Svarichevsky Mikhail - RSS feed Svarichevsky Mikhail - RSS feed en-us Tue, 10 Jun 2006 04:00:00 GMT Wed, 22 Feb 17 13:39:59 +0300 120 10 <![CDATA[Time for decent SDR: Ettus N210 - 40Mhz of RF bandwidth]]>
Although it is surreal to see 50Mhz of spectrum in realtime (40Mhz bandwidth using UBX-40 - 10-6000MHz RF frontend) - it is only available on the host in 8-bit mode (it already requires 800Mbit/s - using otw_format=sc8 in device string). In 14-bit ADC mode we can "only" fit 25Mhz through gigabit Ethernet. But if you're ready to do custom processing on internal FPGA - one can do better.

Ethernet connection is really useful - now I can easily set it away from the PC, for example on a balcony - where I already have Ethernet cabling. Also it will not pickup any noise from the ground as Ethernet is isolated.

Tue, 14 Feb 17 03:56:35 +0300
<![CDATA[Time]]> ]]> Sat, 21 Jan 17 23:54:31 +0300 <![CDATA[Olympus 10x/0.3 WI - now with water immersion]]> previous post about my microscope I've mentioned that now there are no more cheap upgrades left. This microscope lens is first among more expensive ones : Olympus 10x/0.3 WI - with water immersion, was lucky to get it for 800$ on ebay.

Work with water immersion could allow to increase resolution (which is not used here - NA is only 0.3) and achieve slightly wider depth of focus for same NA - but (more importantly for me) it makes contamination of the specimen much less visible: dirt reflects/absorbs light very well on the surface to air and much less so in water due to much lower difference in refractive index.

Had to spent some time looking for proper containers for specimens which were flat enough (down to few microns). Finally, biological plastic Petri dishes worked well enough (glass ones were less flat but also usable). Very satisfied, fun lens :-)

First "production" photos here.

Sat, 21 Jan 17 19:20:18 +0300
<![CDATA[Flying over Minsk and Zurich]]> Minsk:


On the way back it was all covered with clouds:
Sat, 03 Dec 16 19:30:44 +0300
<![CDATA[Winter is coming : 1212 hours timelapse (50 days)]]> 50 hour timelapse - now it's time for 50 day timelapse (1212 hours). Starting from green leaves to snow. Shooting on Xiaomi Yi, 1 frame per 30 seconds, and then - 16x faster in ffmpeg via frame averaging. Total video speed is 28'800х realtime. Original video was ~80 minutes, 28.7Gb (50Mbit/sec bitrate).

Tue, 15 Nov 16 07:02:59 +0300
<![CDATA[Lighting fluorescent lamp on a bench (with 400V/1A power supply)]]>

Heating filaments from one side, ~100mA:

If we crank up current a bit (to 220мА) - heating alone is enough to excite mercury and get white fluorescence. This mode of operation is very dangerous to the lamp (this is exactly the way I fried filament on the other side):

Now lamp could be started from ~150V DC, discharge current is 100mA with ~42V voltage drop. DCDC power supply is not fast enough to support discharge due to negative resistance of the lamp, so ballast resistor is required. Minimal resistor for stable discharge appeared to be ~74Ω. With lamps of this type one can disable filament heating during discharge - this will improve efficiency and expand lifetime.

Without heating lamp could not be striked even by 400V DC, higher and higher filament current reduces striking voltage to 100-150V. But that could be further lowered by preheating both filaments and going AC using H bridge.]]>
Sun, 13 Nov 16 23:16:01 +0300
<![CDATA[59kV is no joke]]>
This is ~10kV ~2mA discharge:

Mandatory warning: Anything above 50V can kill you in "suitable" conditions. Achieving that at 1-60kV is much easier.

When arc gets orange - things get scary, metal electrodes start to melt and evaporate. ~15kV ~12mA, 180W in arc:

Droplets of molten copper on the wire:

In some positions of electrodes "on the side" there is a "thick" discharge rather than thin arc:

Here are my safety gloves - only rated for works up to 1000V, yet better than nothing. Random spark or arc will more likely go around the finger.

