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  1. audioguru2

    RJ45 network card to IR

    Kevin, In the 1st and 2nd circuits that use a 9V battery, the IR signal is taken across the 1K resistor. The +5V is usually bypassed with a capacitor and therefore is at signal ground. It doesn't matter what the voltage is for the - terminal of the 9V battery, since it only affects the 1pF...
  2. audioguru2

    A stand alone sine wave generator using Atmel chip

    Kevin, You can also make a sine-wave from a square wave, just filter out the harmonics. Then you don't need an integrator. Your simple filter attenuates the HIGH frequency harmonics by rounding-off the sharp corners.
  3. audioguru2

    RJ45 network card to IR

    Which circuit works OK? Why was it completely re-designed?
  4. audioguru2

    0-30 Vdc Stabilized Power Supply

    Good news, Guys, I found a high-voltage, readily available and inexpensive replacement opamp for U2 and U3, which are operating in this project with a supply voltage beyond the maximum specified ratings of the original TL081 opamp. It is ONSemi (formerly Motorola) part number MC34071AP. Its...
  5. audioguru2

    Two-way Crossover, Audio Project

    Hotwaterwizard, Thanks for the tip for Carstereo's knowledge base. But their crossover component calculator doesn't work. Maybe I must login?
  6. audioguru2

    Light Switch

    Ante, Yes, let's get that transistor switching fast. The schmitt trigger, because of its positive feedback, will do that. Siddharth, That's a nice circuit that you have found but it can be improved: 1) The opamp is not a schmitt trigger because positive feedback is missing. Add a 100K ohm...
  7. audioguru2

    Unknow current in transformer

    Mikail, Welcome to this web-site. With an unknown transformer you must take precautions to ensure your safety: 1) Make certain that it is a mains-power transformer, not an audio one. 2) Make certain that you know which wires are the primary that connect to the mains. 3) Make certain that the...
  8. audioguru2

    A stand alone sine wave generator using Atmel chip

    Here is a programmable digital sine-wave chip developed by Fairchild awhile ago for telcos. They say that it uses "no external components". I haven't checked its availability. They talk about the phase-accumulators having interference causing distortion readings (0.1%) to be higher than it...
  9. audioguru2

    A stand alone sine wave generator using Atmel chip

    Groovy, Here is a project that uses a mini-micro to digitally bandpass-filter its internally-divided clock and over-sample it. Although it was limited to a max freq of 20kHz it may give you ideas for use with faster chips. The project is here...
  10. audioguru2

    RJ45 network card to IR

    I disagree with you, Serge: In all of your circuits, of course the IR diode is foward-biased, with its anode shown connected to +9V, +4.5V or +5V, and the cathode connected through a resistor to negative or ground. The diode is shown conducting forward current, all the time. Please check your...
  11. audioguru2

    TV: High Definition, Progressive Scan

    Hi Guys, Now that the American high-definition TV and progressive-scan DVD players are available here (Canada), I need to clear up some misunderstandings: 1) The TVs are still too expensive. Aren't many being purchased? Many DVDs are being rented/sold and I don't think that most are viewed on...
  12. audioguru2

    Power Supply +5v with Zener

    Ante, A zener begins losing control when it is conducting its "knee" current. A zener operating at its knee makes a lousy regulator. Did you know that the reverse-biased base-emitter junction of an NPN silicon transistor makes a pretty good zener at about 7V. But they say that the transistor...
  13. audioguru2

    Car stereo amplifier output ratings

    Hotwaterwizard, Mosfets beat bipolars because they are much more efficient when switching high currents. A mosfet has an extremely low on-resistance so that the load gets the most power, and they switch very quickly so that they spend very little amount of time dissipating power. There is a very...
  14. audioguru2

    OPAMP questions

    Kevin, A compensated (with built-in roll-off) opamp that is using negative-feedback IS stable because the roll-off makes certain that at high frequencies, the gain is reduced so that the circuit will not ring nor oscillate. The compensation ensures a good phase-margin. Stability of an opamp is...
  15. audioguru2

    Power Supply +5v with Zener

    A comparison between zener vs series voltage regulator: Example: 20V power source, 10V regulated voltage, 100 ma load current: Zener S.V. regulator Resistor voltage = 10V -...
  16. audioguru2

    Light Switch

    I agree with you Ante, A Schmitt trigger is better than a simple transistor since it will stay after switching, while a simple transistor may cause the lamps to flicker if a shadow falls on the LDR or a if cloud goes by. We still don't know how much current is required. Recall that an...
  17. audioguru2

    0-30 Vdc Stabilized Power Supply

    Juan, If you are referring to C7 in this project, check its polarity. Polarized capacitors make spectacular explosions if connected backwards.
  18. audioguru2

    Car stereo amplifier output ratings

    Hotwaterwizard, Do you remember when transistor AM radios were invented and most had 6 transistors? Well one brand had engraved on its case, "14 TRANSISTORS". I opened one up and counted, 7 for the radio (the 7th was used as a detector diode) and 7 connected together in a neat circle doing...
  19. audioguru2

    Power Supply +5v with Zener

    MP, A zener regulator is always conducting current while regulating, regardless of the amount of load current. The zener conducts its wasted current to ground, not to the load. The resistor feeding the zener must supply both the zener's and the load's currents. A series voltage regulator IC...
  20. audioguru2

    Light Switch

    Siddharth, 1) What are you going to use this voltage-changing circuit for? 2) How many volts will feed the regulator? 3) How much output current when its output voltage is high? 4) What voltage output do you need when it is dark? 5) What voltage output when it is in bright light? The transistor...
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