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.
World cheapest FPV "duct tape" quadcopter :-)
Ingredients: 33$ micro quad copter + 20$ chineese "HD" camera + 0.01$ duct tape. :-)
Camera weight was almost the same as quad copter, so it was very hard to take-off.
June 8, 2014
Flying Flight Design CTLSThis weekend I was flying on Flight Design CTLS. This is fully composite 2-seat small airplane, empty weight is just 326kg. This airplane costs about 200k euro, 1 hour of rental in the air club is ~200$. According to our approximate calculations it eats about 7 liters of gasoline (AI-95) per 100km of flight, some actually use it to travel across Russia.
On the video takeoff is at 3:45 , I am in control at 8:45 and landing at 11:45.
Among others flying same day my impression was the most neutral, apparently I am not going to be adrenaline addict. That was extremely interesting, but that's it. My interest was completely fulfilled.
I finally figured out that ailerons are much more useful than rudder. With ailerons you utilize maximum aerodynamic quality of the wings when changing direction of flight, while with rudder only fuselage is working, so you have aerodynamic quality of only 2-3 - this means you are loosing much more energy for the same rotation. It always felt unnatural that RC airplanes tend to use rudders for rotation, not ailerons.
Fake audiophile opamps: OPA627 (AD744?!)Walking around ebay I noticed insanely cheap OPA627's. It's rather old, popular and high-quality opamps, often used in audiophile gear. Manufacturer (Texas Instruments / Burr Brown) sells them 16-80$ 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
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