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  1. hevans1944

    LM318N comparator circuit

    So, did your friend ever get the circuit to work?
  2. hevans1944

    Specification for my custom CPU

    For the last thirty years, it has always cost about US$2000 to build the best personal computer you need using current technology. Of course you can always spend more money, but it is unlikely you will need to. The extra cost will be for "bragging rights" more than for any improved and useful...
  3. hevans1944

    Specification for my custom CPU

    Why use a custom metal fabricator? PC cases are readily available over a wide range of prices, sizes, and bells and whistles (including LED illuminated interiors).
  4. hevans1944

    Digital calendar which flashes a LED when out of date range

    If you purchase the el-cheapo LCD with the embedded push-buttons, realize that those buttons are connected to resistive voltage dividers and all the switches go to the same output terminal. You read the voltage on this terminal with the Arduino (or, later, the PIC) analog-to-digital converter to...
  5. hevans1944

    Getting value of ADRESH out of a pic μcu?

    If you right-justify the A/D converter results by setting bit 7=1 in ADCON0, you can read all ten bits with this expression: AD_IN = ADRESL + (ADRESH * 256).
  6. hevans1944

    LM318N comparator circuit

    It is a reference voltage, but only after POWER rises from zero to the 7.5 V DC zener voltage. When that happens, the voltage on the inverting input (applied through R5) should remain more or less constant as POWER increases from +7.5 V DC toward the "switching" voltage of +13 V DC. But at the...
  7. hevans1944

    Digital calendar which flashes a LED when out of date range

    You are welcome! Please don't hesitate to ask if there is anything we can help you to do or understand. The codebender tutorial is a nice piece of work. The concept of a state machine with state transitions occurring as a result of events is an essential concept to real-time programming. Most...
  8. hevans1944

    LM318N comparator circuit

    This is a power Darlington good for eight amps or so. Why do you think it is a poor choice? What does the loudspeaker symbol connected from emitter of BD649 to GND represent? Is this the "buzzer"? What voltage and current does this "buzzer" require? Why is no means provided to limit the base...
  9. hevans1944

    LM318N comparator circuit

    Increase the values of R4 and R5 from 4.7 ohms to about 10 kΩ.
  10. hevans1944

    ONE CHANNEL REMOTE TO BELL WHICH PULSES WANT IT TO RING

    Isn't that what you requested in your original post?
  11. hevans1944

    Sound activated alarm

    It is possible to do that... and more. Voice recognition software is readily available for installation on personal computers such as lap-tops and tablets. You could add a USB relay controller to ring bells, light lamps, turn on a coffee maker... whatever you wish to control that operates with...
  12. hevans1944

    8-Pin Development Board

    Well, maybe. But the code you wrote seems simple enough, although perhaps with some syntax errors... I don't see a main program loop, and the curly brackets "{ ... }" do not appear to be paired correctly... a left curly bracket is missing. And the whole code snippet appears to be a subroutine...
  13. hevans1944

    3 phase transformer

    Thanks, Claude! Now I gotta go back and study what I must have missed in my power class. About the only thing I remember from that course was the concept of a constant amplitude rotating magnetic field created by three-phase excitation.
  14. hevans1944

    8-Pin Development Board

    Why are you left-shifting ADRESH by eight bit positions before adding it to ADRESL? The two MSBs of ADRESL contain the LSBs of the result since ADFM = 0. Shouldn't you right-shift ADRESL by six bit positions and then concatenate it to ADRESH? Excuse me if my questions doesn't make sense... I...
  15. hevans1944

    3 phase transformer

    Gee, I must have missed something... are you saying that if there is an unbalanced load on a wye distribution there is no current in the neutral?
  16. hevans1944

    8-Pin Development Board

    Indeed it is. This particular ADC uses ten successive approximations to arrive at a 10-bit result. Details of how that is done are not revealed in the Microchip datasheet. Typically during each conversion the input voltage, stored on a sampling capacitor, is compared with a binary-attenuated...
  17. hevans1944

    Need help to understand the amplifiers circuit

    I think it was probably an oversight in proof-reading the artwork before the paper was submitted and subsequently published after the conference you cited. This happens more often than you might think with this type of submission. Even peer-reviewed papers can have mistakes of omission or...
  18. hevans1944

    Need help to understand the amplifiers circuit

    Who knows what the "intent of the original design" was? Why all the resistors in series with the non-inverting inputs of six op-amps? Assuming "ideal" op-amps, these resistors serve no purpose since no current flows through them.
  19. hevans1944

    8-Pin Development Board

    I wasn't impressed with his delivery. Of course there was no math involved in this introductory video since it appeared he was trying to lure in a totally clueless audience. But to talk about short circuits in the manner he did was totally wrong. He implied that the wire somehow "sucked in" all...
  20. hevans1944

    8-Pin Development Board

    I read the thread but saw no sign of Ratch. Steve and Laplace were mostly involved. Did you finish that course? I think I will leave those off of my board and depend on the jumpers for "isolation" instead when I program the PIC. What kind of Schottky diode did you happen to have on hand to use...
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