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  1. audioguru2

    inverter oscillator

    Pullup? Which inverters? CMOS? What power supply voltage? We would like to help you but we don't know what you have. Can you sketch it?
  2. audioguru2

    Supa Dupa Basic Timed Latched Relay

    Ante, A diode across a relay coil does slow its release, because it causes the current to continue during the collapse of the magnetic field. Since the enormous cap would be in series with the small switch contacts, without any current-limiting, then the charging current will be huge, more than...
  3. audioguru2

    Supa Dupa Basic Timed Latched Relay

    Ante, No high-tech? Thats a supa dupa good idea! Just think about his poor little switch contacts if they attempt to charge that enormous cap. A diode across a coil slows its release too.
  4. audioguru2

    Wannabe Secret agent man?

    ZomBiE, That's cool. I'll bet that it frequently indicates "low batt" when transmitting. Carry a bag full of batteries if you have much to say.
  5. audioguru2

    Square wave to Sine wave

    Graeme, I thought that all mechanical generators produce sine waves. It would be complicated and expensive to make their output a square wave. Are you talking about an inverter, or voltage converter, that runs off a battery? They usually have a square wave output, and it would be complicated and...
  6. audioguru2

    Supa Dupa Basic Timed Latched Relay

    Laet, Without a transistor, your circuit won't be very supa dupa. You will need about 330,000uF across the 90 ohm relay coil. Thats 330, 1000uF capacitors, all in parallel. Or use a big, expensive cap that is used for high-power car audio. :( With a transistor, a resistor and a diode, you need...
  7. audioguru2

    decoding a 10khz tone!

    Qasim, Why is there a 10KHz tone on an FM station? ??? Listeners with good ears and good speakers would complain, and it would be very hard on their tweeters. There is a 19KHz tone, which is the stereo pilot tone, which can be measured if you filter it from the lower frequency audio and upper...
  8. audioguru2

    RJ45 network card to IR

    Stuee, RS seems to sell only stuff that I haven't used for about 30 years, like old-fashioned standard TTL. Don't you have good English suppliers such as Mappin or Farnell over there? Any members from "down under" to help him out?
  9. audioguru2

    Question on the Plants Watering Watcher circuit

    Ante, As a soil moisture indicator, two 1000mA/hr (to 1.0V) alcaline AAA batteries should last a couple of years! The PWM of this circuit is logarithmic, so when the resistance of the soil is half-way to being very dry, the power to the LED is not also half, but actually only 1/10th, which looks...
  10. audioguru2

    Question on the Plants Watering Watcher circuit

    Hi guys, My "flashing LED" revision that I made to this project works perfectly. ;D ;D Since the LED is powered for such a short time, 2 AAA batteries will last a long time. The flashes are bright when the soil is dry, attracting your attention before the thirsty plant wilts. It even flashes...
  11. audioguru2

    extrosonic anybody?!?

    Daniel, Why is your country "backwards" just because it uses 240VAC? Your house-wiring is thinner, cheaper and easier to work with. Over here in my "forwards" country (Canada), my house wiring is so thick that it is difficult to push a flush-mount outlet to its wall-box. Also over here...
  12. audioguru2

    OUTPUT IMPEDANCE

    Here's my attachment again:
  13. audioguru2

    OUTPUT IMPEDANCE

    Shiva, I have sketched a simple schematic for measuring the output impedance of an amplifier. For R, use a low-value resistor, such as 10 ohms. Use a signal generator that is capable of driving such a low resistance, or use an amplified generator. 1) Measure the signal voltage at the injection...
  14. audioguru2

    LED Circuit

    Hotwaterwizard, The knightrider circuit will work fine on 12V.
  15. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Capricious, Welcome to our forum. You are right, this project has created much confusion since its specified parts don't seem to do the job unless you are very lucky and don't use it at its limits. Shown above is a link to the other forum where boosting its output to 5A is discussed. I...
  16. audioguru2

    pulse width modulation

    Kevin, The fact that the input voltage threshold of a CMOS inverter is at half-supply is very important to the operation of the classic CMOS 2-inverter oscillator, and is also important for its use in PWM. The threshold is at half-supply because the N-channel and P-channel MOSFETs are...
  17. audioguru2

    pulse width modulation

    Kevin, Your observations: 1) Sort of. I wouldn't say that the high output of the 2nd inverter GOES THROUGH the cap (but I know what you mean). I would say that since the cap is discharged and has 0V across it, and since it is connected to the output of the 2nd inverter, then its other end that...
  18. audioguru2

    pulse width modulation

    Kevin, You have questioned the operation of a classic CMOS oscillator many times before, so I would like to explain its operation to you: A) The 2 CMOS inverters have an input threshold voltage of mid-supply. If a CMOS gate is used as an inverter, only one input should be used to keep the...
  19. audioguru2

    0-30 Vdc Stabilized Power Supply

    NightHawk, It sounds like transistor Q1 is not working. When you shut off the power, the negative supply voltage across D7 is supposed to disappear very quickly, since it has a small filter capacitor. Q1's base is biased by the voltage divider of R13 from the positive supply voltage of about 36V...
  20. audioguru2

    actually a quad amp....

    Thanks, MP. So the only difference is that the TDA1558 has 10 times more built-in gain than the TDA1554. Why would anyone need a voltage gain of 200, in a bridged audio amplifier that delivers only 8V? A voltage gain of 20 is usually plenty.
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