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  1. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Helder, Yeah, the problems with this project are frustrating. I would have updated it but I don't need it. A few people have built the improved one with success so maybe I'll update the project. It is a kit. Maybe errors were made on purpose in its schematic and parts list so that copies...
  2. audioguru2

    Audioguru FM Tx

    Hi Walid, Good point! I guess I don't follow my own advice. :-[ The FET in the mic isn't a perfect current source, its current drops a little when its voltage is reduced. My tiny electret mic came from a cell phone and has a current of only 0.25mA in my circuit. Most electret mics draw 0.5mA and...
  3. audioguru2

    BJT biasing formulas

    The hard drive on my 486/100MHz pc broke on Dec 26/04. On Dec 27/04 I bought a Pentium4/2.93GHz name-brand pc and 19" LCD monitor on sale with many manufacurers' rebates. On Dec 28/04 I got most of my money returned to me because I spotted an ad with a better price and my store guaranteed to...
  4. audioguru2

    Electronic Memory!

    Do they make a CD-Rom/CD player with an audio output? The ones on my pc's don't. I have seen many people with a portable CD player but haven't seen anyone with a pc's external  CD-Rom player connected to a battery pack.
  5. audioguru2

    Electronic Memory!

    I don't think a cap would power a pc with a CD-Rom/player for long enough for the engine to start.
  6. audioguru2

    PNP and NPN replacements

    You have to be a certified plumber to work on electronics that operates that high. ;D
  7. audioguru2

    Electronic Memory!

    You said you had a "(pc cd-rom) CD-player". A pc is a personal computer, isn't it? I suppose you could make an un-interruptable power supply for it, using a rechargable battery to keep it going as you start the engine. Alun had the same idea but he beat me to posting it!
  8. audioguru2

    BJT biasing formulas

  9. audioguru2

    PNP and NPN replacements

    Correct. We are using higher frequencies now. New wireless phones for homes operate at about 12.xGHz. My old one operates at 900MHz which is high enough for me. NASA uses some extremely high frequencies.
  10. audioguru2

    DSB power

    Hi Yousef, I haven't looked at math like that for about 40 years but I'll try answering your question. It looks like it is calculating average suppressed-carrier (?) DSB AM modulated power. I think the 2nd part of the equasion is zero because it is the minimum power and the 1st part is the peak...
  11. audioguru2

    Electronic Memory!

    Hi Mukhalled, The CD/MP3  player in my car radio remembers what it was doing when the power was shut-off. It plays my wifey's Spanish music nearly every time I get in. My pc remembers where it (or my wifey) was surfing on the internet or anything else it was doing. My digital cable TV box...
  12. audioguru2

    IC output help

    The datasheet mentions having a "star" ground where all things are grounded at one point, as shown on the schematic I posted.
  13. audioguru2

    BJT biasing formulas

    My rule always works, the rule in your tutorial fails when the transistor's gain is low like in power transistors. Take your pick which rule to use. You don't understand that the bias voltage divider is for the transistor's DC operating point. AC won't be affected if the coupling cap is big...
  14. audioguru2

    BJT biasing formulas

    Forget about only less than a 1% difference, the tolerance of the resistors and coupling cap will be 5% won't they? Years ago I was taught 26mV, but new transistors' datasheets show it is wrong.
  15. audioguru2

    Led display Digital Voltmeter question

    Hi Gruber, I think the 12V and 5V supplies are too closely related to work. I think this digital meter project needs a supply that is completely separate from what it is measuring.
  16. audioguru2

    BJT biasing formulas

    I made a minor mistake near the beginning of my calculations so IE is still 0.55mA but the collector voltage is roughly 4.5V instead of the desired 5.5V. I tried changing the 330k bias resistor to 360k, changing the 47k bias resistor to 43k and other combinations when I realised that when the...
  17. audioguru2

    Audioguru FM Tx

    An electret mic works well when operating at its spec'd 0.5mA. Half the supply voltage across the mic determines the resistor's value. The circuit's gain requirement depends on the sensitivity of the mic, how much the Q1 transistor circuit loads-down the mic, the gain of the Q1 circuit, how much...
  18. audioguru2

    Audioguru FM Tx

    Hi Walid, I calculated the circuit starting from my guess of 2.25V at the emitter and ended-up with 43.19uA through the 47k resistor which is supposed to be 44.48uA. Don't forget that the voltage across the 47k base bias resistor isn't 5V.
  19. audioguru2

    Led display Digital Voltmeter question

    Hi Gruber, I think our digital meter project cannot measure its own supply, so the A-meter for the 5V supply will need a separate supply. When you have both a V-meter and an A-meter for a supply, the V-meter should indicate the voltage at the load, because the resistance of the A-meter will...
  20. audioguru2

    problem Led

    Reneh wants to use a switch to turn the LED on and off. Maybe he doesn't know it needs a power supply.
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