Tutorial on Passive Filters, Data Transmission and Equalization

February 13, 2012 Shahriar 36 comments
EyeDiagram

In this episode Shahriar explores the world of filters! Starting from a simple lumped RC filter, he briefly covers the theory before moving onto measurement techniques. The bandwidth of the filter is verified experimentally in the time domain. A more complex RLC band-stop filter is also demonstrated with a tune-able inductor which is measured using an RLC meter. Using a Rigol spectrum analyzer with built in tracking generator and an active probe, the frequency response of the filter is measured. Several other packaged filters are also demonstrated and a microwave band-pass filter is disassembled to reveal its internal construction. 

Moving onto “undesired filters”, a Tyco backplane board is presented and the bandwidth limitation of the backplane traces are measured. A Xilinx FPGA board equipped with a Virtex II PRO is used to generate a 1.5Gbps PRBS data stream through the Tyco board. After observing the frequency composition of the date, pre-emphasis equalization is used to compensate the backplane frequency limitations. Eye diagram measurements verify the benefit of pre-emphasis equalization to combat inter-symbol-interference (ISI).

I would like to acknowledge my friend and colleague, Dr. Timo Pfau for his expertise in setting up and configuring the Xilinx FPGA board.

 

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Tutorial on Linear and Non-linear Circuits

October 17, 2011 Shahriar 13 comments
IIPS Diagram

  

In this episode Shahriar investigates the impact of linearity and distortion on analog circuits. The source of a non-linear input/output characteristic is presented in three different domains: mathematical, time domain and frequency domain. After the theoretical discussion, a sample circuit is built and tested to illustrate real time signal distortion. The criteria for measuring non-linearity is also presented. Furthermore, the importance of a two-tone test for bandwidth limited circuits is shown theoretically and experimentally. There is another quiz in this episode! Please discuss the answer on the forum or in the comment section.

 

Circuit Design ,

9-DoF AHRS Sensor Board and RGB LED Matrix Demo

September 18, 2011 Shahriar 10 comments
RGB Matrix

 

In this (experimental) episode Shahriar demonstrates two embedded-electronic circuits available for purchase from Sparkfun Electronics. The demos illustrate some of the capabilities of these circuits along with a short instruction on how to interface and operate them. All the code for the AHRS demo and the RGB Matrix demo are available to download.

The first demo is of a 9-degree of freedom (9-DoF) sensor board equipped with three dimension of linear acceleration (accelerometer), angular acceleration (gyroscope) and magnetometer. Using the combined information from these sensors an Attitude and Heading Reference System (AHRS) data can be extracted. The demo shows this system in action using customized Matlab functions. 

The second demo demonstrates the ease of use of an RGB LED Matrix equipped with an SPI interface. A sample C code written for a Microchip PIC18F2455 is used to draw some simple animations.

This is an experimental episode to judge the level of interest in these type of demo videos. Please leave feedback!

 

General ,

Rigol DP1116A and DP1308A Programmable Power Supply Review

August 30, 2011 Shahriar 29 comments
Rigol Power Supplies

 

In this episode Shahriar reviews the brand new Rigol DP1116A and DP1308A programmable power supplies. Furthermore, the power supply features are compared against an Agilent dual output power supply.

“DP1308A & DP1116A are high-performance programmable linear DC power supply. They have excellent features including timed outputs and tracking capabilities; extremely clean  ripple and noise, comprehensive over-voltage, over current, over-temperature protection, a large and clear user interface, super performance specifications,and  multiple standard interfaces. The DP1308A & DP1116A meet the requirements of various forms desktop and integrated system testing. DP1308A & DP1116A are widely used in research and development, education, industrial control, mobile communication, and product testing, etc.”

The MSRP for both products is $849. Rigol offers a 30 day no-questions-asked return policy and a 3 year warranty. They also provide an excellent local technical support out of tropical Cleveland, Ohio.

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Equipment Review

Op-Amps, PWM and Ignition Coils Tutorial

August 21, 2011 Shahriar 17 comments
Op-Amp

 

In this episode Shahriar discusses methods for generating a pulse-width-modulated (PWM) signal entirely in the analog domain by employing operational-amplifiers (Op-Amps). A total of four op-amps from a single power supply are used in unity-gain negative feedback, astable positive feedback, integrator and open-loop comparator configurations. The theory of operation as well as measurement are also presented. This episode also includes a quiz. Please post your answers in the comment section.

As a final experiment, an ignition coil is used to generate in excess of 20k volts! The combination of the PWM circuit and the ignition coil provides a stand-alone fully analog high voltage power supply.

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Circuit Design , ,

Frequency Generation: Crystals and Ring Oscillators

August 8, 2011 Shahriar 36 comments
Crystal

 

In this episode Shahriar takes a look at the challenges associated with signal generation for the purposes of timekeeping. More specifically he digs deep into the workings of crystal oscillators and even takes apart some vintage crystals to reveal whats inside! He also shows how this type of circuits can be characterized and compares the performance of a crystal oscillator with that of a ring oscillator under temperature and power supply variations.

 

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Circuit Design, General , ,

Camera Flash Circuit and Nixie Tube Tutorial

June 12, 2011 Shahriar 6 comments
Nixie Tube

 

In this episode Shahriar explores the principle operation of a camera flash circuit. The flash circuit is analyzed at the schematic level and through measurements. He then moves on to power a nixie tube using this circuit and calculates the efficiency of the DC-DC converter for this type of application. There is also a little quiz in this episode! Whoever solves the quiz will chose the topic of the next video.

 

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Saleae Logic and Logic16 Product Teardown

May 31, 2011 Shahriar 5 comments
Logic16 Teardown

 

In this episode Shahriar takes a look inside the “Logic”, “Logic16″ and USBee SX which were reviewed in the previous episode. The PCBs get a closeup inspection along with some insight into the design of these products. How do they compare? Well, you’ll have to watch the video to find out! Make sure to comment and join our Community Forum to discuss these products.

 

 

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Saleae Logic and Logic16 Product Review

May 31, 2011 Shahriar 5 comments
Logic16 from Saelae

 

As our first episode Shahriar will review two products from Saleae: “Logic” and the brand new “Logic16″. The video review also features USBee SX which is a direct competitor to Logic. Logic ($149) and Logic16 ($299) can be purchased directly from Saleae’s website or from one of their distributors.

Make sure you watch the next episode where we take these units apart to see what makes them tick!

 

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