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  1. audioguru2

    Fm transmitter

    Please attach your schematic here instead of over at RapidShare. The very old circuit will sound bad and have its frequency change when its supply voltage changes. I don't know where you will find a clip-on heatsink for the output transistor.
  2. audioguru2

    a few questions about Digital Step-Km Counter circuit/help

    Red Circuits originated many of the projects that are here at Electronics-Lab: http://www.redcircuits.com/ Except in his projects ten microfarads looks like 10uF and here it looks like 10^.
  3. audioguru2

    a few questions about Digital Step-Km Counter circuit/help

    Correct. The transducer in this project is a coil and magnet speaker, not a piezo transducer. RED does not have this project on his website anymore.
  4. audioguru2

    a few questions about Digital Step-Km Counter circuit/help

    The "piezo sounder" is not a beeper, it is a transducer (speaker) that is driven at about 2.7kHz by the oscillator made from IC1C and driver transistor Q1. C4 smooths the power supply voltage so it does not jump all over the place. IC3 and IC4 are counter/decoder ICs. They do the counting and...
  5. audioguru2

    Need Help Buiding the project using lm386

    Why don't you make the circuit that is shown in the datasheet for the LM386? The manufacturer recommends it. The kid who posted the project maybe never looked at the datasheet.
  6. audioguru2

    about RX-3 IC

    Hi Walid, Q1 is a super-regenerative "radio receiver". It barely oscillates which makes it fairly sensitive if it is not overloaded by other signals near its frequency. It is used in very cheap walkie talkies and remore controlled toys.
  7. audioguru2

    Fm transmitter

    The electret mic must be connected with the correct polarity. Its metal case has the wire that should be connected to the circuit's ground. The mic must be connected with very short wires or with a shielded audio cable. You must not touch any part of the circuit when it is transmitting to avoid...
  8. audioguru2

    hi !!!!!!

    The lowpass filter reduces frequencies above its cutoff frequency, it does not eliminate them. At double the cutoff frequency, the output of your simple first-order filter is -6dB which is half. At double the cutoff frequency, the output of a second-order lowpass filter is -12dB which is 1/4. At...
  9. audioguru2

    0-30V Stabilized Power Supply

    Hi Dracu, Farnell have offices in many countries including Romania. They have hundreds of both opamps in stock in Romania. Go to www.farnell.com . I buy electronic parts from their office in Canada.
  10. audioguru2

    0-30V Stabilized Power Supply

    You do not need to buy 100 MC34071A opamps at Digikey. They have many of them for a single quantity purchase. They have ordinary ones and "A" premium ones.
  11. audioguru2

    0-30V Stabilized Power Supply

    The opamps chosen are sold everywhere in the civilized world. Maybe not on your different planet. Digikey in North America and Farnell in many other countries sell the popular opamps. There are many newer opamps that can also work. Where are you??
  12. audioguru2

    0-30V Stabilized Power Supply

    You can add fine-tuning pots in series with the coarse adjustment pots but they will be always set to the wrong position. If you made the latest circuit with MC34071 or TLE2141 opamps then RV1 adjusts the 0V output to 0V if your voltage adjustment pot can give a 0V output. The output capacitor...
  13. audioguru2

    Inductor for FM Tx

    I think a super-regen FM "radio" is a piece of junk. It has an AM detector so it must be tuned to one side of an FM station so it can "slope-detect" the FM. It overloads very easily.
  14. audioguru2

    0-30V Stabilized Power Supply

    Hi Limbo, Your power supply looks good. I think the tiny 2N2219 Q2 driver transistor will melt if the output is shorted and the gain of the 2N3055 transistors is low. It will try to dissipate more than 3w which it cannot do even with a clip-on heatsink. A BD139 real power transistor should be...
  15. audioguru2

    Inductor for FM Tx

    The inductor values of my FM transmitter were just guesses. The construction of the coils was copied from a project that works and mine also works.
  16. audioguru2

    0-30V Stabilized Power Supply

    Hi Redwire, Here is the latest parts list that uses the new opamps. it is missing the 10v zener diode.
  17. audioguru2

    0-30V Stabilized Power Supply

    Hi PicMaster, The OPA445 high voltage opamp will not work in the latest modification. I didn't keep a schematic for the project with the OPA445 opamps because it was nearly the same as the original except for a couple of corrections. Here is the parts list for it: EDIT: Dec 13, 2013. 1) The...
  18. audioguru2

    What the value of Zout???

    Hi walid, I have not done RF work in my career and I haven't done school-work for about 42 years. The transistor is a linear amplifier so its collector swings down to about 4.5V and swings up to the same amount above the supply voltage because of the tuned circuit. So the voltage swing is...
  19. audioguru2

    power inverter

    An inexpensive little inverter produces exactly the same output voltage as an expensive huge 1500W one. But the 300W/120V one has an output current of only 2.5A and the 1500W/120V one has an output current of 12.5A. The 300W one uses cheap little transistors to switch only 30A from a 12V...
  20. audioguru2

    Power Supply 0-30V

    The long thread and other threads about fixing and improving the project disappeared when this site's data became corrupted. Here are the latest schematic and parts list:
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