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  1. audioguru2

    Electronic Eavesdropping Devices Detector

    Hi Eplanet, In your personal message to me you say your circuit makes a continuous tone. As I explained, opamp A1 has a very high DC voltage gain and it amplifies its own input offset voltage. It is too bad that the circuit doesn't have an adjustment to cancel the offset voltage. A regulated...
  2. audioguru2

    guitar fuzz effect

    Hi Josh, Severe distortion produces fuzz. The diodes are in the negative feedback path of the opamp. The opamp will operate normally and will have a very high gain when its output level is less than about 1.2V peak-to-peak. When the output level tries to climb above 1.2V peak-to-peak then the...
  3. audioguru2

    Portable mic modification help

    Maybe the circuit needs a supply bypass capacitor to work from the AC adapter. Maybe the AC adapter is a switching type that has its switching oscillator producing the whistle. Maybe the adapter has poor filtering and produces hum that you say is a whistle.
  4. audioguru2

    12 V DC to a 220V AC Inverter AMplfier Design

    Pin 13 is an output and is not supposed to be connected to the supply. A high current would flow which might destroy it. Replace it. It is not a function generator IC. It is a common Cmos digital monostable/astable multivibrator that is made by most semiconductor manufacturers. Any square-wave...
  5. audioguru2

    Electronic Stethoscope

    Hi Steve, It is good to hear that it works well. ;D Hum is mains radiation picked up by the high gain input. Unshielded input cable usually causes it. If the wiring of your circuit is long like on a breadboard then it picks up mains hum. Use shielded audio cable from the microphone and keep...
  6. audioguru2

    500W 12v to 220v Inverter

    My schematic is correct. Check the pins numbers on your CD4047 carefully and if it doesn't work then replace it.
  7. audioguru2

    500W 12v to 220v Inverter

    Did you make the WRONG circuit or my corrected one? My corrected circuit was recently replaced by the wrong one. I don't know why.
  8. audioguru2

    Turning a 7805 on/off with a Push to Make Switch

    The CD4069 IC has a max operating voltage of 18V and the TIP125 darlington transistor has a max operating voltage of 60V so they are fine with only 13.4V. If your 7805 regulator has a current of 1A then it will try to dissipate 7.7W and it will probably get too hot and shut down unless it has a...
  9. audioguru2

    High Power LED Mood Lamp

    The same for the programming experts the author of this project Toon, and Kade who made some more programming changes and additions. In the author's forum, two other guys agree with my change of the base resistors but I have never been on that forum.
  10. audioguru2

    Automobile ignition power transistor

    Of course a power transistor in a hot car can fail. It won't gradually go bad, it will just stop working completely. All it does is switch on then switch off. A new one will perform exactly the same. Change the engine's air filter to get better performance.
  11. audioguru2

    Question about voltage.

    Wires connected to other wires don't discharge a battery. The voltage of the battery will remain the same because no energy is taken from it. A load connected across the terminals of a battery will discharge it and take energy from it. If a wire from one terminal of the battery touches a wire...
  12. audioguru2

    2 5V power source for a circuit

    The AC adapter jack probably has a switch in it to disconnect the USB when the adapter is plugged into it. Battery powered devices also have an adapter jack with a switch to disconnect the battery when the AC adapter is plugged into it.
  13. audioguru2

    High Power LED Mood Lamp

    Hi Nase, Welcome to our forum. ;D I noticed that you use 100 ohms base resistors for the transistors. Then the max output current rating of the PIC is is exceeded. Its absolute max output current rating is 25mA and yours is 43mA. Our project has the base resistors much to high at 10k. The author...
  14. audioguru2

    Electronic Eavesdropping Devices Detector

    Hi Eplanet, I think your project is working but you can't hear it. The opamps make a voltage-controlled-oscillator and your input voltage to them is 5V which is good. There should be a triangle wave at the output of A2 and the outputs of A3 and A4 should be a square wave. I think your...
  15. audioguru2

    dancing leds with counter

    The Dancing LEDs project has 10 LEDs that light one LED in a sequence. They step one LED for each sound that is picked up by the microphone. The Digital Step-km Counter project counts your steps and displays the number on a digital display. You said you wanted a Dancing LEDs circuit with a...
  16. audioguru2

    How easy to add Transmitter & Receiver Pair?

    They say data is transmitted and received. They say it must be programmed. I don't know how it does these things.
  17. audioguru2

    Question about voltage.

    The wiring in your house is "split" between all the outlets and lights. The voltage is the same at all of them. The wiring in your city is "split" between all the neighbourhoods. The voltage is the same at all of them. The same with your battery and millions of wires connected to it.
  18. audioguru2

    How easy to add Transmitter & Receiver Pair?

    The "typical application" schematic on the datasheet is too fuzzy to see how to connect it.
  19. audioguru2

    Electronic Eavesdropping Devices Detector

    Hi Eplanet, Welcome to our forum. ;D I fixed the schematic for this project. I did not check its pcb. Did you substitute any parts? Does your cell phone operate on a low microwave frequency? My cell phone uses some frequencies much higher than this circuit can detect. With a cell phone...
  20. audioguru2

    Turning a 7805 on/off with a Push to Make Switch

    I said: 1) The max current for a little 2N4403 is only 600mA. 2) The 10k base resistor for the 2N4403 limits its current to only about 150mA. 3) The CD4069 cannot drive a resistance lower than about 10k. 4) Use a darlington PNP transistor for higher current. You don't understand what? Do you...
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