Search results

  1. audioguru2

    MOSFET for high voltage and high power

    Hi Plouf, Welcome to our forum. Is your lamp's power supply AC or DC? Is the lamp an incandescent (with hot filiament) type or flourescent? An incandescent bulb that draws 1A when hot will draw 10A or more when cool so a transistor rated at 1A will go POOF! A Mosfet or bipolar transistor is...
  2. audioguru2

    Pb-free soldering

    Only if they look pretty when made into jewellry and don't corrode. ;D
  3. audioguru2

    detector prototype

    Hi Badai, I have added R17 to your schematic at the location the author has on his parts layout drawing. I have never seen a VCO circuit like that, so try it with and without R17. R17 probably limits its highest frequency, or turns it off without an input.
  4. audioguru2

    FM WAVE PROPAGATION

    Hi Prateek, In my country, the AM and FM broadcast bands are for the public, not the military. The military and others have their own bands.
  5. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Thomas, Gambling? What are those 50V opamps going to do in the summertime when it gets cool at night and all the AC in your neighbourhood turns off? They will suddenly be powered with 53V or more. Why not add a few turns to your transformers to raise their loaded voltage to 30V, and use...
  6. audioguru2

    detector prototype

    Hi Badai, None of the "general purpose" common audio amplifier transistors that I have listed will work above about 200MHz to 300MHz. To receive 1.9GHz, you need a microwave transistor better than the BRF90A, which can receive up to only about 1GHz. The BRF90A has no gain at 6GHz, a little gain...
  7. audioguru2

    detector prototype

    BTW, the circuit doesn't have a negative supply, just a single 9V battery. The terminal labelled "-9V" is very confusing. Your 1N4148 detector diode also won't work at high RF frequencies. Didn't we discuss it before? Use a 1N34A germanium diode or equivalent instead.
  8. audioguru2

    detector prototype

    It looks like the author missed R17 on his schematic, from pin 12 to ground like R15 on the other side. In my country, cell phones operate at GHz frequencies. A 300MHz 2N3904 won't work unless an operating cell phone is very close to it. I don't know why you re-drew the schematic without using...
  9. audioguru2

    AAA Battery Charger

    Hi Smart, Why not use a battery charger IC? www.maximic.com have some nice ones. Read about rechargeable batteries in our Articles section, and also at www.energizer.com .
  10. audioguru2

    square to sine convertor

    Hi Prateek, A single integrator won't convert a square-wave to a sine-wave. Many integrator stages will attenuate the fundamental frequency as well as its harmonics. That's why I recommended using a multi-pole Butterworth low-pass-filter, because of its sharp cutoff. Opamps don't have feeble...
  11. audioguru2

    CMOS power use?

    Yeah, Cliff is making a timer with a 4093 as a low-frequency RC oscillator, not a high frequency crystal oscillator. It can clock only 14 other Cmos ICs with no problem about fanout. At the slow speed of the counter ICs, I doubt you could measure any power supply current for them. Instead of...
  12. audioguru2

    [ARTICLE] How to rebuild a Li-Ion battery pack

    How much would you have to pay a mechanic to "rebuild" the hundreds of Ni-MH cells in a new Toyota Prius hybrid gasoline/electric car? It would probably take him days to replace them all, and how much cost for each cell? Instead of paying mechanic's charges, it is cheaper to buy a whole new car...
  13. audioguru2

    [ARTICLE] How to rebuild a Li-Ion battery pack

    He, he. Yeah, those electric trucks have huge batteries!
  14. audioguru2

    TELEVISION

    How little current flows in you if your skin measures 200K ohms and you have only 3V? 15uA. You don't feel it. Put a 9V battery on your nice wet, conductive tongue. You can taste the current and I think it feels warm. I haven't measured the current. Try it again after eating something very...
  15. audioguru2

    TELEVISION

    The voltage determines the current which is determined by how much you are sweating. It takes many volts to make a noticeable current to flow in your body. Maybe very high voltage burns a hole in your skin to make a nice conductive path inside your wet guts.
  16. audioguru2

    fm tranismiter

    Thanks Alun, I started investigating a circuit somebody posted that had its preamp transistor biased wrong and had no feedback. It was saturated with a new battery or when warm, and cutoff with a 7.5V battery or when cold. It also had horrible distortion with any battery voltage. Without...
  17. audioguru2

    TELEVISION

    Hi Rhonn, What is more dangerous, working inside a TV with a 46" CRT or trying to lift it?! ;D I saw one (Mitsubishi) with that huge CRT and it was so sensitive to the earth's magnetic field that it had a switch on the back for the direction it was facing. Years ago TV techies worked with one...
  18. audioguru2

    fm tranismiter

    Hi Dazza, Its fairly high RF power of about 250mW is very illegal down under. It overloads cheap radios and fills their dial within about 30m. A good jammer! Your limit is only 10mW (only if you get caught). ;D I used a tight layout on Veroboard and used ceramic decoupling caps at important...
  19. audioguru2

    detector prototype

    Hi Badai, Transistors having that unique package and pinout are made for very high frequencies. I found one in a cheap cable-TV amplifier box. Show the picture of the transistor at your local shop and they might have an equivalent one. Otherwise, an ordinary general-purpose transistor like a...
  20. audioguru2

    TELEVISION

    Hi Prateek, You can have voltages higher than the supply voltage in tuned LC circuits but most stepup transformers are not tuned by a matching capacitor equaling their inductance. They stepup the AC voltage due to magnetic coupling between their windings and the ratio of turns of the windings...
Top