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  1. hevans1944

    how to build programming logic?

    Learning how to program (computers) is much like learning how to teach a very young child... a two or three year old, for example. If the child is innately of superior intelligence, the learning goes quickly. But, unless you are working with a very sophisticated computer that has already been...
  2. hevans1944

    AC/DC Adapter Question

    Usual is a rather vague term in this context! It is usual for power supplies to run warm, and without forced air cooling this could be considered hot. As @AnalogKid noted in his post #3, this is a linear power supply. It will get warm during use. It probably has a small, inefficient...
  3. hevans1944

    Using Detuned AM/FM Radio as Spectrum Analyzer Input

    This sounds familiar... IIRC. :rolleyes: Spectrum analyzers (SAs) or, more generally, vector network analyzers (VNAs), are fascinating pieces of equipment. One of these days I hope to own a nice VNA to supplement the RigExpert antenna analyzer I use in my amateur radio (AC8NS) hobby. Gotta stay...
  4. hevans1944

    Optics, filters probably

    Hmmm. Maybe you can make a mechanically-scanned color TV camera with this set? Not sure what the cyan or aqua-colored filter would do in such an application though. These are pretty thick pieces of glass... could they be insertable band-pass filters for an optical spectrometer or photometer? I...
  5. hevans1944

    Little Electronics storage ideas

    What!? You want to store and sort your parts stash? Such optimism. I just put whatever part(s) I have recently acquired in whatever is convenient to store them... empty 35mm film canisters, empty diabetic blood-sugar test-strip canisters, Mason jars, Tupperware containers, cardboard boxes...
  6. hevans1944

    AC/DC Adapter Question

    Here is a Google search result that might help...
  7. hevans1944

    Using Detuned AM/FM Radio as Spectrum Analyzer Input

    Really? Here is a comprehensive "datasheet" describing the handheld Rhode & Schwarz FSH6 Spectrum Analyzer. Searching with Google, I couldn't find any information on "R&S FHS6's" that you claim to have. But, congratulations on having two of whatever it is that you DO have. If I were looking to...
  8. hevans1944

    using bjt amplifier to obtain a current higher than the maximum current an arduino can output

    Bye, bye, @abder! It appears you are one of our infamous drive-by posters who leaves when an immediate answer to their problem is not forthcoming. I say this because you have not responded to a dialog offered by @WHONOES and @Audioguru. Perhaps you were put off by @Harald Kapp's suggestion in...
  9. hevans1944

    Building a circuit to send current to a powered on, powered off valve

    Any sufficiently advanced technology is indistinguishable from magic-*. In this case, the magic is in the relay. Choose wisely, Grasshopper! More may be revealed. * "In 1962, in his book “Profiles of the Future: An Inquiry into the Limits of the Possible”, science fiction writer Arthur C...
  10. hevans1944

    need help electronic/relay problem phone horn

    You certainly can look for one, but without knowing how much voltage (presumably AC since the speaker must make a "ringing" sound) and how much current is available from the cell phone to operate it, what are you going to look for? Back in the day (I am talking the previous century, and very...
  11. hevans1944

    Any infos on µA circuits?

    Often, in the scientific research community, someone will try to duplicate or replicate the work of someone else, as described in a peer-reviewed paper or a description from some other means of publication. Often "sketches on the back of paper napkins" are all anyone has to work with. I once...
  12. hevans1944

    Connecting a 8 ohm buzzer with a 555 timer

    There is a lot wrong with the original article. The parts list specifies "1 x Small Rain Sensor" but provides semi-useless instructions on how to make one using interleaved aluminum strips, presumably aluminum foil, cut out and glued to a "Bakelite or Mica board." The picture shown on the...
  13. hevans1944

    Connecting a 8 ohm buzzer with a 555 timer

    Why would you think that? For the timing values given (Ra = 3.3kΩ, Rb = 68kΩ, C = 10 x 10-9 F), The Texas Instruments datasheet says the 555 timer, when enabled (RST high), will oscillate at roughly 1000 Hz according to this formula: freq = 1.44 / [(Ra+2Rb) C] Well, it oscillates briefly, how...
  14. hevans1944

    Connecting a 8 ohm buzzer with a 555 timer

    I am wondering, what is the purpose of C1 (22μF, 50V)? If the rain sensor becomes sufficiently conductive, because a rain-drop hits it, then Q2 (2N2222), will conduct through R3 (10kΩ), the base-emitter junction of Q1 (BC548), LED1, and R2 (330Ω). Thus, Q1 conducts and LED1 illuminates if the...
  15. hevans1944

    Alarm clock in LED

    ASAP translation: Aw Shucks Another Priority. Here at Electronics Point, the difficult we do right away; the impossible takes just a little while longer. If a project cannot be completed ASAP, it is placed on the back burner at a low priority. Of course, the original request for ASAP is never...
  16. hevans1944

    'Letraset' type dry transfers for PCB pads chemical etch resist

    Well, if you are still interested in dry-transfer letters and symbols, here is a company that will custom manufacture sheets for you. No idea how much this would cost, assuming you can provide appropriate camera-ready artwork. Back in the day (late 1960s) I used to use these transfers to apply...
  17. hevans1944

    Frankenstein's Components.

    I inherited from my grandfather an amazing power transformer with multiple low-voltage taps. I have no idea what its original purpose was, but at the time I was interested in what effect electricity would have on ordinary tap water. IIRC, I was maybe seven or eight years old at the time and...
  18. hevans1944

    Temperature Probe Testing

    Good point! Eliminate the mess of trying to add boiling water to already heated tap water, while at the same time trying to maintain an even temperature distribution while maneuvering the "digital scientific thermometer" to obtain a stable reading. I mentioned using a resistance heater rated...
  19. hevans1944

    Temperature Probe Testing

    @crutschow: I like your reasoned responses in this thread. Clearly, @enli does need some sort of battery-powered heater to maintain a constant "calibration" water temperature of either 140°F ±4°F or 170°F ±4°F, although not both temperatures at the same time. You could use two water baths, with...
  20. hevans1944

    Solar lead acid battery housing

    What you think you have found about lead-acid batteries is not in any way true. No battery does real well in cold environments for the simple reason that ALL chemical reactions slow down as their temperature decreases. While it is true that excessive temperature will have the detrimental effect...
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