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  1. audioguru2

    Upload Folder is Full

    Maybe we should chat and attach schematics on another electronics chat site then provide a link to it on this site.
  2. audioguru2

    Upload Folder is Full

    Now the upload limit is 0kb.
  3. audioguru2

    0-30 Vdc Stabilized Power Supply

    Q2 is broken. Replace it.
  4. audioguru2

    Frequency to voltage conversion

    The input needs a 100k resistor to 0V and a 0.1uF coupling capacitor like this: EDIT: Sorry, this site won't let me attach my corrected sketch. It says that my upload folder is full.
  5. audioguru2

    0-30 Vdc Stabilized Power Supply

    Mistakes quickly blowup parts. The output voltage of U2 will go as high as it can because of the negative feedback through R12. The opamp's negative feedback senses that the output voltage of the project is too low and is trying to correct it. If the base voltage of Q2 is high but its emitter...
  6. audioguru2

    Does Infra red get reflected from white surface?

    Hi Shaiq, Something that looks white reflects all colors, usually including IR. Something that looks black absorbs all colors.
  7. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Mat, Welcome to our forum. ;D Does "no voltage" mean a voltage of 0V at the output? Then the negative feedback through R12 will normally cause the output of U2 to go high, so the voltage at both ends of R15 should also be high, then the emitter of Q2 should also be almost as high (minus about...
  8. audioguru2

    Frequency to voltage conversion

    Hi DarkBlueSky, Welcome to our forum. ;D It would be easier to see how you connected your circuits if you attached a sketch, but maybe this site has a problem lately with attachments. The LM2907-8 needs to have a resistor from its input to 0V, then the signal should be capacitor-coupled to it...
  9. audioguru2

    rf coil

    Assuming that your cell phone operates only on a frequency between 800MHz and 900MHz (mine operates on many more frequencies), the tuning of the bandpass filter will be very wide. Don't you think the circuit would pick up every RF signal between 800MHz to 900MHz that is around?
  10. audioguru2

    Upload Folder is Full

    I hope that Mixos finds that it is a mistake and corrects it.
  11. audioguru2

    stereo Transmitter

    A 555 is not anywhere near accurate enough as the 76kHz stereo oscillator for a BH1415. The datasheet for the BH1415 mentions using a very accurate 76kHz crystal instead of a 555. The stability of the RF section of the BH1415 is also poor. The newer BH1417 uses its crystal's accuracy for both.
  12. audioguru2

    Darlington TR

    Let me try again to upload a pic of transistor distortion: EDIT: Nope, my upload folder is still full so I can't attach anything.
  13. audioguru2

    Veronica PLL

    I posted a new topic about the "Upload Folder is Full" problem. The Veronica FM transmitter without the PLL is not legal to use in Britain, because its RF frequency drifts all over the place. Look in Google at Phase-Locked-Loop and you will see that it has an accurate crystal oscillator, a...
  14. audioguru2

    Pulse Width Modulation

    A frequency counter instrument will show its frequency. My digital multimeter has an accurate frequency counter function.
  15. audioguru2

    Simple DC motor PWN speed control

    A permanent magnet motor has its max current when its shaft is stalled. When mechanically overloaded and when it begins to run. It also has a very high current at the moment its direction is reversed. The max current is the supply voltage divided by the motor's resistance.
  16. audioguru2

    stereo Transmitter

    The RF frequency is not stable, like "toy" FM transmitters and changes with temperature change, supply voltage change and when something gets near its antenna. The web has nasty stories about cheap kits that use Rohm's BH1404 FM transmitter IC that also drifts. Some countries do not allow FM...
  17. audioguru2

    Upload Folder is Full

    Lately, a few people have not been able to attach things and get an error message "Your Upload Folder is Full". I understand that webspace has a cost, and a few of us make a lot of attachments, but if we are limited in the amount of attachments we can make then maybe we should chat on other...
  18. audioguru2

    Darlington TR

    Here is a pic of transistor distortion without having negative feedback from an unbypassed emitter resistor: EDIT: Nope. I am not allowed to upload any more because my upload folder is full!
  19. audioguru2

    Darlington TR

    Without having about a 10uF capacitor as a bypass across the 1k emitter resistor, the voltage gain is only about 3.6. With the bypass capacitor, the output is very distorted at high levels. Sorry, I can't upload a pic of the distortion.
  20. audioguru2

    stereo Transmitter

    Here is a pretty good article about the theory of FM stereo with some links at the bottom about Rohm's older ICs: http://members.tripod.com/~transmitters/stereo.htm
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