Design Con 2015

Marian Stofka

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Dr.

Marian Stofka is with the Slovak University of Technology, Faculty of Electrical Engineering and Information Technology in Bratislava, Slovak Republic.


Marian Stofka

's contributions
  • 10.28.2014
  • Professor wants to change engineering education
  • "mistakes are tolerated and even encouraged" ... We should thoroughly specify these mistakes: If there goes about mathematics, there is no room to change arbitrarily its rules; many of which are 300 or more years old. Once you make an improper modification of the right-hand side of an equation so that it is no longer equal to the left-hand side, then any continuation is just wasting of time. In electronics, however, students really should be encouraged to make a "mistake-s", e.g. by loading the output of a fast amplifier - to see if it slows down or even starts to oscillate.
  • 09.01.2014
  • Optocoupler speed-up also reduces power consumption
  • ...the photo-transistor has an unmitigated Miller capacitance from collector to base.... - True, but you can beat the "unmitigated" also indirectly, by short temporary overshots (undershots) of the forward current of the LED within the optocoupler; as above. Also your true name can be evaluated indirectly - by clicking onto your acronym and then to some of your articles.
  • 09.01.2014
  • Optocoupler speed-up also reduces power consumption
  • If the top simplicity would be an aim, you could skip the circuitry at left-hand side of the above schematic in Fig. 1 with the exception of REL=82 Ohm; while connecting the left terminal of REL to VIN terminal. The factor of speed over power consumption would decrease, however. If you are still persuaded you are right; give specific data on comparable Avago circuit. By the way, the IC1 in Fig.1 is an Avago device.
  • 05.06.2014
  • Can you analyze this circuit?
  • Martin, if I were a teacher in the mentioned class, I had no problem to apologize to pupils and correct the drawing as you describe. Another possibility is to replace "10 A" by "20 A"; thus "12 A" notation can remain at R1 = 2 Ohm and Ix = 8 A. A teacher, who is not apt to apologize, could claim, that parallel with a lead from positive pole of battery to upper terminal of R1 there as an another identical lead, which is invisible, transparent (SnO2 or ITO type) or hidden; yet it carries another 10 A current; so the total supply current is 20 A.
  • 03.06.2014
  • Ohms per square
  • "even if the cross section isn't really square," - it should be stressed for young readers, that cross-section is meant here as slicing the resistor, or more precisely its resistive layer, by a plane planparallel to base of the resistor. The real SMD resistors resemble highly the above "perspective view" with the exceptions, that cyan "wires" are omitted and "Depth" within the above formula is the thickness of a resistive layer deposited atop the nonconductive body, usually alumina, of the resistor.
  • 03.05.2014
  • A blimp of LEDs
  • Weigh of the LEDs themselves can be estimated as 235,200x1gram=235.2 kg. Even more interesting is powering of these LEDs. If all LEDs were simultaneously operating @0.1A each (some 15% of LEDs are turned on at above picture), the installed power requirement could be 3Vx23,520A= roughly 70 kW. At left bottom corner of the picture some dark line can be discerned; is it a power cable?
  • 03.04.2014
  • 200 lm/W efficiency barrier smashed
  • I was eager to look at data of the first 200 lm/W LED commercially available. Inside the datasheet a maximum typical efficacy of 131 lm/W can be found for "Lime" LXZ1-PX01 type @ 500 mA. At 350 mA the efficacy can be expected mildly higher, as the efficacy-vs-current is a "little bit" concave curve; but scarcely it reaches 200 W/lm. A possible conclusion: April 1 is approaching fast...
  • 02.20.2014
  • Is Technology More Advanced than it Appears?
  • "What I get from real covert sources I do not talk about on the Internet" Dennis, I am far from scaring you, but now you seem to be really threatened. The only alleviation of your situation could be, if the "sources" were associated/identified with those services, mentioned earlier.
  • 02.20.2014
  • Is Technology More Advanced than it Appears?
  • Dennis, I start here, within this little linguistic corner. I am ready to discuss also rich amount of other topics, related to your article. But,... right after I posted my recent postings to it - my direct link to EDN become and remained inactive.... Is it a warning? BTW, aren't you afraid of attracting attention of secret services, when publishing articles as above? Now, back to little linguistic corner: German Fichte means "spruce", and not "pine". Pine needles of a spruce are shorter and of more vivid green color than those of a pine. Further, I am using this place in an attempt to put into order terminology of UFO as for term of "flying saucer", mentioned above. It should be renamed as "flying saucer-twin". You surely agree, that this kind of UFO looks like a stack of two identical saucers, where the upper one is up-side-down residing on the bottom one.
  • 02.20.2014
  • Is Technology More Advanced than it Appears?
  • I cannot resist a lure to translate into English surname of the author of the above article (maybe he won't get angry with me): Feucht in German language means "wet-related"; Feuchtigkeit = wetness.