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  1. BobK

    Homemade High Amp Inverter Power Supply

    I don't think you mean inverter, perhaps you mean switch mode DC to DC converter? Bob
  2. BobK

    Homemade High Amp Inverter Power Supply

    200V at 40 A is 8000 Watts. Normal house wiring cannot handle this. How do you expect to power it? Bob
  3. BobK

    LM393 comparator...

    With a 10K pullup to 3.3V that is only 300uA of current, so I would think it would pull lower than the 0.45V that was observed. Bob
  4. BobK

    Capacitors Change impedance?

    Well, there is no capacitor in the circuit you describe, so of course it will flow in only one direction. If you have a resistor and capacitor in series with a power supply, and you raise the voltage the current into and out of the capacitor will be in one direction. If you then lower the...
  5. BobK

    LM393 comparator...

    For pretty much any logic family, 0.45V is low. Low does not mean ground, it means below the low logic threshold of whatever logic you are using. Bob
  6. BobK

    Capacitors Change impedance?

    A capacitor connected to a varying DC will have current that changes directions. Bob
  7. BobK

    Need help with voltage divider circuit calculations

    That is good advice if you only need to solve the equation once, but if you need to do it for multiple values, you need to keep all the variables as I did. Bob
  8. BobK

    Diode and Capacitor [Basic Questions]

    Yes, the diode will allow enough current to flow through the resistor to drop the other 4.3V, as a first approximation. Of course if the current required is too high, it something will burn out. If the current is very low, (say it is a 1 Meg resitstor) the current will be below the knee of the...
  9. BobK

    Very Simple Electronics Question

    Oh, okay, so not a speaker after all, but a siren module. Bob
  10. BobK

    Very Simple Electronics Question

    What makes you think connecting a 9V battery to a speaker will make a siren noise? Bob
  11. BobK

    Project understanding

    A crystal is normally used as part of an oscillator to set the PICs operationg frequency. In this clever little project, it has been replaced by a coil. The oscillator still operates, but now its frequency is dependent on how much metal is close to the coil, becuase that will change the...
  12. BobK

    Diode and Capacitor [Basic Questions]

    Did not notice that there is a resistor between the output of the Schmitt trigger and the anode of the diode? How does that effect the voltage on the anode? Bob
  13. BobK

    impedance of a constant current source

    I think he is using this circuit in place of the collector reistor in a common emitter amplifier stage. Agree that an LED is not the best voltage reference. Bob
  14. BobK

    Diode and Capacitor [Basic Questions]

    Current charges a capacitor. The voltage across it will change as it charges. A diode limits the forward voltage across it to something like 0.6V. In an astatable multivibrator circuit built from two bipolar NPN transitors, it is used to keep the voltage on the base from going far enough...
  15. BobK

    Need help with voltage divider circuit calculations

    Vout = R2 / (R1 + R2) * Vin Multiply both sides by (R1 + R2): Vout (R1 + R2) = R2 * Vin Multiply out the left side: Vout * R1 + Vout * R2 = R2 * Vin Subtract Vout * R2 from both sides: Vout * R1 = R2 * Vin - R2 * Vout factor out R2 on the right side: Vout * R1 = R2 *...
  16. BobK

    No voltage drop

    Floating means not connected to anything. Why are you trying to measure the voltage at a floating terminal? Or are you using the term incorrectly? Once again I ask, tell us exactly what you are doing to get this 1V measurement. Not answering questions is not a good way to get help. Bob
  17. BobK

    impedance of a constant current source

    Let's just say it's large. Bob
  18. BobK

    OP AMP comparison,

    The microchip low voltage rail-to-rail opamps are available in the standard 14 pin DIP quad versions. Bob
  19. BobK

    laser ablation of PCB resist

    So, the idea is the coat the board with resist and use a laser to remove the resist wherever you want the copper removed? Bob
  20. BobK

    Snowstopper

    I will be doing that in a couple of weeks. To go skiing. Go figure. Bob
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