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  1. audioguru2

    Oscillator drift

    If you are calculating my FM transmitter's oscillator frequency, don't forget to add about 10pF stray capacitance to represent the pcb wiring capacitance, the transistor's collector capacitance and a contribution of the feedback capacitor. If the value of my 0.1uH inductor is correct, then the...
  2. audioguru2

    Audioguru FM Tx

    Hi Alun, We were comparing my 10.5 turns, small diameter coil with his 5.5 turns, larger diameter coil. Using the same tuning capacitor then his would tune to higher frequencies than mine because his coil's inductance would be less than mine. I don't think either circuit would tune to as high as...
  3. audioguru2

    Reduce DC voltage, How? please..

    Alun is correct. The minimum load current rating for a premium LM117 is 5mA. The R1 value is calculated 1.25V/5mA= 250 ohms. 240 ohms is the closest 5% resistor value and is shown in the application circuit on the 1st page of the datasheet. The cheaper LM317 has a min load current rating of...
  4. audioguru2

    Help with IR motion sensor

    Correct. Make a latch with a pair of cross-coupled NOR gates. Consider using power-up reset and a manual reset. ;D
  5. audioguru2

    Audioguru FM Tx

    I didn't design the tank, I just copied it and many other ideas from Rod Elliot's project: http://www.sound.westhost.com/project54.htm I didn't measure the inductance and I just used little trimmer capacitors that I had. The minimum capacitance of the trimmers is definately not only 5 pF due to...
  6. audioguru2

    Help with IR motion sensor

    That's correct. The circuit doesn't have a latch on its output so it could be used to count cars driving by or somethin'.
  7. audioguru2

    Current Limiting Indication

    Since an ordinary transistor turns on with only "0.2V" across the current-sense resistor, then the voltage must be full of spikes. Threfore the voltage must be filtered (causing delay) to be sensed by a comparator. The IC already has a comparator with inputs at pins 4 and 5 , a filter for them...
  8. audioguru2

    Help with IR motion sensor

    If the circuits were integrated side-by-side and pointing in the same direction then they could be beaming and receiving the IR from a mirror on the other side of a corridor to be monitored. An intrusion would break the beam and signal the alarm. If the intruder had his own mirror or modulated...
  9. audioguru2

    Bass/Treble System

    Hi Mukhalled, I'm glad you understand. I remember when you built the amp and complained about its distortion when you turned up the volume. The overloaded amp was complaining back to you! If you add resistors in series with the speakers to increase their total impedance to the amp's 4 ohm...
  10. audioguru2

    Bass/Treble System

    Hi Mukhalled, A multimeter measures DC voltage and current, AC voltage and current, and DC ohms. The AC voltage might be measured in "true RMS". To measure impedance you need a signal generator with a known output resistance that feeds different frequencies to the load to be measured. You...
  11. audioguru2

    Bass/Treble System

    You don't need to measure anything! Just read the labels on the speakers, use a little common sense and calculate their parallel impedance.
  12. audioguru2

    Bass/Treble System

    Mukhalled, You can't measure impedance with an ohmeter, just measure resistance. You can't measure the resistance of the tweeters because they have a capacitor in series with them. You can't measure the resistance of a channel including the woofer because the woofer is connected between...
  13. audioguru2

    Bass/Treble System

    Hi Mukhalled, You said you disconnected the amplifier and added resistors in parallel. Then you posted a sketch with "a  4 ohm resistor" added in parallel. Post a sketch of how it is wired including the resistors you added!
  14. audioguru2

    Bass/Treble System

    Hi Mukhalled, Don't do that! By adding 4 ohms to the amp now its load impedance is 1.33 ohms. Hi Staigen, Mukhalled previously sketched the speaker system that shows each channel with a 2 ohm load at high frequencies, and a 2 ohm load at low frequencies, with the heating brilliantly divided...
  15. audioguru2

    GO BEARS!!!!!!

    I thought it was a baseball team. Silly ballgames. I was given tickets with expensive close-up seats to an international hockey playoff. I took my son and was amazed the rink looked much smaller than on TV. What a bore! They played for 2 minutes then took a 20 minute break, over and over. I...
  16. audioguru2

    0-30 Vdc Stabilized Power Supply

    I recommend changing D8 and Q2. Change the values of R4 and R15. Then it will work as well as it can. If parts melt, upgrade them. We don't know how low the transformer's output voltage will be with a heavy load, so we don't know what your project's max output voltage will be without any ripple...
  17. audioguru2

    Bass/Treble System

    Hi Mukhalled, If the 3-way speakers and the tweeters are all 4 ohms each, then each amplifier has a 3-way speaker in parallel with a tweeter and has a 2 ohm load at high frequencies. Therefore the amp is overloaded. You probably measured the DC resistance, but the capacitor in series with the...
  18. audioguru2

    a Constant Power consumption design

    Hi Shahriar, I don't like to see your zener diode starved of current when the supply voltage is only 4V, and cooking when the supply voltage is 32V, so I tried it with an LM317 regulator adjusted to 1.25V. I used a resistor on its output to hold its output voltage down. Then I added a common...
  19. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Helder, I'm glad to help you. ;D The voltage from your transformer is lower than we thought, resulting in a total supply voltage low enough that cheap 44V-rated opamps can be used. I think the negative supply will be fine when you replace the blown-up opamps that are installed now. ;D
  20. audioguru2

    Bass/Treble System

    How do you figure the impedance for each side? Car speakers are usually 4 ohms each. Therefore at high frequencies each side has a 3-way and a tweeter in parallel, resulting in 2 ohms. Adding the woofer lowers the resulting impedance at low frequencies the same. The TDA1554 IC is designed to...
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