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  1. hevans1944

    Need help with microcontroller project

    @Nbeagle and @willsonwanda: Mit enuf mikros ve cud rule de verld! Oh, wait... it's already happening.
  2. hevans1944

    a transistor is a variable resistor

    A thermistor is a current-controlled variable resistor: you send current through a thermistor and it gets hot and its resistance either increases or decreases. Any resistor whose resistance is a function of its temperature can also be considered a current-controlled variable resistor. And...
  3. hevans1944

    Short pulse output

    Yeah, me too! In early 1970s I was tasked with designing a controller for a raster-scanned X-Y positioning stage. This was part of a new laser window-test facility that we had been asked to spin up for the Air Force. I didn't know it at the time, but this was the beginning of our involvement in...
  4. hevans1944

    Short pulse output

    @danadak is absolutely right: integrated circuit processors are not sledge hammers, and they are really "dirt cheap" solutions to timing longish periods that in the previous century (circa 1970 or earlier) would have had to have been an analog circuit. Way back then, you could have cobbled...
  5. hevans1944

    Triac control system for soft start

    Well, being "retired" (with a tiny income from Social Security and a small annuity from TIAA-CREF), I have plenty of time on my hands. So, I thought I would give it a go on my iPhone. BIG mistake! I have run into the same problem in trying to type username and password (and other text) for apps...
  6. hevans1944

    Triac control system for soft start

    I’m typing on my iPhone in a forum for the first time… what a PITA this is!
  7. hevans1944

    How do I build this ultrasound device ?

    I skimmed through this paper and found it fascinating that a $10,000+ commercial ultrasound device could be effectively implemented with less than a few hundred dollars. The paper is well-written and effectively demonstrates how to do it. I was astonished by how well balanced and detailed the...
  8. hevans1944

    matched impedance question

    Guess that means neither you nor Keith have any "Golden Ears." Well, fer sure Keith doesn't. Hmmm. Sorry for hi-jacking this thread (see post #11). We are a long way from determining how to find out if the refrigerator light goes out when the refrigerator door is closed! My favorite way to do...
  9. hevans1944

    Triac control system for soft start

    Thanks for finding those two app notes, @Minder! Unfortunately, AN-3006 has a schematic that shows exactly how to implement line-synchronized phase control in analog fashion. All that is missing is the automatic, variable, time delay needed for a "soft-start". application. I didn't think we were...
  10. hevans1944

    Triac control system for soft start

    TRIACs are semiconductor switches. As such, they have ZERO current-limiting ability and are not serious candidates for "soft-start" start-up circuits without sophisticated trigger circuits. To do this properly requires timing the trigger pulse to be a variable interval from the first...
  11. hevans1944

    matched impedance question

    There is a LOT of misinformation, not to mention outright lies, concerning connectors and their associated wiring. The RCA connector is a coaxial-style connector, similar for example to a BNC-type connector. The BNC is impedance-controlled by its manufacturing design. The RCA is simply a...
  12. hevans1944

    passive gate chain amplifier

    I cannot find ANY "gates" on the posted schematic sketch. Also, how can any signal at all survive being applied through a one pF capacitor whose other terminal is connected to a power supply (A+ and B+) and to the A- supply through a one ohm resistor? IF there are "gates" somewhere, how fast and...
  13. hevans1944

    matched impedance question

    Backwards? All a reed switch (or ANY switch) does is present an open or a closed circuit. How this is interpreted by whatever electronic circuit uses the switch has nothing to do with "forwards" or "backwards" in how it works. That is up the the interpretation of the designer. So, yeah, a closed...
  14. hevans1944

    Synchro motors for wind direction indicator

    The chimney-mounted transmitting end of the weather vane display is potentially much more complicated than the receiving end, which is why I suggest designing the compass-rose display first. Generating ASCII character strings used to be quite simple when almost all PCs had one or more serial...
  15. hevans1944

    Synchro motors for wind direction indicator

    I see two options for producing an "analog appearing" display: (1) an LCD flat-screen display that simulates (visually) a needle pointer and a compass rose and (2) a mechanical needle pointer that revolves around the center of a printed compass rose. The problem with (1) is writing the software...
  16. hevans1944

    diagnostic port on smartkegger control board.

    Well, clues are nice to have... it appears that @roughshawd is quite literally a homebrew beer aficionado who wants to brew his beer at a controlled temperature below normal ambient temperatures... a cold lager process. I can remember my father making "homebrew" beer in the detached garage of a...
  17. hevans1944

    Synchro motors for wind direction indicator

    The article you referenced has a pretty good explanation of how a self-synchronous motor, a selsyn (or more specifically, a pair of them), works. These rotary shaft devices have three stator-wire connections common to both selsyns and a pair of rotor-wire connections, also common to both...
  18. hevans1944

    diagnostic port on smartkegger control board.

    IF @roughshawd knows as much about refrigeration as he does about electronics, I have a suggestion: Remove ALL the circuit boards and the control panel. What remains will be a basic refrigeration system. Try doing a DIY project to get it running to suit your application. You will need some...
  19. hevans1944

    Lava lamp

    That may not be possible. There is some intellectual property (IP) involved in knowing which microcontroller was used, and that is why a lot of Asian vendors scrape off or otherwise obliterate any identification that would allow someone else to easily "clone" their product. That's not to say...
  20. hevans1944

    Lava lamp

    There are a lot of members here who can help, but some more information would be nice. I did a Google search for "lava lamp with color-changing leds" and the results were a lot of inexpensive lava lamps. So it may not be economically sane to try to reverse-engineer your LED controller. OTOH...
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