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  1. hevans1944

    Just a quick check of my circuit

    Can you upload a keyboard schematic showing crystals with 3 or 4 pins? Sometimes a complete crystal-controlled oscillator module, with appropriate logic-level outputs and fast-transition edges, is used in lieu of a separate crystal with its required support circuitry. The oscillator module does...
  2. hevans1944

    Hi folks! I'm new here and don't understand JFETs

    You must have missed it, because it's not something you EVER forget! Although memorable for me, the quake I experienced was not large and it was short-lived. I don't recall that it was even the subject of discussion in the following days. Apparently earthquakes are a common occurrence in this...
  3. hevans1944

    New idea for oscillator

    Hey! Hey! Hey! I followed that link and it led to other links. And when I looked at all of them, nowhere did I find a 1000 x 1000 fat fist full of wires! So maybe this IS a crazy new idea! Well, crazy anyway. But wait! What if I want a 0.1 Hz oscillator? Does that require a tenth of a wire? Much...
  4. hevans1944

    Hi folks! I'm new here and don't understand JFETs

    Not sure what the "frequency" was, but I experienced a small earthquake on Okinawa sometime around 1958 or 1959 when Dad was stationed at Kadena AFB. I was outside when the ground under my feet began moving like it was alive. Very uncomfortable feeling. The entire "event" lasted only a few...
  5. hevans1944

    How are all our colleagues in Florida?

    Our Gulf beaches from Tampa south to Fr. Myers are contaminated with dead marine life. The smell is awful. The red tide organisms (a type of algae) produce neuro-toxins that are deadly to things living in the water, and from mild to severely irritating to humans breathing the air. One day a few...
  6. hevans1944

    9205(2)A multimeter

    In Cambodia $15.00 may be equivalent to a month's earnings. And this multimeter may be difficult to purchase online without a long wait for delivery to the OP's country. However, I doubt it can be economically repaired unless the components required can be obtained for free. Best to replace it...
  7. hevans1944

    Can I create and inexpensive wearable proximity warning device for the visually impaired?

    This approach is similar to how a "point cloud" 3D digitizer works, except stereo pairs are not used or created. The digitizer returns x,y,z co-ordinates of points on the surface of the scanned object. Importing this data into a parametric solid-model program, to allow eventual reproduction of...
  8. hevans1944

    How are all our colleagues in Florida?

    Some wind, some rain. Most of Hurricane Michael missed areas south of Tampa as it plowed through the Panhandle of Florida, causing extensive flooding and damage as it now heads for the Carolinas. It might have had the benefit of disrupting the Red Tide that plagued our southwestern beaches all...
  9. hevans1944

    Can I create and inexpensive wearable proximity warning device for the visually impaired?

    Sometime in the last century I was involved with the Defense Mapping Agency in St. Louis MO as an employee for a private contractor company that did highly classified work in support of the intelligence and reconnaissance community. One the DMA's missions (maybe it's only mission) is to provide...
  10. hevans1944

    Can I create and inexpensive wearable proximity warning device for the visually impaired?

    With the technology available today: a pair of CCD image sensors with pin-hole lenses, a really fast but inexpensive microcomputer, and a boatload of processor memory, it should be possible to develop a software real-time image processing solution, wearable and rechargeable battery powered. The...
  11. hevans1944

    Stabilizer for fridge, washing machine and Led TV

    Good one, Alec! From what I have been reading, some folks don't even pay for electricity there... they just patch into a circuit someone else is paying for. There are people in India whose profession is making these (illegal) connections.
  12. hevans1944

    Timer for laundry machine

    I have often wondered why so-called "white goods" are so expensive... washing machines, clothes dryers, cooking ranges, refrigerators, chest freezers... all are essentially painted or enameled sheet-steel enclosing some really basic (primitive, even) electrical and electro-mechanical parts...
  13. hevans1944

    Why does a LED tube light need a ballast?

    When we bought a house here in Florida it came equipped with fluorescent "curly bulbs" in every light fixture, except for two two-lamp, 4-foot, fixtures in the laundry room and garage. So we spent the first year here slowly replacing the curly bulbs with LED bulbs, not for improved efficiency...
  14. hevans1944

    Timer for laundry machine

    The biggest problem is going to be finding an inexpensive way to turn the motor on and off using a low-level logic signal. Optically isolated AC switches are common and easy to interface with. Control inputs vary from about 2 V DC on up, depending on how you want to control the optical isolator...
  15. hevans1944

    Change in resistance of electret microphone with sound

    Where did you read this? Please provide a link to the Internet reference because it is, at best, inaccurate. An electret microphone behaves as a variable capacitor with virtually infinite leakage resistance. Sound waves cause the capacitance of the electret element to change, not the electret...
  16. hevans1944

    Can someone identify this component?

    What?! You want high voltage to be present on the fence ALL the time rather than pulsed on and off? That's a recipe for disaster and perhaps death by electrocution. Don't even think about modifying a commercial fencer to make it "stay charged" all the time. Also, don't tug on Superman's cape...
  17. hevans1944

    Load, zener, series resistors currents

    Given the high frequency, 1 kHz, small load current, about 16 mA, and largeish capacitor, 100 μFd... calculate the voltage ripple from cycle-to-cycle assuming there is NO diode voltage drop. Is there a "significant" amount of ripple? If not, assume the capacitor charges to the 8 VDC peak of the...
  18. hevans1944

    Voltage Reduction

    Well good for you! These monster power supplies were quite popular about the middle of the previous century when digital electronics equipment required a multiplicity of voltages at moderately high currents. In Dayton, OH, the National Cash Register Corporation surplussed dozens of similar...
  19. hevans1944

    Voltage Reduction

    Sola is the brand name for a popular, line-operated, modular power supply. AFAIK the company has nothing to do with solar power. @Electromotive just needs to add a DC-to-DC buck converter to the Sola output to efficiently reduce the output from 24 VDC to 12 VDC. Tom, your selection depends on...
  20. hevans1944

    Convert 150 Ohm differential impedance to 100 Ohm differential impedance

    Where is the datasheet for the ADC? This looks like a pretty ambitious project for anyone "new to circuit design." What is the application? The MAXIM product was designed for use with a reverse-biased high-speed photo-diode, operating in transconductance mode (current-to-voltage converter)...
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