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.
Fake audiophile opamps: OPA627 (AD744?!)Walking around ebay I noticed insanely cheap OPA627's. It's rather old, popular and high-quality opamps, often used in audiophile gear. Manufacturer (Texas Instruments / Burr Brown) sells them 16-80$ each (depending on package & options) while on ebay it's cost was 2.7$, shipping included.
Obviously, something fishy was going on. I ordered one, and for comparison - older one in metal can package, apparently desoldered from some equipment. Let's see if there is any difference.
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April 9, 2014
Fireworks in MoscowCelebrating reunion of Crimea with Russia. Same happened in Sevastopol and Simferopol - major cities of Crimea.
March 22, 2014
My HeNe lasersRecently I won HeNe laser tube on EBay, and seller from Germany surprisingly sent me 2 lasers instead of 1 :-) One is slightly newer (~2000), I even managed to find datasheet on manufacturer's website, another is older. Also I bought HV power supply - 2100-2900V, 6.5mA and 8000V during ignition. But the main issue for me was high-voltage ballast resistor - it is needed due to "negative resistance" of gas dischange, constant current power supply might not react fast enough. I had no any HV resistors, so decided to try 2512-SMD parts: they are rated for 500V voltage and 1W heat dissipation - so I will have to use them quite out of spec.
Voltage drop across 200 kOhm resistor for 3mA current is about 600V, so it did not brake down even for mere 2 resistors in series, but heat dissipation was so high (~1.8W on small board without radiator) that resistors were floating in molten solder. Obviously, It was impossible to add radiator on my protoboard I increased number of resistors to 6 and reduced total resistance down to 150 kOhm - this allowed for prolonged laser operation without resistor overheating. Now I see that i probably used too high ballast resistor value - even 75kOhm would work just fine according to datasheet. FYI documentation also suggest to place ballast resistor as close as possible to anode of the laser for stable operation.
I believe ballast resistors for CO2 lasers could be done the same way - but number of resistors must be like 10-30 times higher, and obviously on a single-sided board. One should remember that maximum heat dissipation for 2512 resistors is around 1W and temperature of whole ballast board should be monitored.
First laser started generating from 3.2mA (nominal current from datasheet - 6.5mA), second from ~4mA. I was measuring current using usual multimeter in the cathode wire - luckily it did not get fried during ignition
FTDI FT232RL: real vs fakeFor quite some time when you buy FTDI FT232RL chips from shady suppliers you have a good chance of getting mysteriously buggy chip which only works with drivers 2.08.14 or earlier. We've got a pair of such FTDI FT232RL chips - one genuine and one fake and decided to check if there is an internal difference between them. On the following photo - left one is genuine, right one is fake. One can notice difference in marking - on genuine chip it's laser engraved while on buggy it is printed (although this is not a universal distinguishing factor for other chips).
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February 19, 2014
Precision clock: rubidium atomic clock and Russian DOCXORecently I bought on ebay rubidium atomic reference clock for my precision time experimets (time drift per year under 50ms) and also double-ovenized 10Mhz quartz cristal oscillator from the same supplier (just for comparison, it was cheap as dirt).
After I received them - was really surpried that DOCXO is made in Russia, Saint Petersburg by Morion company. So this DOCXO made a full trip around the world - from Russia to China and back
February 5, 2014
Supernova explosion in M82 galaxyJust made a photo of supernova in M82 galaxy which exploded yesterday*. If things would go well, it will be getting brighter and brighter in the following 10 days or so.
0.5m telescope aperture with 3 minutes exposure:
▶ And this is how it looked before explosion:
January 23, 2014
M1 - Crab NebulaMade a photo of Crab Nebula via "couch telescope" iTelescope T7.
10 minutes for each channel, Ha (red channel), Sii (blue), Oiii (green). I.e. different colors - are different chemical elements (hydrogen, sulfur, oxygen) generated during nova explosion. We are looking here at the process of creation of the new world :–)
BTW Explosion of this nova was first observed just 959 years ago. It is even possible to see changes in Crab Nebula over the years.
Same without filters:
November 23, 2013