A casual observer might think that wireless systems consist primarily of filters connected by the occasional bit of circuit. Block diagrams of transceivers often include as many filters as any other function. This is true at the system level, just as it is at the circuit level — and many circuits behave in a filter-like way, whether intended to be a filter or not! That makes understanding filter basics important for wireless success.
This fourth installment will examine the more complex circuits from the book, “555 Timer IC Circuits” by Forrest Mims. Some will use the PIC replacement from Part 1, while others will develop specific programs using a PIC to emulate a particular implementation of a 555.
For audiophiles, musicians, and ham radio operators, the soft glow of the vacuum tube filament is not only an indication of function, but a nostalgic trigger for memories of simpler times. Though they may have been outpaced by tiny transistors and integrated circuits, these workhorses still may have something to offer in many modern devices.
Here’s a quick beginner-friendly tutorial that shows you how to interface and read data with the popular serial protocol, I2C. In particular, we’ll be reading data from the NXP MPL3115A2 altimeter/barometer/temperature sensor. The principles found here can also be applied generically, even to your ambifacient lunar wane shaft positioning sensor of your turboencabulator.
Inspired by Forrest Mims and his Mini-Notebook series, we'll detail the emulation of a 555 or 556 using a PIC in several different circuits. The particular implementation this time covers both monostable and astable modes, and the PIC does not have to be reprogrammed in any way.
For low frequency control, switching, and DC power, it is possible to get the job done without worrying too much about wiring and cabling practices. However, when RF gremlins begin to appear, suddenly, a whole new set of cautions and constraints gets piled on to your “simple” project. This article provides an overview of shielding, including some practices you should know as a defense against these gremlins.
Much as we learn about ourselves from our mistakes, we can learn a great deal about transformers from their imperfections.
In the US, the DC volt is legally defined by the Josephson array — a super conducting quantum device with a highly repeatable output voltage. Banks of standard cells and temperature-stabilized zener diode references are used by the National Institute of Science and Technology (NIST) to calibrate DC meters for scientific and industrial customers. So how is the AC volt defined?
When RF energy travels in a transmission line and encounters a load or different type of line, the resulting reflections create standing waves of voltage and current, just as water waves do when they encounter an obstruction. This can create problems with digital signals and can result in extra losses. However, there are several techniques for dealing with these reflections.
The digitally-programmable potentiometer (DPP) is a mixed signal, system-level control device performing a component-level function. The potentiometer adds variability to the analog circuit, while the digital controls add programmability. The DPP brings the high speed, programming, computation, and control of a processor to the variation of the potentiometer in a wide array of analog applications.
