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 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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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
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:
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:
CD & DVD under microscopeI knew that there are tracks, but never was able to see them. My old pocket microscope was too weak.
Update: Photos remade with new camera. Also figured out how to make a good photo of DVD - I needed to brutally crack disk at half of it's thickness to directly access surface with written data.
Track interval is 1.6µm for CD and 0.74µm for DVD.
Photo of AMOLED display of Galaxy S4 mini and othersUpdate: Just realized that AMOLED means Active Matrix, so there should be transistors and some circuitry which I need to take a look at!
Suddenly my HTC One V died - blinked some random garbage on screen and became dark, discharging battery below 0%. I am not going to buy HTC again - I am far from happy with their policy of not updating Android on their 'small' phones.
As I am cool enough to buy non-top-of-the-line phones, I gone for Samsung Galaxy S4 mini. Why on earth all manufacturers have so much love for gigantic phones...
S4 mini has my beloved AMOLED display which promises longer battery life, 1.5Gb of ram is more than enough, 28nm Krait CPU (1.7Ghz, 1Mb of L2 cache) is perceivably faster than Scorpion (MSM8255 - 1.4Ghz, 45nm, 384kb L2 cache) and playing with NFC is fun. Finally it has LTE support - we already have LTE-capable networks here in Moscow - will be interesting to test it out. Also GLONASS is working
I decided to take microscope photos of displays of various devices I had at hands. Scale is the same on all photos:
Samsung Galaxy S4 mini - AMOLED:
MAKS 2013Weather was far from ideal, but in other days it was even worse. Hopefully they will shift MAKS 2015 earlier to the beginning of August.
There is no T-50 (PAK FA) on the video - I was too late for it by mere 15 minutes
Overclocking Arduino with liquid nitrogen cooling. 20⇒65.3Mhz @-196°C/-320°FBefore I start I guess I must answer 2 questions which would be asked inevitably:
1) Why? Because I can. To learn how electronics behave at cryogenic temperatures. And just curios how much juice you can squeeze out of AVR if you push hard enough This also produced some results relevant to desktop processors overclocking with liquid nitrogen cooling.
2) Why Arduino UNO (ATmega328P-based) while there are many faster microcontrollers? Just because it seems that Arduino is more popular among geeks and amateurs. For practical applications it is easier and cheaper to just use Cortex-M3/M4 based microcontrollers or FPGA (and I had these devboards too) instead of trying to overclock poor Arduino :-).
Overclocking microcontrollers with liquid nitrogen cooling promises to be harder, than overclocking desktop processors : there are no stability tests, no on-board programmable frequency generator (at least on AVR microcontrollers), no programmable supply voltage. Also, it appeared that a number of on-board components were failing - so I had to deal with them individually. Luckily for me all these problems were sorted out at the end.
ULN2003 - practical example of «reading» microchip schematicWe often receive comments that while our microchip photos are beautiful and interesting, it is completely unclear how integrated circuit implements basic elements and form larger circuit. Of course it is impossible to do a detailed review of an 1'000'000 transistor chip, so we've found simpler example: ULN2003 - array of Darlington transistors.
Despite it's simplicity this microchip is still widely used and mass manufactured. ULN2003 contains 21 resistors, 14 BJT transistors and 7 diodes. It is used to control relatively high load (up to 50V/0.5A) from microcontroller pin. Canonical use case - controlling segments of large 7-segment LED displays.
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