Powertrain Controls, Systems Engineering, and Advanced Driver Assistance (ADAS) Features. He was very instrumental in helping Professor Mark Steffka establish a well-known EMC lab course at the University of Michigan at Dearborn.  He holds a masters of Electrical Engineering, and a Bachelor of Science in Electrical and Computer Engineering from the University of Michigan at Dearborn.