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  1. hevans1944

    Hello, varactor(varicap) formula help

    It is now obvious to me that you still have zero understanding of how a varicap or varactor diode works. Also, it appears that you do not know how to read a datasheet. In the quote above that you made, you mention a book but did not bother to mention the title of the book, the author, or when...
  2. hevans1944

    Simple Low Frequency Sound Generator

    No doubt both are responsible. The phone doesn't provide enough audio power to the speaker, and the speaker is inefficiently coupled to the brain cavity. Why not? Just remove one of the them from the headband and press it against the forehead. Probably still won't be "loud" enough, but you can...
  3. hevans1944

    Simple Low Frequency Sound Generator

    A hand-held medical device, huh? Monaural rather than binaural? Here is a website to get this forum's participants started on the fascinating subject of brainwave entrainment, which is not necessarily what the OP is actually working on. So please don't hijack this thread to go off on that...
  4. hevans1944

    Change Username

    You have only been registered since October 24, 2017, and have posted only 16 messages since then, none of which we can look up because "you limit who can view your full profile." So abandon the username @Electrical_Shocker and register under a different user name. No one will care and almost no...
  5. hevans1944

    Integrator and Voltage Follower Testing

    I don't think you do understand. The most important specification for an op-amp configured as an integrator is the bias current produced at the differential input terminals. This should be as small as possible to minimize drift in the output when no signal applied. However, drift is inevitable...
  6. hevans1944

    Simple Low Frequency Sound Generator

    Welcome to Electronics Point, @Clemson2019. So, are the responders here at EP left to produce a 128 Hz sinusoidal oscillator that drives a three or four inch diameter speaker with ten watts of power delivered from a disposable battery? And are you coming to this forum for help because you (1)...
  7. hevans1944

    Simple Low Frequency Sound Generator

    Then, if you use the binary divider approach from a 32.768 kHz crystal-controlled oscillator, you will need to follow that with either a narrow band-pass filter tuned to 128 Hz, or a low-pass filter that attenuates the higher frequency harmonic content of the square waves. Either way, ten watts...
  8. hevans1944

    Capacitor problem

    Why did you replace the original, burned up capacitor, that was rated 25 μFd (+10% -0%) at 250 V AC 50/60 Hz with a much larger capacitance of 200 μFd and much lower 125 V AC rating? I would also suspect, and test for, a centrifugal switch that isn't operating properly. Something caused the...
  9. hevans1944

    Hello, varactor(varicap) formula help

    @michael1978: Because of the DC bias required to change the capacitance of varactor diode, the usual test equipment, such as a muiltimeter with a capacitance-measuring function, may not work very well. Also, because the capacitance is quite small and is easily affected by the connecting wiring...
  10. hevans1944

    Hello, varactor(varicap) formula help

    Check this page for specifications. You generally have to isolate the varactor diode from the resonant circuit that it helps to tune. You do this by inserting a series capacitor of at least ten to hundred times the maximum varactor capacitance. Without this capacitor any inductance present in...
  11. hevans1944

    Nichrome wire heating project. help please!

    You are correct: methanol is used as racing fuel. It is especially dangerous because it burns without a visible flame. Not sure about how methanol behaves as a fuel compared to gasoline, but 10% ethanol mixed with various octane grades of gasoline is routinely delivered by gasoline pumps in the...
  12. hevans1944

    Nichrome wire heating project. help please!

    Biodiesel seems to be a viable alternative to gasoline. You could probably run the entire British taxicab fleet using biodiesel recovered from McDonald's used cooking oil. Have you thought about also placing a "dip stick" type heater in the fuel tank to help liquefy the biodiesel fuel? These are...
  13. hevans1944

    Nichrome wire heating project. help please!

    @Slowbutsure, I am curious as to why you want to heat your fuel filter? Is this a diesel-fueled engine that is susceptible to fuel-line freezing because of the poor quality of the diesel fuel, or water condensation in the fuel tank? If it is a gasoline fueled engine, I would be worried about...
  14. hevans1944

    Nichrome wire heating project. help please!

    The link was to a specific product offered at grainger.com, but perhaps that page was filtered out before it reached you because of your location in the UK. Here is another link to an alternative sensor that automatically resets and is less expensive. I am also going to attach a PDF copy of the...
  15. hevans1944

    Nichrome wire heating project. help please!

    No. You need a temperature sensor to reliably prevent a temperature rise above 70 C. Here is one that opens at 180 F (~82 C). Just wire it in series with the heater and it will remove power when the surface reaches the switching temperature. This sensor is based on the Texas Instruments...
  16. hevans1944

    Nichrome wire heating project. help please!

    Quit wishing and learn how to make Google your friend. Try this link to get stuff from Wal-Mart shipped to your address in the UK by using a parcel forwarding service. BTW: It's a world economy now in the 21st Century. Buy from anywhere, ship to anywhere with sufficient incentive and...
  17. hevans1944

    Nichrome wire heating project. help please!

    Why bother building when you can buy this one all ready to go at Wally-World? Just add a thermostat and 20 A wiring between the pad and your car battery. Of course you should bone up on thermodynamics to understand how this thing will get hot, and how it will transfer that heat to the...
  18. hevans1944

    Electrolytic capacitor identification

    Try visiting the links on this Google results page. Possibly a 220 μF, 50 V, electrolytic capacitor.
  19. hevans1944

    LED in distilled water?

    That's pretty cheap, considering drug store mineral oil is USP grade. But you don't need gallons of the stuff. Just enough to circulate around the LEDs and their heat sink to a place where you can remove the heat. A few ounces would probably be enough, depending on the size of the LED array...
  20. hevans1944

    Strange part

    Truth! Probably no one here remembers the "good ol' days" of medical electrical and electronic quackery... it was a free-for-all of unlicensed practitioners using questionable devices to "treat" patients for every imaginable condition or disease. Testimonials abounded. but little scientific...
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