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  1. audioguru2

    Need help for a heartbeat detector!

    Hi Fate, A PIC is a microcontroller that you must program like a computer to do counting and display multiplexing. You could use many separate oscillator, counter and gate ICs instead.
  2. audioguru2

    Trace problems

    Hi Carlton, Good, you fixed it by deguassing it. I never thought of using an electric razor as a degausser. Maybe its noise helps to random-orient the magnetism! ;D You know what shipping companies do with labels: FRAGILE. Throw it and see how high the package bounces. MAGNETISM. Can't see it...
  3. audioguru2

    VGA splitter - cropper

    Hi Nikolas, Sorry, I thought you wanted to make an offset. Sure, send a H-sync pulse to an output monitor then send it the video, and block the original sync and the parts you don't want to be seen on it. Its picture will be small, the same percentage of the total screen as the original. What...
  4. audioguru2

    FM WAVE PROPAGATION

    Hi Prateek, He, he. My FM transmitter goes that far? ;D I am still tweaking my FM transmitter and frequently its output isn't modulated. It must be jamming radio station reception on FM radios with a "blank spot on the dial" all around me. I've got RF coming out of my wing-wang. It is all over...
  5. audioguru2

    TELEVISION

    Allow a DC supply to power an oscillator called the horizontal one in a TV. The oscillator passes its AC output to a transformer called the flyback one in a TV. The high voltage AC output of the transformer is rectified and cap filtered into high voltage DC. Sometimes a voltage doubler or...
  6. audioguru2

    Electronic Stethoscope 2

    Hi Doctor Emad, How many did you make? There is nothing in the circuit to fail except the batteries. Maybe the input or output coupling capacitor is installed with incorrect polarity. After a while, it won't pass low frequencies. I recall that a few years ago many Chinese electrolytic...
  7. audioguru2

    Electronic Eavesdropping Devices Detector

    Hi Badai, A picture of a bare PCB and its parts layout is in the article for the project.
  8. audioguru2

    VGA splitter - cropper

    Hi Greek, Your idea will result in the left part of the picture missing and replaced by black. You need to delay the video by digitising it, storing it in RAM and play it back as VGA after your offset time has past.
  9. audioguru2

    TELEVISION

    Hi Prateek, See? You don't know that a TV has a flyback transformer to drive the horizontal deflection of the beam and to generate the extremely high voltage to make the beam. Some TVs also work when powered by the 12V fom a car battery. They don't have or need 220VAC. Therefore I recommend...
  10. audioguru2

    Need help for a heartbeat detector!

    Hi Fate, TTL counter ICs require the voltage from a logic low source to be 0.8V or less. The output of a 741 opamp won't go that low, probably 1.0V or more. The other opamps have outputs that go down to within millivolts from ground. I lost the whole article but the PIC was probably used as a...
  11. audioguru2

    Trace problems

    Hi Carlton, Welcome to our forum. Nice 'scope. Do you have something with a magnet nearby, like a speaker? The magnet will pull the ray. Maybe the case of the 'scope or something inside is magnetized. It would be very time-consuming to locate the magnetism, so get a small magnet ('fridge...
  12. audioguru2

    TELEVISION

    Hi Prateek, Stay away from the inside of a CRT TV if you don't know about them. The CRT operates with a voltage up to 25KV and it can be stored in capacitors for a long time after the TV is turned-off.
  13. audioguru2

    Electronic Eavesdropping Devices Detector

    Hi Badai, I don't think a metal box is necessary for this project because it doesn't have much RF gain. Lots of circuits can detect signals up to 108MHz and higher, they are called radios and TVs.
  14. audioguru2

    Coupling capacitors!

    Hi Prateek, You can call the current in a charging and discharging capacitor circuit "displacement" or any other kind of current name. There is actually real current flowing, it is not psuedo current. The ripple current flowing into and out of a filter cap heats the cap due to its Equivalent...
  15. audioguru2

    AM to FM convertor

    Hi Andbor, 24 guage wire is very thin and doesn't have the surface area to carry high frequencies which is required due to "the skin effect". The coil also won't stay in shape if it gets bumped. I got 1mm enamelled wire from an old transformer, but shops probably have it too.
  16. audioguru2

    Need help for a heartbeat detector!

    Hi Fate, A 741 opamp won't work with only a 5V supply, and its output won't go anywhere near ground for a proper logic low. The LM358, MC3358, MC3458, MC33072 or MC34072 will work much better, and they are all duals to match the pinout in the article.
  17. audioguru2

    in search of a FM STEREO transmitter

    Hi Ras, The kit comes with a coil former and an adjustable ferrite core. I would just make a simple coil with 8 to 10 turns of 1mm enamelled wire tightly wound with a 3mm air core, and use an adjustable 5pF to 35pF trimmer capacitor for tuning. The 2 bigger inductors can be purchased. You can...
  18. audioguru2

    square to sine convertor

    Thanks Guys, When I first saw that new appl note, I built a buffered phase-shift osc and fixed its problems with a 4th opamp. I used 3/4th of a 4-gang pot I got out of a toy. It works great. Using a little low-droppout regulator, its amplitude is rock-solid and its distortion is very low. ;D
  19. audioguru2

    Need help for a heartbeat detector!

    Hi Bird, You didn't look it up on Google, did you? National Semiconductor's sales information sheet says that the AM suffix is for a tiny surface-mount package. You probably want a DIL package for through holes mounting with a suffix of N.
  20. audioguru2

    Coupling capacitors!

    Hi Prateek, Sure, displacement current occurs when a capacitor is charged or discharged. One plate is stripped of electrons while the other plate has plenty when charged. Discharging developes a current that equalizes the charge of the plates.
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