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  1. hevans1944

    Radio Shack score

    <sigh> We have three Radio Shack stores still open in the Dayton OH area. The one closest to my house shut down without any notice and the inventory was apparently distributed to the remaining three stores. The next closest store is six or seven miles away in Kettering OH, but there are no...
  2. hevans1944

    I2C from scratch

    I don't think you are "overthinking" this. I will assume you already have a micro-controller, such as an Arduino Uno R3, that will support the I2S serial protocol in hardware, with appropriate software to serialize the data representing a row (or column, depending on wiring) of eight LEDs. Your...
  3. hevans1944

    Multiplexer

    Using the 74151 as a Boolean equation "solver" is a perversion of its original intent: to select one of eight data inputs and transfer that input to the Y output. Sure, you can hardwire the data inputs to binary constants to create any arbitrary Boolean function of three variables, duplicating...
  4. hevans1944

    Luxury and Intelligent Massage Chair Model #TL-601B

    You could also visit this web page and send Miss Fannie Chen, Sales Manager, an e-mail (scroll down the page to see how).:rolleyes:
  5. hevans1944

    Multiplexer

    Your circuit does not implement the Boolean equation Y = /CBA + CB/A + C/B/A + CBA, where the "/" prefix denotes complement (since I don't know how to put a bar on top of a letter). So, wherever there is a "/" prefix to a variable, substitute a 0 and where there is not a "/" prefix substitute a...
  6. hevans1944

    Multiplexer

    The 74151 will select one, and only one, of its D0, ... , D7 data inputs for presentation at the Y output on pin 5, based on the input-select bits A,B,C. This can be used to implement Boolean logic by connecting appropriate D0, ... , D7 inputs to either logic "1" (Vcc) or logic "0" (GND) levels...
  7. hevans1944

    Difference between SNR and HNR

    Does this help?
  8. hevans1944

    Help with PSU noise

    If you are going with battery-powered portable operation, why not just replace the switch-mode PSU with a nice quiet 24 V battery? That high-frequency ringing you see can be very difficult to remove. You could try an LC low-pass filter to knock down some of it, but beware of "sneak paths"...
  9. hevans1944

    I2C from scratch

    Looks like that device will drive eight LEDs, and you can put eight of them on a shared I2C bus for a total of sixty-four LEDs. How big is your LED matrix? Is it necessary that each LED is provided with its own latched driver?
  10. hevans1944

    printer power supply circuit help

    Perhaps you can purchase one here? Also, Google with "k 3654 nec" search string, coughed up these links, which may help narrow your search.
  11. hevans1944

    Changing The Current Direction inside the Peltier for temperature regulation

    Hard to say how I would do it, since I don't know the heat load on the cooled surface of your Peltier device, nor the heat pumping capability of the device. Is the controlled temperature considerably below ambient? One side of your Peltier device should be heat-sinked to ambient temperature...
  12. hevans1944

    Solar Panels for Hydrogen?

    You should have seen the hydrogen-jet nuclear powered rocket engine developed by NASA for a manned Mars mission back in the 1952 to 1972 period. Liquid hydrogen was stored on-board for use as reaction mass, not as fuel, and heated by a small nuclear reactor. The technology is well-developed and...
  13. hevans1944

    Solar Panels for Hydrogen?

    Hmmmm. Why not? Most of us here who propose ideas and/or attempt to solve problems have given it considerable thought. Else, this would be just another free-form blog. I think (my opinion only) you may have bought in to the "hydrogen economy" nonsense, and now are looking at possible...
  14. hevans1944

    passive matrix mixer - need help

    The only reason for the inverter is to make sure all signals retain their original phase, which would be important if later mixing occurs between inverted and non-inverted signals derived from the same source, such as a single musical instrument. It will not be apparent to the ear if this...
  15. hevans1944

    Solar Panels for Hydrogen?

    @cjdelphi: If you have enough solar power to make hydrogen in flight using electrolysis (an inefficient process), then you have enough solar power to run electric motors to turn propellers or ducted fans. Store any excess solar-generated electricity in supercapacitors while flying your...
  16. hevans1944

    passive matrix mixer - need help

    Your wiring looks okay. There should have been something at the output, unless you connected the output to a really low impedance load, like a headphone set with 8 or 16 ohms impedance. That will kill any signal trying to come through the 15 kΩ resistor connected to the wiper arm of the...
  17. hevans1944

    Changing The Current Direction inside the Peltier for temperature regulation

    I have a Peltier module that I was thinking of using to make a humidity sensor based on the dew point temperature. To do this requires mounting a smooth flat mirror on the cold side and then lowering the temperature until a light film of condensed moisture forms on the mirror. An IR LED reflects...
  18. hevans1944

    RAM Chips

    To accomplish the objectives of time-stamping events with one nanosecond resolution requires first of all a binary counter fast enough to count at a 1 GHz rate for one nanosecond resolution, and wide enough to store events for the longest period of time between the first event and the last...
  19. hevans1944

    voltage and current amplifier

    No, you are not right.
  20. hevans1944

    voltage and current amplifier

    Low power and high power are relative attributes of any signal. A high power RF signal for a broadcast radio or television station might be tens or hundreds of kilowatts. However, this would be considered a low power signal for a ground-penetrating or missile tracking radar system whose power...
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