A linear isolation amplifier from Silicon Labs app note. Link here (PDF)
Analog circuits sometimes require linear (analog) signal isolation for safety, signal level shifting, and/or ground loop elimination. Linear signal isolation is typically difficult to implement, costly, and often exhibits mediocre performance. While the design community thirsts for a flexible and inexpensive linear isolator solution, it is the analog isolation amplifier (ISOamp) that most often captures the socket.
This article is broken into two parts. First comes the “Oscar” preselector/preamplifier. As I said, I intended it to be either part of the overall receiver or used as a standalone where desired. The second part deals with the WBR upgrades. Both designs were built using the same techniques and I’ve tested both and found that—especially in concert—they do about as well as some of my boat anchors! So if your soldering iron is ready, I’ll start by describing “Oscar.”
However, what you might notice is the presence of image products in the waterfall. The processing of the signal suppresses all but the very strongest of these so they don’t appear as audio but it is mighty confusing when they are on the waterfall but actually not there (if you see what I mean)!
I am in the process of building a QSD or Tayloe Detector, which should provide better rejection of images. I have breadboarded one of these, it works but not very well. I think that this might be due to the length of leads I have on the breadboard so I am trying to use Eagle CAD to design a circuit board to overcome these problems.
Vasily Ivanenko has written an article detailing his AF dummy load project:
I’ll describe a simple 8, or 4 Ω dummy load to test your home brew guitar power amplifiers.
Low cost 16 Ω / 25W wire wound, aluminum shell, chassis mount resistors seem abundant. I got mine on eBay. Wire wound resistors vary in quality, design and tolerance. Some even exhibit low inductance by winding with an Ayrton-Perry bifilar technique. Resistor tolerances range from 10% down to ± 0.5 % + 0.05 Ω. Typical manufacturer power ratings are done at 25C, however, these devices are meant to sit on a heat sink when used and that’s why the aluminum housing contains 2 relatively large mounting holes.
In the first installment of this series, we discussed why we’re building a Direct Conversion receiver and talked about some basic ideas. In this installment, we explore what it takes to make the leap from a printed schematic to something physical that works. Follow along!
App note from OSRAM on their ALS device SFH5701, its operation and application method. Link here (PDF)
The SFH5701 is a small, two-wire, linear output current ambient light sensor (ALS) with current amplifier and dark current compensation. The ALS is capable of resolving a wide range of ambient light levels (10 mlx – 10 klx) tailored to the spectral response of the human eye and operational from -40 °C to 100 °C.
USB MIDI controllers (such as Launchpad Mini Mk II for example) are common and often quite low in cost.
To interface such a controller with a Eurorack synth system, often a host computer and a MIDI to CV interface might be used. The host computer would take USB MIDI data from the MIDI controller, perhaps store and manipulate that data in some way (e.g. a sequence), using a MIDI to CV converter to then control a Eurorack synth system.
It would be useful to use USB MIDI controllers with Eurorack synth systems without needing a computer and MIDI to CV interface in between the two.
Teensy 3.6 is a great microcontroller that can be programmed using the Arduino IDE. A very useful feature of the Teensy 3.6 is the USB host port.
I have done several pen and laser machines lately, so I decided to create a custom PCB for Grbl_ESP32 for these types of machines. This is a small (70mm x 60mm) PCB with all the features a pen plotter or laser cutter/engraver would need.
These typically use stepper motors for the X and Y axes. On pen plotters, the Z axis is controlled by a servo or solenoid. On lasers you need an accurate PWM for laser power control.