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  1. AnalogKid

    Power supply

    5 A at each output voltage? That's 225 W output power. ak
  2. AnalogKid

    Please explain circuit

    Some counters are shown with D flipflops internally, and some are shown with JK flipflops. These are just variations on a theme, and both require some form of feedback to toggle with each clock edge. With JK's it is internal. Often it is shown explicitly with D flipflops. ak
  3. AnalogKid

    Please explain circuit

    or a "logic 1", yes. ak
  4. AnalogKid

    Please explain circuit

    1. All Johnson counters are variations of a ring counter, and all ring counters are shift registers: https://en.wikipedia.org/wiki/Ring_counter#Johnson_counter 2. If you look at the CD4017 internal schematic, you will see that there is no feedback from each stage -Q output back to its D...
  5. AnalogKid

    Please explain circuit

    When the chip powers up or is reset, it is in the output 0 state. Pin 3 is high. Also, internally the 4017 is a shift register, not a counter (synchronous or non). ak
  6. AnalogKid

    Transistor for supplying ground, I think mine are way overkill

    How about a schematic so we can evaluate your question with some information? ak
  7. AnalogKid

    Switching Regulator

    Your two output power levels are 0.5 W and 0.33 W. While switching regulators certainly are possible at these power levels, a reasonable question is why go to all that trouble? Starting with a 20 V input, two linear regulators would dissipate 1.5 W and 1.67 W. Those are enough to require...
  8. AnalogKid

    Buck converter help

    With one resistor, one zener diode, and one power transistor (with a 150 V or higher rating) you can make a "power zener" circuit, basically a low-precision pre-regulator, that limits the voltage available to the buck converter. ak
  9. AnalogKid

    Buck converter help

    Ohm's Law defines that the voltage drop across a resistance depends on the current through it, so selecting the resistor value and power depend on the current being drawn by the converter, and that depends on the output current. As the battery charges up, the converter output current will...
  10. AnalogKid

    Newbie Project

    Your basic premise about sensing printer commands on the Ethernet cable almost certainly will not work without a significant programming effort. The "sniffer" mentioned above is a real thing, but not a beginner's project. There is constant Ethernet traffic going to the printer, and it is the...
  11. AnalogKid

    Need design help

    Once the unit is running, is there any time when the magnets are off, or is it always one polarity or the other? ak
  12. AnalogKid

    Need design help

    In round numbers, here is how this goes. If all 4 magnets are always switched together, then you need only one reversible power stage. That is called an H-bridge, or full H-bridge driver. With a single power system, like +12 V only, it can place almost 12 V across the coils in either...
  13. AnalogKid

    Switching leds

    The trick I described in post #14 for TR2 is the same thing being done by TR1, D7, and D8, and the opto. ak
  14. AnalogKid

    How do constant current loads work and how to make one

    There are several ways to make a constant current circuit, and searching for the term 'constant current schematic' will return many schematics. One way is to monitor the voltage across a resistor, and use an opamp to automatically adjust the conduction of a transistor such that the voltage is a...
  15. AnalogKid

    Switching leds

    Because R15 is on the high side of LR1, you're in luck. Add a second LED and a 1N4148 diode in series, connected from LR1 anode (the low end of R15) to GND. This string is in parallel with LR1 and TR2. When TR2 is off, R15 supplies current through the new LED and diode. When TR2 is on, the...
  16. AnalogKid

    Trying to make a transistor cancel another transistor

    But *we* don't know that. And it's not actually a complete view, is it? Are there any other circuit components or connections that are not on the drawing you posted? ak
  17. AnalogKid

    LEDs in parallel don't consume sum of individual currents??

    If you don't have individual current limiting resistors for each LED, your results are exactly correct. ak
  18. AnalogKid

    IC Chip question.

    The legs are not at 90 degrees on thru-hole DIP packages so that automatic insertion machines can grip them. There is variation among manufacturers as to how far out the pins are spread, but it always is greater than 90 degrees. The robot grips the chip, squeezes the pins to exactly 90...
  19. AnalogKid

    Vintage doorbell issues

    Don't think so. Some capacitors can dry out over tim, significantly reducing the capacitance value. But I've never seen a resistor disintegrate away due to nothing but age, and I've been inside some ooooold gear. ak
  20. AnalogKid

    help connecting 555 timer

    Whether distributed (post #10) or concentrated into 8-stage chips (post #12), I think the shift register approach is far better than 2,688 R-C timers. ak
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