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  1. audioguru2

    Help with Homeschooling (make me a hero)

    Certainly, if the rectifier has a transistor switch and a strong battery in it. ;D
  2. audioguru2

    Convert 0-30V 3A PSU to 5A or more

    A good way to blowup stuff. Without the transistors then the feedback will normally force the output high. That is normal. It is probably OK. It is used only for a moment when the power is turned off.
  3. audioguru2

    IR receiver

    A supply bypass capacitor: 1) It is a current resevoir. It supplies very high momentary current to the circuit when needed. Very useful with a battery that has its internal resistance rising as it runs down. 2) It is a low impedance at high frequencies to stop amplifiers from oscillating and to...
  4. audioguru2

    battery charger

    The 220 ohm resistor has 1.2V across it and its current is in the pot for the LM317 to have a variable regulated output voltage. Look at the datasheet for the LM317. The diode isn't needed. It protects the LM317 from the output capacitor discharging into its output in the very unlikely event of...
  5. audioguru2

    Resistance and Resistivity

    If the input voltage and the load's current never change (they nearly always change) then simply use Ohm's Law to calculate the resistance.
  6. audioguru2

    battery charger

    The 7805 has 5V between its OUT and GND terminals. So if you have the 10 ohm resistor in series with the 100 ohm pot at max, 5V/110 ohms= 45.5mA. With the pot at minimum, 5V/10 ohms= 500mA. If the GND terminal is grounded, then the output is a regulated 5V with up to 1.5A.
  7. audioguru2

    Convert 0-30V 3A PSU to 5A or more

    Oh, oh. If Q2 has a pretty good heatsink then it should be fine. If the three 2N3055 transistors have minimum gain of 32 at 7A/3, their total base current is only 219mA. Q2 will have about 39.2V across it when the output voltage is 2V so dissipates only 8.6W. With a "perfect" heatsink a TIP31A...
  8. audioguru2

    500W 12v to 220v Inverter

    Some people think that the 0.1 ohm resistors aren't required. I think that the strongest transistor will hog the load without them and burn out. Do you want to try the circuit without them? The 100 ohm resistors' value is not critical. 33 ohms to 1k will work. I don't know.
  9. audioguru2

    common-mode??

    Hi Ron, It is about time that you came over to this web-forum. ;D
  10. audioguru2

    VHF AMPLIFIER (PLZ ANSWER)

    Is 86-108MHz the "frequency of catering" for the project?
  11. audioguru2

    Input signal for LM3915. need help.

    Sure, your picis fast enough to check the level of an average-detected and rectified signal.
  12. audioguru2

    Help with Homeschooling (make me a hero)

    The specs show an operating current of 2uA tp 6uA for their accellerometers, which is what I assume that you have. The specs show that the 1M ohm of the input of an oscilloscope loads-down the extremely high output impedance of a piezo sensor. High impedance means very low output current. Did...
  13. audioguru2

    Help with Homeschooling (make me a hero)

    The spec's mention an output current of only 2uA to 6uA for the piezo sensor. An LED uses an operating current that is 1000 times more.
  14. audioguru2

    Help with Homeschooling (make me a hero)

    IF the piezo is big enough and you hit it hard enough, the LED will blink. I don't think it is big enough to charge a big capacitor to continuously light an LED.
  15. audioguru2

    charger for Cordless phone battery.

    Yes, if the battery is rated for 300mA/hrs. No. 7V is too low. "The  minimum input voltage to the circuit is 7.75V."
  16. audioguru2

    charger for Cordless phone battery.

    I don't know where you learned the wrong voltage formula. Each cell will charge to 1.4V to 1.5V. Therefore the 3-cell battery will be 4.2V to 4.5V when fully charged. The LM3117 needs at least 2V across it and the current-sensing resistor has a 1.25V drop, so the minimum input voltage to the...
  17. audioguru2

    IR receiver

    All electronic circuits work better with a supply bypass capacitor. It is a current resevoir and a very low impedance at high frequencies and keeps amplifying circuits from oscillating and from bouncing around.
  18. audioguru2

    PC Oscilloscope"need help"

    The microphone input of a sound card is designed for a signal not exceeding 100mV and gives a bias current for an electret mic. The line level is designed for maybe a max of plus and minus 5V, check the spec's for your sound card.
  19. audioguru2

    500W 12v to 220v Inverter

  20. audioguru2

    500W 12v to 220v Inverter

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