Now that I’ve retired, I’ve started experimenting with some of the analog subjects that I haven’t done much with since school back in the seventies. To begin with, I started with op-amp circuits; specifically, Colpitts oscillators. I built the circuit on one of those plug-in ‘protoboards,’ a ±15V power supply, an oscilloscope, and a multimeter. For my experimentation, I was using a trim pot. I would adjust until oscillation began, then power down, pull one end of the trim pot, measure the resistance, then re-connect, power up again, and continue adjusting until I reached the other end of the resistance range, where the oscillation would cease. I would then repeat the resistance measurement. That procedure was not ideal. In addition to the multiple tedious steps, adjusting a trim pot can be a pain. Enter my potentiometer box.
Sometimes called a VI curve tracer or an IV curve tracer, this oscilloscope Octopus generates AC excitation across its two leads and then displays a voltage vs. current plot in real time. The resulting plot can be used to track down opens, shorts, and noise in a component, as well as measure the breakdown voltage and phase relationship between voltage and current. The circuit has been around just as long as oscilloscopes, but this Octopus is a small battery-operated instrument with its own display. Instead of an octopus’ worth of jumbled cables, there’s just a pair of test leads.
This article discusses basic theory on the decibel unit and its role in electrical measurements of power, etc. It also describes the construction of an RF power meter which in the past has been difficult to use and expensive to own. With the breakthrough of new ICs in recent years, most of the former problems and expense have been eliminated. This is a simple and inexpensive unit to build, but has the accuracy, resolution, and dynamic range that was only obtainable in lab quality test equipment a decade or so ago. This kind of test equipment is almost mandatory for amateurs, radio frequency work, or test equipment calibration. Also, when built as described, it’s a very professional looking piece of gear that anyone would be proud to display on their test bench.
For those who experiment and build with vacuum tubes, an adjustable regulated benchtop high voltage power supply is essential. Many circuits for such units have been described that themselves use tubes. It’s nice to be consistent, but we can save some bench space and a few watts by using semiconductors in such a unit.
The oscilloscope is my go-to measurement instrument in every electronics project I work on, helping me debug and fine-tune hardware and software projects. In this article, I’ll show how you can get started with a simple-to-use scope you probably already have. Best of all, it’s free! When you graduate from this simple scope, you can purchase a more powerful scope using the exact same user interface. I think the free scope control software, Waveforms, is the simplest to use, most feature-rich pro-level software of any of the available options. Using a sound card as the hardware interface with Waveforms puts a simple yet powerful scope in your hands for free.
One thing you want to check before you start a long 3D print job is to verify you have enough filament on the spool to complete the print. You don’t want to come back to your printer at the end of a two-day run (as I have!) only to discover that the machine ran out of filament and the top part of the object is missing! This project describes a dedicated “spool scale” that provides a real time readout via an Arduino of just how much material you have left.
Work areas usually have multiple power strips ganged together and connected to the same outlet. Various devices are connected to these strips, including computers, lights, coffee pots, space heaters, etc. Environmentally conscious persons ask, “How much power does my work area consume?” Safety conscious persons ask, “Am I overloading my circuit?” Calculating the answers requires two basic measurements: the voltage supplied to the circuit, and the amperage consumed by the circuit. Measuring AC voltage and, particularly, amperage with a multimeter is a potentially dangerous diagnostic for laypersons.
Wouldn’t it be nice to have a self-contained volt/amp meter that displays the values on a webpage?