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  1. K

    Linear talks

    Mixing up the pins can burn out the potentiometer element in some situations. This occasionally happens in the the breadboard trainers in our Physics' student lab. Lets say you're using the pot as a voltage divider across a power supply. The ends of the pot are pins #1(CCW) and #3 (CW). The...
  2. K

    Female Header

    No, they require a minimum size pin to make good contact. There is a gap in the internal female contact, unlike the white breadboards. Ken
  3. K

    Project: Speech controlled power supply and signal generator

    Have you Google'd: HM2007 circuit There are many pages about this circuit (kit). This could be directly interfaced to an MCU. You would then need to figure out how to come up with a power supply and function generator that can be controlled with the digital or D/A output of an MCU. Then spec...
  4. K

    Project: Speech controlled power supply and signal generator

    Then, maybe you have selected a project that is beyond a combination of your current level of education and ability. You may have to work up to something like that through more basic electronic and MCU projects. Ken
  5. K

    Project: Speech controlled power supply and signal generator

    I think you really have to understand the HM2007 operation completely before you try to pick an MCU. Ken
  6. K

    Project: Speech controlled power supply and signal generator

    OK, what data configuration do you need to send to an MCU? Ken
  7. K

    Project: Speech controlled power supply and signal generator

    When you asked what MCU, one of the spec's will be what interface configuration would it need from the Speech module....8 bit parallel binary?, 16 bit parallel binary?, serial?, SPI?, I2C?,...? Then you would need to know what inputs a power supply and signal generator would need, to spec the...
  8. K

    Project: Speech controlled power supply and signal generator

    Very important! > What are the outputs from the speech recognition module? It will say a lot about what you can do with the MCU and the rest of the design. Ken
  9. K

    Foxhole Radio tuning help. My first circuit!

    Variable capacitors don't go to 0pF. They go from some "maximum"value to some "minimum" value, but not to zero. Congratulations! Ken
  10. K

    Foxhole Radio tuning help. My first circuit!

    For a real trench radio, you can also make your own diode with a piece of graphite "pencil lead" and a "Blue Blade" razor blade. For the variable capacitor you can use two pieces of foil or sheet metal on opposite sides of an insulation sheet, like paper, plastic, or glass. Ken
  11. K

    Foxhole Radio tuning help. My first circuit!

    I thinks that's wrong. Intra-winding capacitance goes down with increased winding spacing. Same as increasing the spacing between capacitor plates decreases capacitance. http://d4magnetics.com/page7/page7.html For the "same" wire gauge, tightly spaces enamel wire would have a higher...
  12. K

    Need Help creating a timed buzzer (prop bomb)

    I didn't have a greeting card, but I did have a recording picture frame. http://www.radioshack.com/graphics/uc/rsk/Support/ProductManuals/6300977_PM_EN.pdf. The "play" button could be triggered by a transistor that is triggered by the timer's audio output. The "frame's" output could go to an...
  13. K

    Need Help creating a timed buzzer (prop bomb)

    I'm not sure at this point, but I think it could be done. I would use the microcontroller...because I have them. I may have to play around with the card recorder. Ken
  14. K

    Need Help creating a timed buzzer (prop bomb)

    The kitchen timer is just the timer portion. You would need a sound recording device like the microcontroller I recommended, or maybe the one out of a greeting card and amplified. Ken
  15. K

    Need Help creating a timed buzzer (prop bomb)

    A big speaker in a small brief case box would be impossible...but maybe a bunch of small speakers connected in series/parallel could get you enough volume. Direct drive the speaker array from a +12V supply with a MOSFET. The sound could be stored in a PICAXE 08M2 microcontroller and PWM drive...
  16. K

    Need Help creating a timed buzzer (prop bomb)

    My son played airsoft. Helped him work on a hand grenade. I'm still finding those darn little yellow plastic BBs around the shop...years later. If you're talking an audio boom, that means a big speaker and a big battery. How big a device do you envision? Ken
  17. K

    Does this button exist?

    What are you switching? How much...voltage?...current? How long does the ON-time need to be at push and release? What is the minimum push to release time? Ken
  18. K

    Unknown metallic boxes

    They are speakers used in the old Motorola Pageboy II pagers. I used to repair them...pagers...not speakers. ;) Sounded like this: Ken
  19. K

    Latching relay OFF on power lost

    Can you post a schematic of what you currently have? Might help in finding options. Ken
  20. K

    timer switch

    If accuracy is not critical, use an LM555 monostable driving a small 5V relay. Ken
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