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  1. audioguru2

    4 watt transmitter

    It is a Greek kit and project. D1 is part of the detector used to tune the project and is shown on the Greek version's page 1.
  2. audioguru2

    Simple O2 meter with LM3915

    Hi Wellington, Your project looks neat and tidy and it is wonderful that it works well. ;D
  3. audioguru2

    Stereo Audio power amplifier 2 x 40W - 80W

    The brightness of the LEDs is determined by their current. Their current is roughly 10 times the current out of pin 7 of the LM3915 . Your pin 7 is about 9.8V and has a load of 17.2k in parallel with the resistor ladder inside the IC so the total load is about 10.7k and its current is 0.92mA. So...
  4. audioguru2

    battery and HDD

    You cannot select another regulator with higher output current until you find out the max current of the HDD. You could look on the datasheet of most manufacturers' 78xx regulators where they show how to add a power transistor for nearly unlimited output current.
  5. audioguru2

    a hi fi amplifier

    HiFi is short for "high fidelity". The output of a high fidelity amplifier is the same as its input: very low added harmonic and intermodulation distortion, a wide flat frequency response and very little added noise. An audio expert said the perfect high fidelity amiplifier is "a piece of wire...
  6. audioguru2

    battery and HDD

    Your voltage regulator ICs can't supply enough current to the hard drive to get it spinning quickly. It draws a very high current when its speed is accellerating. Remember 8-track tape players that drew about 10A to change tracks??
  7. audioguru2

    A project, help

    Google will tell you more than me, but Cmos has a very high input impedance, has a very low supply current, works from 3V to 15V and 74HCxx high-speed Cmos is just as fast as 74LSxx. I think so. Intel and other computer chip makers also think so.
  8. audioguru2

    Audioguru FM Tx

    The TDA7000 and probably also the other IC are very simple and cheap. They don't make an FM radio as good as the home stereo tuner and car radio that I tested my FM transmitter's range with. Those cheap "radios" have an IF frequency of only 70kHz, so image frequency multiples of it might cause...
  9. audioguru2

    A project, help

    I haven't used an old 7400 for more than 40 years. I made set-reset flip-flops with them but since I have used Cmos and flip-flop ICs. Look for a set-reset flop-flop that uses TTL gates in Google.
  10. audioguru2

    Did anyone information about ...

    Good. I am glad that you will discuss electronics without your religion.
  11. audioguru2

    Low-pass Filter?

    If you use a single pair of output transistors in the modified 500W inverter project then it will have an output of 100W. It won't work without a transformer.
  12. audioguru2

    Frequency Generator - 2 Fixed O/P

    The function generator circuit with three opamps doesn't make a very good sine-wave. The triangle wave is smoothed with only a single RC filter so the distortion of the sine-wave will be high at about 8%. The old 741 opamp is very slow. Modern opamps are much faster and cost less.
  13. audioguru2

    Simple O2 meter with LM3915

    I wish all your PMs are in this thread so I can see them. I think you said that the brightness control worked backwards so I thought the LDR is a phototransistor. Now I see that I was wrong and they would both work about the same. The LDR is a low resistance when it is lighted, so if it is at...
  14. audioguru2

    Did anyone information about ...

    ??? ??? This is an electronics chat forum. Maybe it is best for him to leave his religion at home.
  15. audioguru2

    Simple O2 meter with LM3915

    Hi Wellington, Now the phototransistor is too sensitive. Add a resistor in series with it so it cannot dim the LEDs so much.
  16. audioguru2

    A project, help

    For more than 40 years, when I needed a flip flop then I used a flip flop IC. You can look in Google if you want to make your own.
  17. audioguru2

    6V 5A PSU problem.

    Since your 6V supply doesn't have a voltage regulator then its ripple is at 120Hz in North America. Your 15V regulators or opamp are oscillating at several MHz or the opamp is picking up a local SW radio transmission at several MHz.
  18. audioguru2

    A project, help

    The circuit in your box needs to be a flip-flop. A blink flips it on and another short signal resets it.
  19. audioguru2

    Simple O2 meter with LM3915

    Hi Wellington, Wow, your photodetector has a very wide range of resistance. Too wide for an LDR so I think it is a photo-transistor. No wonder its response is backwards. Swap its position with VR1 and the resistor connected to VR1 (R9?) but its ends must be swapped to keep the correct polarity...
  20. audioguru2

    Not Gate

    No. Transistors can be used as switches many other ways. Yes. You can add a 2nd transistor to make your own darlington transistor or buy a darlington transistor. Then the 100k resistor consumes very little current. See my modified schematic No. It is a transistor inverting switch. A digital...
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