Low-Drop Series Regulator Using a TL431 (EE Tip #134)


You likely have a stash of 12-V lead acid batteries (such as the sealed gel cell type) in your lab or circuit cellar. Below is a handy tip from Germany-based Lars Krüger for a simple way to charge them. A … Continue reading


What Is Emissivity? (EE Tip #133)


All objects radiate infrared energy. The warmer an object is, the faster the molecules in the object move about, and as a result the more infrared energy it radiates. The wavelength of this radiation lies roughly between 0.5 and 100 … Continue reading


Measuring Jitter (EE Tip #132)

Figure 4—Time interval error (TIE) is another way to measure jitter. Here, the actual transitions are compared to a reference clock, which is supposed to be “perfect,” providing the TIE. This reference can be either another physical signal or it can be generated using a PLL. The measured signal’s accumulated plot, triggered by the reference clock, also provides the so-called eye diagram.

Jitter is one of the parameters you should consider when designing a project, especially when it involves planning a high-speed digital system. Moreover, jitter investigation—performed either manually or with the help of proper measurement tools—can provide you with a thorough … Continue reading


DIY Single-Board Computer (EE Tip #131)

Photo 2—This is the N8VEM in its $20 stand-alone incarnation. Even without any other boards, this SBC provides sufficient I/O and storage options to be a full-fledged CP/M computer.

In the early 1990s, nostalgic users wrote software emulators to relive the “vintage” experience of their old Commodore 64 or Apple II. Others preferred the actual hardware and began collecting classic computers. As their old machines occasionally broke down, people … Continue reading


Battery Charger Design (EE Tip #130)

Figure 1: This lead-acid battery charger uses Texas Instruments’s UC2906 IC.

It’s easy to design a good, inexpensive charger. There is no justification for selling cheap, inadequate contraptions. Many companies (e.g., Linear Technology, Maxim, Semtech, and Texas Instruments) supply inexpensive battery management ICs. With a few external parts, you can build … Continue reading


Active ESD Protection for Microcontrollers (EE Tip #129)

Figure 2—Typical ESD protection circuit, as found in an Atmel microcontroller

Microcontrollers need to be protected from of electrostatic discharge (ESD). You can use the circuit described in this post when you have an application requires a greater degree of ESD protection than what you get from an IC on its … Continue reading


Op-Amp Versus Comparator (EE Tip #128)


Practically every lecture course or textbook on electronics describes how to use an operational amplifier as a comparator. Here we look at the possibility in more detail, and see how it can often be a very poor idea. The idea … Continue reading


Build an Adequate Test Bench (EE Tip #127)

Test Board

It’s in our makeup as engineers that we want to test our newly received boards as soon as possible. We just can’t wait to connect them to a power supply and then use our test bench equipment (e.g., generators, oscilloscopes, … Continue reading


A Wire Is an Inductor (EE Tip #126)


I’m confident you know that you should keep wires and PCB tracks as short as possible. But I’m also sure that you will underestimate this problem fairly frequently. Remember that 1 cm of a 0.25-mm-wide PCB track is roughly equivalent … Continue reading


Triangulation, Trilateration, or Multilateration? (EE Tip #125)

Triangulation - EL-Valens-Feb11

Local Positioning System (LPS) and GPS (not just the US system) both use several transmitters to enable a receiver to calculate its geographical position. Several techniques are possible, each with its advantages and drawbacks. The important thing in all these … Continue reading


A Fundamental Rule of Grounding (EE Tip #124)


Quantum mechanics notwithstanding, our world is analog. And so despite our fascination with everything digital, we need interfaces to provide bridges for our analog reality to cross over to the digital paradigm and then back again. One may ask: Is … Continue reading


Wireless Product Regulations (EE Tip #123)

CE Mark

Are you working on a wireless design that you’d like to bring to market? If so, be sure to anticipate regulatory constraints right from the start. Planning upfront will save you a lot of time, money, and hassle. Electrical engineer … Continue reading


DDS Basics (EE Tip #122)

Figure 1: The most basic digital signal generator is built with a simple binary counter. Its output sequentially
addresses the rows of a memory, which holds the successive points of the output signal. It is then converted to an
analog signal and filtered.

The simplest form of a digital waveform synthesizer is a table look-up generator (see Figure 1). Just program a period of the desired waveform in a digital memory (Why not an EPROM for old timers?), connect a binary counter to … Continue reading


Using Arduino for Prototypes (EE Tip #121)


Arduino is an open-source development kit with a cult following. Open source means the software and hardware design files are available for free download. This begs the question of how the Arduino team can turn a profit, and the answer … Continue reading


Basic Goertzel (EE Tip #120)

Figure 1: 
Figure 1—The signal flow of the basic Goertzel transform produces an output (y0) for each sample processed. The output is a combination of the current ADC sample added to the product of the previous output (y1) multiplied by a constant minus the previous output (y2). After a block of samples has been processed, the sum of the squares of y1 and y2 are computed to determine the relative amplitude of a particular frequency.

The basic Goertzel transform, which has been around since 1958, was derived from the discrete Fourier transform (DFT). It’s an extremely efficient method of detecting a single frequency component in a block of input data. Figure 1 depicts the signal … Continue reading