Inside the supply there are 4 transformers with HV diodes between them in HV heat-shrink tube. Everything is glued with some hot-melt white glue, looks not very reliable yet works just fine. On mains input they didn't omitted "unnecessary" common mode choke - that's a good sign.

When running for max voltage had to isolate terminals with glass vials in order to suppress electric noise around sharp electrode features:

Initially power supply was limited to 42kV for reliability reasons. Manufacturer gave instructions how to unlock full 60kV (that requires cutting 1 resistor inside).

And here is where priceless HV experience starts. HV voltage probe has a note saying that negative lead should be at ground potential. What does that mean? It has decent isolation only on "hot" terminal. If you leave HV supply floating - negative terminal will go somewhere around -30kV, and positive to around +30kV (60kV total), but weak isolation of ground terminal in HV probe cannot handle that and there will be a breakdown. But if you tie one of HV terminals to ground - probe is now ok, but hottest transformer inside supply is much easier to breakdown. This is exactly what happened.

Last voltage I've seen while testing for maximum voltage - -59kV, after cranking up voltage a bit further - I've heard the scariest thing one might hear - sound of arc inside power supply. Instinctively you expect it go bang and fly into pieces across the room :-) Luckily for me, only 1 last transformer got damaged gracefully.

How you tie HV terminal to ground - use neutral or protective earth terminal? Surely protective earth, you only have 50% chance of finding neutral in EU outlet :-) This is my "ground" tool:

After transformer breakdown it no longer holds more than 20kV. I guess experience was well worth it. To repair it I've ordered 4 spare transformers with HV diodes from the manufacturer. They actually surprised me by including spare parts with the supply - power transistors(20N60C3), spare microchip with markings removed and some passives.

PS: This is how how 60kV cable looks like:

Thu, 27 Oct 16 15:29:56 +0300
<![CDATA[Birthday PCB]]>

Sun, 23 Oct 16 21:17:32 +0300
<![CDATA[Growing mint and dandelion]]>

Also I've planted dandelion (taraxacum) - but it might take a while more until it flowers. It was unexpected that literally no one sells seeds of dandelion in Russia - had to get it from Great Britain.

I've also shoot timelapse video of plants growth : first part is 40'000x realtime (2 weeks in 28 seconds, there is no wind there - it's natural plant movement during growth), second part is 6'000x realtime (during daylight movement is much faster as sun moves around):
Tue, 18 Oct 16 11:07:25 +0300
<![CDATA[Long journey to a decent 50x/0.8 microscope lens]]> I wrote that my old used 50x/0.8 Carl Zeiss Jena microscope lens appeared to be worse than my original Chinese one. This did not stopped me - I bought more modern used Olympus UMPlanFL 50x/0.8 lens - and it appeared to be even worse : it was probably dropped once or twice, so it was completely misadjusted and it's resolution was several times worse than difraction limited. This lens was sucesfully returned to the seller.

Finally I got older Olympus MSPlan 50x/0.8 - and this one appeared to be nearly perfect. It took me 3 trials to get a decent 50x lens - yet another remainder that buying optical goods on ebay require some caution and that good optics visually does not differ at all from the terrible one...
See below quality comparison of all 4 lenses.

Olympus MSPlan 50x/0.8 (most recent one, keeper):

Chinese 100x/0.8 Planachromat (my old Chinese lens - too high magnification and slightly lower resolution):

Olympus UMPLanFL 50x/0.8 (resolution below any standards - likely dropped/misadjusted):

Carl Zeiss Jena 50x/0.8 Planachromat HD (vertical chromatic trail hints on misadjustment):

It looks like this lens closes the page of inexpensive upgrades of my microscope via ebay. Further upgrades are much more exotic, so that no one sells these on ebay (like 100x/1.45, 10x with water immersion or modern apochromatic lenses).]]>
Wed, 11 May 16 10:06:18 +0300