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  1. audioguru2

    Electronic Stethoscope

    Hi May, I think that the low frequency response and seal of the headphones determines the experimental result of this project. I tried pretty-good cover-the-ears headphones and heard my heartbeat loud and clear. Then I tried a pretty-good speaker and after turning down the volume to avoid...
  2. audioguru2

    Car touch sensor!

    Of course it won't work with its input shorted to the positive supply.
  3. audioguru2

    best voltage and current regulator

    You shouldn't connect LEDs in parallel. Their forward voltages will be slightly different causing the one with the lowest voltage to hog all the current and maybe burn out. Each LED should have its own current-limiting resistor. In my 3V Ultra-bright LED Chaser project I use a Schmitt trigger...
  4. audioguru2

    Input signal for LM3915. need help.

    In the BAR mode, an LED will remain lighted when the sound level is reached and is exceeded. The current in the detected LED can still be detected with an optical isolator. The battery won't last very long when many LEDs light in the BAR mode.
  5. audioguru2

    Input signal for LM3915. need help.

    You need to detect when an LED blinks, since your LM3915 is in the DOT mode. A logic gate or a comparator isn't needed. The LED to be detected operates with current, not voltage. The LED of an optical-coupler could be connected in series with the LED to be detected and its phototransistor could...
  6. audioguru2

    need help finding report information

    You have opened 3 topics about the same circuit. You posted the schematic and parts list in this topic: http://www.electronics-lab.com/forum/index.php?topic=5970.msg36817#msg36817 Please keep in the same topic by replying to it without opening a new topic each time. Does the circuit work? What...
  7. audioguru2

    Lowpass filter for subwoofer

    In the project, there is a link to a discussion about this confusing project. Last year, I wrote this about it: "I see, the pcb has more parts than the schematic: 1) Two 4.7uF/35V bypass caps in parallel with C2 and C6. 2) An LED (isn't it backwards?) and 1.5K current-limiting resistor at the...
  8. audioguru2

    Car touch sensor!

    The circuits are exactly the same when you remove the short of the sensor plate to the battery in the 1st one. It won't work if you get close to the sensor plate. It works when the resistance of your body completes a connection from the sensor plate to the negative battery terminal.
  9. audioguru2

    Input signal for LM3915. need help.

    Why use a logic gate? It wasn't gating anything.
  10. audioguru2

    Phototransistor circuit

    Hi Staigen, Your post wasn't deleted. Jumbo posted his question on 3 different forums here and you and I are answering him on different forums. I think the moderators should combine all posts that are the same. While they are at it, the moderators should get rid of the guy who is selling his...
  11. audioguru2

    200W Audio amp by kemo kits

    Hi Silicon, That project should use TDA2030A ICs that have an absolute max supply voltage of 44V. The project's supply will produce 42V without being driven hard. There is no way that the amp will produce 200W. 200W into 4 ohms is a peak-to-peak voltage swing of 80V. At such a high current, the...
  12. audioguru2

    Problem Connecting to Site

    It is a nightmare, isn't it? Many of us have trouble connecting to this site frequently, for many hours, then it suddenly starts working fine again.
  13. audioguru2

    9V power source

    You didn't post your project's schematic so we can't see what supply voltage its parts need. Will the parts work from the 2.0V to 3.0V from a couple of battery cells?
  14. audioguru2

    Greetings from Ottawa

    Hi Ante, This site frequently goes down for many hours. It doesn't bother me anymore, I just go to other electronics forums.
  15. audioguru2

    0-30 Vdc Stabilized Power Supply

    The 2N6036 is a PNP type which is expensive and is not recommended for new designs so might not be made anymore. I recommend a TIP-110 NPN darlington transistor that is made by many companies.
  16. audioguru2

    Electronic Stethoscope

    The -3dB (half-power) highpass cutoff frequency of a capacitor and a series resistor is at the frequency where the reactance of the capacitor equals the value of the resistor. C1 is in series with R2, which is also in series with the impedance of the mic (about 5k) in parallel with R1. So the...
  17. audioguru2

    Input signal for LM3915. need help.

    Good. The datasheet says that the resistance at Rhi is typically 28k. You can measure the voltage of Rhi or calculate it. With a 5V reference and 20k in series with the 28k, the Rhi voltage is 2.92V. Using 220k, the Rhi voltage is 0.57V. The voltage reference pin of the LM3915
  18. audioguru2

    Car touch sensor!

    Hi Um, Your idea of having the entire car as a touch sensor has problems: 1) Most touch sensors detect the effect of the 100pF of a human on a high frequency oscillator. The oscillator and the human are referenced to EARTH. So your circuit will need to have a ground strap under the car. 2) Most...
  19. audioguru2

    Electronic Stethoscope

    Correct. Energizer's site used to have more detail about their batteries but still show how quickly the six AAAA cells inside a little 9V alkaline cell drop in voltage with current.
  20. audioguru2

    6V LED Chaser Question

    Hi Giroup, It looks good. ;D
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