Tag Archives: signal

Understanding bioelectricity


by Maurizio @ dev.emcelettronica.com:

Our body is built with biological tissue. The tissue that can generate or detect bioelectrical signals is called excitable tissue. Some examples of this tissue (and its cells) are: neurons and muscular tissue. Neurons are responsible of transmitting the excitatory bioelectrical signal to another neuron (forming nerves) or to a muscle tissue, gland or brain, while muscular cells are responsible of muscular contraction and distension. Some specialized cells generate bioelectric signals: optic receptors (eyes), muscular cells that transmit the feeling of pain, etc. Bioelectricity concerns the magnetic and electrical fields produced by organisms or cells.

Understanding bioelectricity – [Link]

Signal Generation with MATLAB. Example of DTMF in telephony


by  Maurizio @ dev.emcelettronica.com:

In mathematics a signal is a real function of a real variable f(t). In electronics it represents the evolution of a voltage (or a current) over the time and depends on the performances of the stage of the amplifier. Through a memory buffer, samples move to a digital-to-analog converter that produces a voltage signal, after an amplification stage that can limit the generation of the signal. A possible analysis consists of use Matlab with a PC sound card and an example of DTMF.

Signal Generation with MATLAB. Example of DTMF in telephony – [Link]

Researchers use voltage to control magnetic memory


by Amy Norcross @ edn.com:

A new way of switching the magnetic properties of a material using just a small applied voltage could signal the beginning of a new family of materials with a variety of switchable properties, according to a team of MIT-based researchers. The technique could let a small electrical signal change materials’ electrical, thermal, and optical characteristics.

Researchers use voltage to control magnetic memory – [Link]

View noisy signals with a stable oscilloscope trigger


by Dave Rishavy @ edn.com:

Noise on a signal creates a triggering challenge for test equipment, especially oscilloscopes. Because the instrument itself also contributes noise, small signals in the millivolt range need proper instrument settings prevent noise from overwhelming the signal of interest. Even with larger-amplitude signals, noise can create a condition where a stable trigger is difficult to achieve.

Oscilloscope have built-in features to help deal with the noise. These features can sometimes be buried in menus, or not well known by infrequent oscilloscope users.

View noisy signals with a stable oscilloscope trigger – [Link]

Transmission Line Terminations for Digital and RF signals

by w2aew:

An introduction to why and when terminations are needed for transmission lines in both high speed digital applications and RF applications. 50 ohm termination examples are given, but the principles apply for other line impedances as well. The basic operating principles of signal propagation down a transmission line and the effects of reflections coming from improperly terminated are covered. Examples for digital-like signals as well as RF signals are given. A description and examples of what is meant by Standing Waves is also given. As a bonus, the properties of quarter wavelength transmission lines in RF applications is also presented.

Transmission Line Terminations for Digital and RF signals – [Link]

Kidogo: 8 channel USB Digital Signal Injector

Dilshan developed a 8 channel USB digital signal generator and an open source Windows application called Kidgo Player to drive it. The hardware is basically just a PIC18F2550 USB breakout board used to provide 8 digital outputs for his software. The Kidgo Player’s source is available on GitHub, and has the following features – [via]

  • Save waveforms and settings as binary file (KDF file) or export waveform as a text file
  • Playback controls such as “Play to segment

Simple Signal Software Filter (with Python)

Scott writes:

It’s time for a lecture. I’ve been spending a lot of time creating a DIY dlectrocardiogram and it produces fairly noisy signals. I’ve spent some time and effort researching the best ways to clean-up these signals, and the results are incredibly useful! Therefore, I’ve decided to lightly document these results in a blog entry.

Here’s an example of my magic! I take a noisy recording and turn it into a beautiful trace. See the example figure with the blue traces. How is this possible? Well I’ll explain it for you. Mostly, it boils down to eliminating excess high-frequency sine waves which are in the original recording due to electromagnetic noise. A major source of noise can be from the alternating current passing through wires traveling through the walls of your house or building. My original ECG circuit was highly susceptible to this kind of interference, but my improved ECG circuit eliminates most of this noise. However, noise is still in the trace (see the figure to the left), and it needed to be removed.

Signal Filtering with Python – [Link]

gilbertojunqueira.com writes:

There are many times where you would like to “stabilize

Modeling of analog part for DDS3 signal generator

scienceprog.com writes:

When building AVR DDS2 signal generator there were lots of discussions about signal conditioning in analog part of device. First argument was that LM358 wasn’t the best choice for this purpose. Another one pointed to sine wave that weren’t smooth enough.

As you can see there are some dents on it. Other waveforms also are distorted especially when higher voltages are selected. This definitely asks for better analog part. Some people suggested to replace LM358 with OPA2134, but it seems to be quite expensive choice. In my opinion low noise general purpose op-amp can be great too. I’m gonna give a try to Texas Instruments TL074 low noise op-amp. It is low power, high slew rate (13V/us) IC – almost five times faster than LM358 and for same reasonable price.

Modeling of analog part for DDS3 signal generator – [Link]

IR protocol analyzer

ostan.cz writes:

IR protocol analyzer is a universal application for automatic decoding several types of infrared remote control protocol packets. The application uses microphone input of a soundcard to capture infrared signal from a remote control. As a consequence, the hardware receiver is minimalistic and easy to build; just plug a phototransistor to input of your soundcard, that’s all hardware you need.

Application processes IR signal from a remote control and compares it with its own database of known protocols. When a match is found, packet is decoded and its characteristic is displayed to user (including protocol name, description, decoded data and graph with timing).

IR protocol analyzer – [Link]