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  1. hevans1944

    How To Annoy Those Helping You Out

    Well, it IS in the Off Topic Members Lounge... I doubt any of us took @donkey's original post too seriously, although I do share his general sentiments. Why can't "they" tell us what "they" want to DO instead of offering up half-baked solutions and expecting us to fix it?
  2. hevans1944

    Choose Software or Hardware in electronics ??

    There was lots of software in the 70s and 80s. This is when the microcomputer revolution began. I know this because I was knee deep in it. Both electronics hardware and software development have kept pace with each other. I know of no software that can be executed without hardware. And I know of...
  3. hevans1944

    Touch switch for heating element

    There are basically two ways to control line power to a heater load: phase control or duty cycle. Phase control is a form of duty-cycle control applied to conduction in a triac over a complete AC cycle. You delay the trigger applied to the triac during each half-cycle to control its conduction...
  4. hevans1944

    How To Annoy Those Helping You Out

    Since the diodes were damaged from heat removing them, you should carefully dip them in a fast-drying red colored varnish and deposit them in the trash. That way, if they should ever find their way back onto your work bench, you can immediately dispose of them again, saving hours of frustration...
  5. hevans1944

    Simple theremin 555 timer

    Just glanced at your link. Looks like the real deal there. Simple RF circuits, easily available parts, and your choice of construction techniques ranging from full-blown etched PCB to "dead bug" and Manhattan style construction. Pretty good resource! Thank you.
  6. hevans1944

    Op Amp Circuit Noise

    Your equation describes what the 1/f noise is as a function of pore dimensions and bulk conductivity, but it doesn't explain how this noise originates. 1/f noise has been a bug-a-boo of electronics since before I was born, rearing its ugly head with thermionic electron devices (vacuum tubes) and...
  7. hevans1944

    Simple theremin 555 timer

    You are misguided on how a Theremin works. The two "antennas" of a theremin are part of two radio-frequency tuned circuits connected to the "tone" antenna and the "volume" antenna. Moving your hands close to these antennas changes the frequency of the RF oscillations by varying the capacitance...
  8. hevans1944

    Help identifying antenna jack

    Enjoy it while you still can. My cable service provider (Internet and Basic TV) recently sent me a "descrambler" box to go between my TV antenna input and the cable service. Seems that too many folks in this area are somehow getting a "free ride" off the cable plant, so Time Warner Cable is...
  9. hevans1944

    Op Amp Circuit Noise

    Very interesting way to create a nanometer sized fluid channel in a silicon nitride thin membrane. I assume you will use the Axopatch 200B to track the DNA strands as they make their way through the hole. Is it your intent to make just one hole per membrane, or is there a goal to make an array...
  10. hevans1944

    Op Amp Circuit Noise

    Would it also generate defects in or near the surface of an un-doped, semi-insulating, gallium arsenide wafer, selectively, through a photo lithographic mask? There is a device, called a GaAs PCSS (Photo-Conductive Semiconductor Switch) that can be fabricated by implanting oxygen ions in narrow...
  11. hevans1944

    Confusing results from voltage amplifier circuit

    Use a CD4050 logic-level shifter/buffer. Datasheet here.
  12. hevans1944

    Electromagnet with strength controlled by photoresistor

    Well, you have shown it can be done on a small scale. As you noted, just gotta get the control of the magnetic field placement to be little bit finer and more precise. On a similar note, a few years ago (well, maybe more than a few) I was trying to copy a contour on a piece of molding and...
  13. hevans1944

    Op Amp Circuit Noise

    Glad you got it working! I edited my original post to correct some arithmetical errors in the calculations, so you might want to go back and re-read it. The gist of it hasn't changed however. Lower the resistor values to lower Johnson noise, by-pass the power supply rails. Can you give us some...
  14. hevans1944

    Wi-Fi IoT using RF backscatter

    I haven't done a patent search to see what the authors think is patentable by exploiting basic physics. Probably the software they ginned up is patentable, but who knows what you can slip past a patent examiner these days? Wish I had the resources to pursue this. Oh, well, near-field...
  15. hevans1944

    Electromagnet with strength controlled by photoresistor

    Wow! You didn't tell us this was ART! What a wunnerful display of imagination! Kudos to you! This reminds me of a (obviously) CGI display of an interactive topographic map, now common in recent motion pictures, but that I saw most recently while watching an old DVD of X-Men a few nights ago...
  16. hevans1944

    Wi-Fi IoT using RF backscatter

    I agree with that given the current technology. The power consumption would have to reduced to femto-watt levels, maybe lower if antenna size shrinks in proportion to circuit size. The only application I see on the near horizon is microscopic "bugs" that "phone home" when properly triggered by a...
  17. hevans1944

    Op Amp Circuit Noise

    This is an ill-conceived circuit. Clearly the load is high impedance, hence the attempt to "measure" the load voltage without "loading" by using op-amp B with an inverting input configuration and a 1 MΩ input resistor. This in conjunction with a 10 kΩ feedback resistor, yields a gain of 10,000...
  18. hevans1944

    Removing circuit

    Hobby shops sell nesting, telescoping, brass and aluminum tubes. You might find one with right inside diameter to compress your plastic thingy enough to allow it to be removed from the circuit board. Or drill a shallow hole into the end of a plastic or steel rod, the hole being of appropriate size.
  19. hevans1944

    Need to replace DC gearmotor with a stepper one

    Here is an interesting page by a Do-It-Yourself solar-energy builder that might give you some inspiration.
  20. hevans1944

    Need to replace DC gearmotor with a stepper one

    What?! Forty foot-pounds of torque to move a few dozen linear feet of solar reflectors?! Someone has not properly engineered this project. If the reflectors are mounted on ball-bearing saddle-block end supports, and properly counter-balanced, you should be able to rotate them with your finger...
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