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  1. audioguru2

    Wired Headset Intercom

    The headset mic is probably an electret type that has a Jfet transistor inside THAT MUST BE POWERED. The LM386 circuit does not power it so you must add one 1k series resistor from the +9V and one 100uF capacitor to ground to filter the supply voltage and add a second series 10k resistor from...
  2. audioguru2

    Wired Headset Intercom

    Your block diagram shows a "telephone?" handset and some headphones with mics. You need to know which type are the mics (carbon, electret, dynamic or piezo) for a circuit to work properly with them. Then the inputs of the LM386 modules need to have the proper parts added for them. The LM386...
  3. audioguru2

    6V lead acid battery

    A lead-acid battery remembers that it has been killed by an over-discharge. It should NEVER be discharged to less than about 5.5V for a 6V battery but some "deep discharge" batteries might survive a lower voltage. Your battery might have its lead plates "sulphated" or the plates might have...
  4. audioguru2

    1-25 volt power supply

    Its voltage gain is only 1 so you cannot use an accurate 2.5V reference and produce a 25V output. Therefore the voltage gain was made to be 10.
  5. audioguru2

    1-25 volt power supply

    The last schematic has a voltage gain of 10. But many opamps have inputs that cannot go as low as zero voltage without having a negative supply.
  6. audioguru2

    i need help for designing a circuit gives 20 mA output using battery source

    Then Ohm's Law says that the constant current source needs to produce a voltage of (1k x 20mA=) 20V to (5k x 20mA=) 100V. Where will you find a battery that is 100V when it is almost dead?
  7. audioguru2

    i need help for designing a circuit gives 20 mA output using battery source

    You did not ask for constant current as the battery voltage runs down or when the load resistance is changed. If you use a 9V battery that actually measures 9.0V then a load resistance of (9V/20mA=) 450 ohms draws 20.0mA. There are many constant current source circuits in Google. Most use an...
  8. audioguru2

    Micro USB battery charger and 3.3V supply

    Why is your schematic an awful looking negative image?? admin: please be polite The 3.3V regulator will stop working long before the battery voltage drops to 3.2V. What will prevent the battery voltage from being discharged too low? You need a protection circuit that disconnects the load on...
  9. audioguru2

    0-30V Stabilized Power Supply

    Oh. Do you have a very inductive shunt on a current meter in series with the output of this power supply? Or maybe R7 is inductive?
  10. audioguru2

    0-30V Stabilized Power Supply

    Hi Redwire. When the power is turned off, I do not see how the output can swing to +61V then to -65V. It is ringing at about 4MHz.
  11. audioguru2

    building Hi-fi speakers

    Here is an excellent site for articles and projects about audio: http://www.sound.westhost.com/index2.html 
  12. audioguru2

    Energy Plug Meter

    I can "rent" an energy meter for two weeks for free from a local library. But I never tried one because here electricity is inexpensive.
  13. audioguru2

    power supply

    Will your teacher let you copy the very good but extremely simple 5V voltage regulator circuit shown on the datasheet of a uA7805 voltage regulator integrated circuit? The datasheet shows the circuit and lists its accuracy and its maximum output current.
  14. audioguru2

    power supply

    All the details of your school assignment are missing: 1) How much output voltage? 2) How much maximum output current? You cannot design a simple power supply without knowing these basic things.
  15. audioguru2

    0-30V Stabilized Power Supply

    I suspect that the noise comes from the 5.6V Zener diode voltage reference. If it has a bypass capacitor then I hope that opamp U1 does not oscillate. Another reason to use a REAL voltage reference.
  16. audioguru2

    It's quiet in here

    Since there is new forum software I am busy counting how many times a new spammer can post the same spam over and over and over and over ....
  17. audioguru2

    1-25 volt power supply

    No Kevin. The voltage reference IC is 2.5V. Then for 25.0V output the gain must be exactly 10, not 100 and not 10,000.
  18. audioguru2

    0-30V Stabilized Power Supply

    Your schematic is missing a temperature sensor and parts for the opamp.
  19. audioguru2

    1-25 volt power supply

    If the darlington output transistor was not included in the negative feedback loop of the opamp then its output voltage world drop about 1.4V when the load current is increased from almost nothing to 1.5A. The current limiter reduces the output voltage an additional 0.7V for a total reduction of...
  20. audioguru2

    0-30V Stabilized Power Supply

    Texas instruments invented the TIP3055 transistor and their datasheet says the collector pin is connected to the heatsink tab. But ST Micro copied it and their datasheet does not say anything about the `live` heatsink tab.
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