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Chris Lott

I am the proprietor of Chris's Corner, an electrical engineer with more years in the field than I want to admit. I got hooked on electronics via Ham radio back in the 70s (WD4OLP / HL5ZJJ) and graduated from Georgia Tech in 1985. I've worked on all sorts of electronic projects, from government radars, NASA programs, industrial controllers, and consumer products. I've lived in South Korea for 20 years, where I've established a niche manufacturing company and an engineering consultancy. During pandemic I've sequestered myself here in my home office and laboratory, keeping busy on engineering projects and writing technical articles in my free time.
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Recent Posts

Circuit design for conductive inks- Part 8: Wrap-up

Sep 8, 2021 8:30:00 AM / by Chris Lott posted in conductive ink, flexible electronics, printed flexible electronics, circuit design

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This is the final article of the series on conductive ink experiments. Let's review the highlights of what we've learned, and summarize how we might use those lessons in a flexible circuit board design.

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Circuit design for conductive inks- Part 7: Transient analysis

Aug 18, 2021 8:30:00 AM / by Chris Lott posted in conductive ink, flexible electronics, printed flexible electronics, circuit design

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Transient Analysis

In this post we will examine some transient response tests as a function of trace resistance. And I've found the solution of the less-than-perfect serial port errors. This is part 7 of the series on conductive inks, and will wrap up the experiments portion of this series. The next and final post will be a summary of lessons learned.

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Circuit design for conductive inks- Part 6b: DC performance tests

Aug 9, 2021 8:30:00 AM / by Chris Lott posted in conductive ink, flexible electronics, printed flexible electronics, circuit design

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In this post we will wrap up part 6 by looking at some DC performance tests (apologies in advance for the fact that these tests are not very photogenic). And I'll also dig a little deeper in the mystery of the serial port errors from last time.

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Circuit design for conductive inks- Part 6a: Tarte-Py assembly and test

Jul 26, 2021 8:30:00 AM / by Chris Lott posted in conductive ink, flexible electronics, printed flexible electronics, circuit design

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The Tarte-Py boards have arrived, they've been assembled, and they've tested. In fact, one of them is running a series of tests right now as I type this post. How did it go? In summary, it was one of the worse board bring-ups I've experienced in recent memory. The troubleshooting process was both frustrating and enjoyable at the same time. It was also quite time consuming, which accounts for the tardiness of this post. Fortunately, the problems were eventually solved and the boards are now working. 

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Circuit design for conductive inks- Part 5c: MCU Test Board

Jul 5, 2021 10:56:20 AM / by Chris Lott posted in conductive ink, flexible electronics, printed flexible electronics, circuit design

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Today we will go over the hardware design of the MCU board, which I've named Tarte-Py: Tester for Automatic Resistive Trace Experiments in Python. The board follows closely in concept to the Pyboard as noted in Part 4, but with some slight circuit changes and big mechanical changes to better fit our application.

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Circuit design for conductive inks- Part 5b: Instrument setup

Jun 29, 2021 10:52:50 AM / by Chris Lott posted in conductive ink, flexible electronics, printed flexible electronics, circuit design

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In this article, I'll discuss the testing approach for this project. Since I'm basically lazy, the goal is to keep things as simple as possible and try not to reinvent the wheel.

Testing Approach

The gist of these tests is to take various parts of the circuit of interest, say a serial data link, and first observe it while its operating in the normal way. In this project, normal means with highly conductive copper traces. In the serial data example, this would mean checking the that data is not corrupted and perhaps watching the waveform on the oscilloscope.

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Circuit design for conductive inks- Part 5a: TraceR

Jun 21, 2021 8:00:00 AM / by Chris Lott posted in conductive ink, flexible electronics, printed flexible electronics, circuit design

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In this article, I am going to review the variable trace resistance simulator that I've designed for this project. I'll go over some design options and how I made my decision, and wrap up with the completed design, whose PCB is being produced even as I type.  In case you've just missed the blogs leading up to this point, you can find them here.

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Circuit design for conductive inks- Part 4: Making a reference PCB

Jun 14, 2021 8:30:00 AM / by Chris Lott posted in conductive ink, flexible electronics, printed flexible electronics, circuit design

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In the previous articles, we've taken a look at conductive ink PCB traces using a few back-of-the-envelope calculations. Now that we have a rough idea what to expect, it is time to get on with the fun part of this series -- building a real printed circuit board and testing how it behaves as we tweak the trace resistances.

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Circuit design for conductive inks- Part 3: Dynamic AC performance

Jun 7, 2021 8:30:00 AM / by Chris Lott posted in conductive ink, flexible electronics, printed flexible electronics, circuit design

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Last article we looked into the ramifications of using conductive ink PCB traces from a static, DC perspective. Today I'm going to consider the implications from a dynamic point of view. Most of the signal interfaces we use in microcontroller designs today drive very high impedance loads. The impact of increasing the trace resistance connecting to the input gate is an increase in the rise time. Let's take a look at that in more detail.

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Circuit design for conductive inks- Part 2: Static DC analysis

May 31, 2021 8:30:00 AM / by Chris Lott posted in conductive ink, flexible electronics, printed flexible electronics, circuit design

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During this series, I plan to learn about printed ink conductors primarily on my own, through analysis and experiments. Therefore I have intentionally avoided digging too deep into the details of how they are commonly used in the industry (an approach I wouldn’t recommend for someone doing this for a professional product). But I do know people are indeed using printed inks for a variety of circuits, so I don’t expect to find any big showstoppers in the analyses and experiments that follow.

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