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Microchip introduced the ATmega128Dx in three variants: -DA, -DB, and -DD. These 8-bit microcontrollers can run at 5 volts and have several compelling features. While no "official" Arduino board exists based on these chips, an open-source package adds support to the Arduino IDE: DxCore. I liked the chips so much that I featured them in a Workbench Wednesdays episode.   Unlike the ATmega328p found in the venerable Arduino Uno or Nano, the newer ATmega128Dx chips have a "MegaAVR" core. Frank ...
Since last March 2020, I have been live-streaming three days a week. My streams are all electronics related but include retro computer repairs, soldering kits, Arduino coding, explaining measurements, and other electronics stuff. Several of the recent Workbench Wednesdays episodes have been a result of a live stream. Another outcome from these streams is that my soldering skill has increased significantly. Not just because I am practicing more, but because constantly being watched and critiqued ...
Over the past several months, I have been learning about and repairing 8-bit computer and video game systems. So far, I have worked on the VIC-20, C64, ZX-81, Apple II, and have been learning about the TI 99/A.   It always amazes how much of these early computer systems were built almost entirely with standard 7400-series (LS and HC) chips.   Occasionally, I need to replace a 7400-series chip. (I always hope it is one of those and not one of the ASICs!) While looking for modern repla ...
This weekend I went to build a circuit for use in an upcoming video. There were two components I was confident that were in my parts kit: a 555 timer and a counter. Now, I did not know which counter I had, but I assumed I must have at least one decade counter in my pile of ICs. Imagine my surprise when I realized that I had no 555 timers and only a single type of counter. And that counter was a johnson-counter designed to drive common cathode 7-segment displays. To make things worse, the only 7- ...
The MP730026 DMM supports BLE communication. However, I quickly learned that the software offered by Multicomp Pro has significant limitations. So I set out to find a cross-platform solution, which leads me to Python. In the MP730026 DMM BLE Tutorial, I covered how to install the Bleak Python module, find the meter's MAC address, and receive update messages from the DMM. In this post, I explain how the bytes being received are getting turned into a string value.   If you just want to know ...
  At a glance, the Multicomp Pro MP730026 seems like a typical DMM. And it is! It measures voltage, current, frequency, temperature (with included K-Type thermocouple), and even features a white LED to act as a work light. The non-typical feature that caught my attention is its Bluetooth Low Energy (BLE) support.   Overall I like the meter. It is an excellent general-purpose DMM. After using it for a couple of months, I have discovered only three things I dislike about it. The first ...
Every electronic device includes a DC-DC converter for its power supply. That supply might come from a USB port, a "brick", a wall-wart, or in larger systems, there could be multiple point-of-load converters scattered around a single circuit board.   When you have a DC voltage that you need to change into another voltage, you have two options: a linear regulator or a switch-mode power supply design. Let's take a look at the difference between the two and a couple of cases where you might c ...
Analog-to-digital converters (ADCs) enable a wide range of electronics applications. They make it possible for devices to interact with their environment. Most sensors convert a physical quantity into a voltage.  While it is certainly possible to build circuits that make use of that analog value, very often it is necessary to work with that voltage digitally. As the name implies, an ADC converts analog signals into a digital format. For example, if you put 5 volts into an analog-to-digital ...
Semiconductor Measurements element14 Presents  |  Bald Engineer: James Lewis' VCP Profile |  Workbench Wednesdays   A good MOSFET datasheet is excellent when it contains detailed information. However, too much information might mean there is too much data to sort through. If you want to build a low-frequency switch, what is the minimum information you need to understand? As it turns out, you only need a few pieces of data from a table and to look at a couple of MOSFET cu ...
One of my hobbies is collecting vintage computers. Computers in my collection include the Apple IIgs, Atari 400, TI 99/4A, Commodore 64 and Sinclair ZX-81 to name a few of the popular ones. Like all electronics, these systems contain capacitors. Anyone who has collected retro game systems, computers, or audio gear knows to look for caps that have leaked their electrolyte. But, what if you cannot see visual damage, what measurements can you make to verify if an aluminum electrolytic has reached i ...
Capacitor Replacement on a Commodore 64 - A Lesson in Through-Hole Soldering WorkBench Wednesdays |  Bald Engineer: James Lewis' VCP Profile |  Project Videos     In WorkBench Wednesdays , one of my mini-projects was to replace the capacitors in a Commodore 64. In the video, I only had time to replace about half of the decoupling capacitors. Later I'll go back and finish the rest. This post discusses why I picked the capacitors used in that project.   For organi ...