In this episode Shahriar takes a close look at programming the popular NeoPixel RGB LEDs using a PIC microcontroller and C-language. A close-up of the NeoPixel (WS2812) LED is shown with attention to identifying various semiconductor elements inside the package. The principle operation of the LED is the described along with a detailed explanation of the pins and the one-wire communication protocol.
A simple evaluation board for the PIC18F4550 is used to drive a circular array of 60 NeoPixel LEDs from Adafruit. After presenting the difficulties of providing an accurate pulse-shape using the C-language, the measured waveform is shown on a Tektronix MDO4000B. Finally, the code for a circular color rotating pattern is presented and demoed. The code for the experiment can be downloaded here.
There is also equipment giveaway! A TPI Scope Plus 440 and a Tektronix TDS2232 are being given away at no charge! Please leave a comment on the video or on the website. You must be a resident of the USA to receive the giveaway. A winner will be chosen at a later date and notified via email.
In this episode, Shahriar upgrades an Agilent 53131A Universal Counter with the OPT-030 which extends its frequency range from 225MHz to 3GHz. The upgrade kit is a replica PCB intended to emulate the behavior of the original Agilent branded option.
The PCB is examined carefully with attention to microwave layout techniques along the signal path. The datasheet of all the parts are reviewed and the reverse-engineered block diagram of the PCB is presented. The expected behavior of the PCB is then measured in both small-signal and large-signal operation using an active 3GHz probe. The PCB is then installed inside the unit and the functionality of the instrument is verified within its specifications. All the documents presented in the video can be found here.
In this episode Shahriar repairs an Agilent 86120B Multi-Wavelength Meter. The instrument reports “E14 Data Acquisition Problem” which corresponds to a potential internal HeNe reference laser failure. After the instrument disassembly, the old HeNe laser is removed and its optical power is compared to that of a new laser. The measurements confirm that the old laser has significantly deteriorated in output light intensity. The new laser is fitted inside the unit and the error message is eliminated. The free-space optic portion of the instrument is revealed and the principle operation is reviewed. Various components of the Michelson Interferometer is examined.
To test the correct operation of the instrument, a single tone semiconductor laser is applied to the unit and the result is compared to a different wavelength meter. The concept behind the operation of a Fabry-Perot laser is also presented before the signal is applied to the wavelength meter.
In this episode Shahriar reviews and demos the second revision of the industry’s first Mixed Domain Oscilloscope from Tektronix. The MDO4000B series offers improved signal integrity and performance. The reviewed model is a MDO4104B-6 which offers 16-Channel Logic Analyzer, 4-Channel Oscilloscope with 1GHz of analog bandwidth as well a 6GHz Spectrum Analyzer with greater than 1GHz of instantaneous capture bandwidth with 65dB of dynamic range.
After an overview of the instrument’s interfaces and built quality, the block diagram and principle operation of the instrument is explained. The time-correlated digital, analog and RF capturing capability is described and its advantages for debugging complex mixed-domain systems is explored. Instrument probes, accessories and various modules are also presented.
The instrument is used to measure an ultra-pure single-tone signal at various frequencies for THD, SFDR and dynamic range measurements. For the main demonstration, a complete I/Q modulator system prototype is presented. The prototype includes a Maxim MAX2721 modulator, external PA, antenna diversity switch SW-277, digital control circuitry, power-grid DC-DC converters, external step attenuators, an Agilent E4342B synthesizer for LO generation and an Agilent N6020A arbitrary waveform generator for baseband signal generation. The Tektronix MDO is used to monitor RF, baseband, digital and power-supply analog waveforms. The system includes an array of problems including intermittent spurious tones, power supply dependent spectral noise, antenna switching glitches and 256-QAM constellation imperfections. The MDO is used to analyze, measure and solve all system problems. Tektronix SignalVu is used to analyze the system performance. As a final experiment, the MDO is used to demodulate a 1GHz bandwidth 32-QAM 500MS/s signal centered at a 3GHz carrier. The experiment documents can be downloaded here.
In this episode Shahriar demos the world’s fastest oscilloscope! The AgilentDSA-X 96204Q offers 160GS/s of conversion rate with a bandwidth of 62GHz on two dedicated ‘RealEdge’ channels. It can also provide 80GS/s conversion rate and 33GHz of bandwidth on four simultaneous channels. The unit demoed in this video is equipped with all available options and is valued at over 0.5 million US dollars. The block diagram of various sub-systems of the oscilloscope are presented and the principle operation of the instrument is explained. A 56Gb/s PRBS-15 signal is applied to the scope from a Centellax 2G2P5A (now Agilent N4975A) and the resulting data pattern is examined in real-time. Various scope functions are also presented as well as the capability to observer bit failures at baud-rate using this instrument.
As a second experiment, two 3.125Gb/s PRBS-7 data streams are simultaneously up-convered to 20GHz and 40GHz respectively by using a pair of MITEQ mm-wave DSB tripple balanced mixers and a pair of Avantek 20-40GHz YIG oscillators. The resulting two signals are combined by using a power-combiner and fed to the oscilloscope. The capability of the instrument to act as an ultra-broadband software-defined radio is demonstrated by recovering the two PRBS sequences simultaneously through DSP post processing. The block diagram of this setup can be downloaded from here.
I’d like to thank Mr. Neil Hoffman from Agilent for enabling this demo and Dr. Jeffery Lee for his help with the experiments.
This is "The Signal Path dot com"! An electrical engineering video blog for students, hobbyists and hackers. I do equipment reviews, teardowns, circuit design tutorials, testing procedures and more! Subscribe to my RSS, join the community forum and participate in the discussions.