Search results

Search Forums New Posts
  1. hevans1944

    Shadow signal

    I don't want to intrude too much on this fascinating discussion, but what exactly are you trying to accomplish with variable-frequency square or triangular pulses followed by so-called "shadow" waveforms? BTW, the two oscillators with ganged frequency controls are not coherent to each other...
  2. hevans1944

    Transformer/Coil

    Not true. It is exactly why we are here. It is called a conversation. Obvious to you only. Remember, you came to us seeking answers. If you don't like our responses, take your business elsewhere. We are more than happy to share our knowledge, but first we have to know how much you know. You...
  3. hevans1944

    Transformer problems

    Yes you could, if you were serious about maintaining authenticity of appearance. But what most hams did after about 1950 was to replace vacuum tube rectifiers with silicon diodes. They kept the vacuum tubes for RF power, but eventually changed to solid-state designs as high frequency...
  4. hevans1944

    Help rf linear amplifier 11Mhz

    Minicircuits.com has a variety of linear amplifiers you should investigate. Their ZHL-5W-1 seems appropriate for your requirements. See attached PDF file.
  5. hevans1944

    Transformer problems

    The power supply I built for my Novice amateur radio transmitter was constructed with two transformers salvaged from TV sets. I wired the primaries in parallel of course for 115 V AC line operation in the States, but IIRC the high voltage secondaries were wired in series to provide AC to a 5R4GY...
  6. hevans1944

    Transformer problems

    I would not recommend applying twice the rated primary voltage. You will likely saturate the core on the line peaks and overheat the transformer. Try purchasing two and connecting the primaries as well as the secondaries in series. You can also have a 240 V AC to 800 V AC center-tapped...
  7. hevans1944

    Fireflies blinking lights

    I am still learning about magnetic toroids... for amateur radio work. They come is all sorts of compositions and most do have an insulating, waterproof, conformal coating. The two main compositions are powdered iron and ferrite ceramics. I haven't bought any powdered iron toroids, which...
  8. hevans1944

    Thoughts on the Turing Test.....

    @Fish4Fun you bring up some interesting perspective on the "problem" of identifying machine artificial intelligence. One of the earliest science fiction short stories to explore the consequences of computer AI was Murray Leinster's "A Logic Named Joe" which I recommend to anyone interested in AI...
  9. hevans1944

    Fireflies blinking lights

    I like the idea of "transformer" coupling the power from a single wire wound about and through each "firefly" and then back to the source. Might want to consider using a small toroid core instead of a ferrite rod for more efficient magnetic coupling. Might get by with a single wire through the...
  10. hevans1944

    Designing a Time Delayed Relay

    Well, I have used a lot of line-powered equipment that omits any sort of fusing. In a few instances this has proven to be "penny wise but pound foolish" when something failed in a rather spectacular fashion. I have a current project in place now that uses an OEM open-frame linear-regulated DC...
  11. hevans1944

    Fireflies blinking lights

    Yes, IF you wanted a self-contained device powered perhaps by a 3V Li-ion coin cell, a cheap CdS or photoresistor would extend the battery lifetime to several months (probably) with a proper design. Do you have a favorite PIC in mind? I would like to get involved with those, now that I have more...
  12. hevans1944

    Fireflies blinking lights

    Fade up to full brightness, hold, fade out, wait a random interval, repeat. This definitely looks like a job for a PIC or small microcontroller. Power on wires is the way I would go. You can hook the power supply up to a light sensor so it only operates from dusk 'til dawn. No vampires...
  13. hevans1944

    Fireflies blinking lights

    "Random" delays can be accommodated by altering a timer variable in the main loop of each microcontroller. Most simply, a different timer variable would be selected for each microcontroller. After a few dozen cycles they should all be sufficiently "out of sync" to appear random to the casual...
  14. hevans1944

    Fireflies blinking lights

    A quick web search reveals that there are "blinking LEDs" available, as well as numerous circuits to make ordinary LEDs blink. IIRC, a firefly blink is a rapidly increasing pulse of light followed by a slower decay. Haven't actually studied any real fireflies lately to verify my recollection...
  15. hevans1944

    What can I make with two BIG transistors?

    Gee, these could be used to drive a really big Tesla coil... and I suppose an inverter for a 600 V DC solar array is also a good application, as would be a tig welder. It all depends on how adventuresome you are. Prices for these found on the web are about US$175, so your pair would set you back...
  16. hevans1944

    Hello all!

    This thread (Hello all!) in forum "Introductions" seems to have crossed to "Voltage Regulating Circuit Recommendations" in Forum "Circuit Help." This probably has nothing to do with Kansas or Oz.
  17. hevans1944

    Power supply noise.

    Could you make a sketch of the circuit you are currently using, take a photo of it and upload to the forum on your next post? It would help if you label the components (R1, R2, ... C1, C2 ... L1, L2 ... U1, U2, ... etc.) so we here on the forum can discuss and offer suggestions. A few years ago...
  18. hevans1944

    Designing a Time Delayed Relay

    @chopnhack : Great job, John! I recommend that Ian make this thread "sticky" for newbies, as well as for old pros, to see just what this forum is all about! From Day 1 on April 27, 2014 @chopnhack (who admitted he had very little experience in electronics) posted a clear description of what he...
  19. hevans1944

    Help me to find a "Novation Ableton Launchpad S"?

    Or how about a new one, here for 150 USD?
  20. hevans1944

    Need Help with auto switching Reverse Polarity Circuit

    I don't subscribe to homeopathic remedies, but there is some so-called alternative medicine that does appear to have some merit... at least to me. Colloidal silver, whether homemade or not, is probably harmless to the body, but there is no scientific "proof" it is effective at promoting health...
Top