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  1. audioguru2

    Can a NiMH battery be charged by a NiCad charger?

    That is correct, the Ni-MH cells will charge fine, but take longer for a full charge. Compare the mA/hr rating of the different types to determine how much longer. Some old AA Ni-Cads were rated at only 500mA/Hrs. New Ni-MH cells have 5 times that capacity so will take 5 times longer to fully...
  2. audioguru2

    Electronic Stethoscope

    To avoid shorting outputs together and avoid a switch, you need an audio mixer circuit. You can use electronic switches like Cmos transmission gates, or an audio mixer circuit. In order to keep the LM386 and a volume control from overloading, the volume control is always ahead of the amplifier.
  3. audioguru2

    Bass Box

    Hi Mukhalled, The LM2005 amp doesn't have enough power for your 6 ohm bass box. It will be only about 10W at clipping when its amps are bridged. The preamp has low impedance outputs therefore can drive many amplifiers. Use a 10k resistor from each output of the preamp to the capacitor at the...
  4. audioguru2

    Electronic Stethoscope

    The output level from the output of the LM386 is about 200 times too high for a mic input! Right before the volume control is about 10 times too high for a mic input. These signal levels are speaker level and line level, not mic level. An attenuator is needed to connect them to a mic input. The...
  5. audioguru2

    Electronic Stethoscope

    It sounds pretty good except for the extra noises. I don't hear much hiss (air noise?) in your recording. The extra noises are friction of the mic holder on the skin, or friction of the cable moving. It could also be noises caused by loose connections on your breadboard.
  6. audioguru2

    0-30 Vdc Stabilized Power Supply

    Leave R7 at 0.47 ohms. 3A through 0.47 ohms makes a voltage drop of 1.41V. If the meter is 200mV full-scale then it needs an attenuator. If the internal resistance of the voltmeter plus its series calibration resistor is only 47 ohms or less then the calibration will be affected.
  7. audioguru2

    0-30 Vdc Stabilized Power Supply

    A shunt resistor in series with the output of the project ruins its fantastic voltage regulation. Just switch the voltmeter to read the voltage across R7, which is the load's current.
  8. audioguru2

    3-5V DC @50mA from 230V AC without transformer

    The text in the 1st one says it is not efficient and is not safe. The 2nd circuit is the same.
  9. audioguru2

    Can a NiMH battery be charged by a NiCad charger?

    If the charger is a "fast" one for Ni-Cads then it will probably overcharge Ni-MH cells because of the difference that occurs when they are fully charged. Fast charging is 4 hours or less. Fast overcharging results in venting or in an explosion. If the charger is designed to charge overnight...
  10. audioguru2

    JRC 8 Pin Dip ???

    Hi Zap, Most manufacturers make the NE5532 and the "D" package is a tiny surface-mount one, not DIL. Usually I look at www.datasheetarchive.com for datasheets but this one I found in Google: http://www.semiconductors.philips.com/acrobat/datasheets/NE_SE5532_A_SA5532_3.pdf
  11. audioguru2

    Some kind of RPM counter

    Your white LED is really a blue one with a yellowish phosphor, and doesn't match your phototransistor's color response very well. It can be made much more sensitive: 1) The phototransistor can be made more sensitive by increasing the value of R4. The resistor at pin 2 should also be increased...
  12. audioguru2

    Bass Box

  13. audioguru2

    IR receiver

    Does your TSOP1738 have the recommended 4.7uF supply bypass capacitor?
  14. audioguru2

    Bass Box

    Hi Mukhalled, The amp must match your bass box's speaker or speakers. How many bass speakers and what is their impedance? How much true power do you want? Many amp circuits would be suitable if they operate well in the temperature extremes of a car. The problem you will have is making a supply...
  15. audioguru2

    best voltage and current regulator

    If your LED has a forward voltage drop of 1.8V and you connect it to two AA cells in series (3V) without a current-limiting resistor then the extra 1.2V would create a current that is so high that the LED would instantly burn-out! You don't say the color of the LED that determines its voltage...
  16. audioguru2

    best voltage and current regulator

    Please attach a schematic of your circuit. I don't understand how your LEDs can burn-out. A red LED has a forward voltage drop of about 1.8V. Most LEDs have a max current rating of 30mA. If you have a 100 ohm current-limiting resistor in series with it then 4.5V across the combination results...
  17. audioguru2

    Sound Level Indicator

    Hi Giroup, Why don't you make my Sound Level Indicator project? http://www.electronics-lab.com/projects/motor_light/009/index.html I used 20 very bright red LEDs but it would also look good with ultra-bright blue or green only 10 LEDs.
  18. audioguru2

    6V LED Chaser Question

    Hi Giroup, I make most of my circuits on Veroboard which is also called Stripboard. What color are your LEDs? I find that ultra-bright blue and green ones look the most spectacular. At night, they light up the house across my wide street.
  19. audioguru2

    need help finding report information

    It is a very simple circuit. You would need to learn about how transistors work in order to understand the functions of its few parts.
  20. audioguru2

    Lowpass filter for subwoofer

    The pcb and the parts shown on it are correct, but I think the LED is shown backwards. The schematic and parts list are incorrect. Use a preamp that has a low output impedance.
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