Few words about me:From very childhood I loved computers, electronics, lasers, sulfuric acid and liquid nitrogen. I always wanted to be making microchips, UAVs and see nuclear explosion.
Now I am doing software engineering and in the spare time - some microelectronics and physics/chemistry experiments.
I live and work in Russia, Moscow.
My precious... ADCReceived few interesting chips from ebay for experiments and decapsulation...
Finally can play with fast ADC (16-bit 10MSPS, 14-bit 190 and 400MSPS), DAC.
It's hard to run ADS5474 at 400MSPS for fun, so it goes straight to acid
But with EPM7128 I made a mistake : I recalled that MAX7000 is the last Altera CPLD with 5V IO. But these specific chips appeared to be 3.3V ones (postfix A-3.3V, B-2.5B. 5V ones has postfix S or none)
February 18, 2015
PCB cross sectionEver seen PCB cross section? Total thickness is ~1.5mm, you can even see how glass fibers are interleaved.
January 22, 2015
Temperature stability of AirSpy SDR receiverRecently I got AirSpy SDR-receiver : it has 20Mhz/12bit ADC comparing to 2.4Mhz/8-bit one in RTL2832-based devices. Capture bandwidth is 9Mhz. Also, it uses TCXO with 1.5ppm frequency error spec. In this article I focus on it's frequency error vs temperature. More detailed review of AirSpy will follow in the nearest days...
BTW, for the first time in human history we have blueberry-cooled electronics:
Here are frequency errors. I was measuring 35-th harmonic of FE-5680A rubidium frequency standard generating 2^23 Hz, i.e. ideal frequency should have been 8192*1024*35=293'601'280 Hz.
|Hardware||Quartz (E4000+RTL2832)||AirSpy TCXO|
|After warm-up||293'627'555 Hz +89.49ppm||293'601'318 Hz +0.129ppm|
|Tcase ~0C||293'626'824 Hz +87.00ppm||293'601'185 Hz -0.324ppm|
|Tcase ~60С||293'628'227 Hz +91.78ppm||293'601'386 Hz +0.361ppm|
I didn't make it to amateur astronomy (this time)Recently I've bought telescope optical tube assembly - Levenhuk 200mm F4 carbon - there was nothing else in this class left in stock in Moscow, all sold out. But, as one could expect, chances to get decent Chinese F4 parabolic mirror are slim...
Brief test of DPSS laser partsFinally got some time to play with neodymium solid state lasers : ordered 2W IR 808nm laser for pumping and few glued crystal assemblies of YVO4:Nd+KTP (size 0.8*1.3*2.5мм). Unfortunately supplier made a mistake and sent 400mW IR laser instead of 2W one and promised to send the replacement. Meanwhile I decided to run few tests on the table with this first laser.
After focusing IR beam on the crystal generation immediately started as well as second harmonic generation - nice green spot appeared on the targer:
Globular cluster M1562 minutes exposure on T24 telescope from iTelescope.net (61cm aperture).
50 minutes for luminosity, and 4 minutes each for RGB with 2x2 binning. Apparently, color shots needed more time to lower noise.
The brightest starts in the cluster have magnitude of 12.6, and that super-bright star at the top-right part of the photo has magnitude 7.6 (which is twice weaker than we can see with our eye in perfect conditions). There are more than 100'000 stars in this cluster.
November 15, 2014
ZnSe lenses for CO2 laser: plano-convex vs convexo-concaveSome time ago I've bought CO2 laser engraver from China. It had lots of issues, including bad lens, which supplier had to replace. I've chosen 102mm replacement lens that time. A month ago I noticed that price of 20mm ZnSe lenses on ebay dropped to 15$, so I ordered more suitable lens for my engraver with 51mm focal length. When it arrived I was pleased with quality of edges and coating, but was surprised to see that it is an convexo-concave lens instead of usual plano-convex type.
On the left - first bad lens, on the right - replacement sent by supplier and in the middle - this new one.
Is there any practical difference between plano-convex and convexo-concave lenses for CO2 laser focusing? Also, which way one should mount it? Let's try to figure it out...