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  1. audioguru2

    Constant current battery charger

    The battery voltage will rise to about 14V when fully charged but the LM317 current regulator needs a voltage across the LM317 of at least 2V plus 1.25V for the current-setting resistor so you need an input of at least 17.25V. Since your input voltage is too low then your battery will never be...
  2. audioguru2

    0-30V Stabilized Power Supply

    Thanks, Dracu. I saved them.
  3. audioguru2

    0-30V Stabilized Power Supply

    Heatsinks that are made by heatsink manufacturers have datasheets that detail their "thermal resistance" spec'd so you can calculate the chip temperature of the transistor at various dissipations. They are usually anodized black to radiate heat better.
  4. audioguru2

    0-30V Stabilized Power Supply

    Hi Mendimano, Your transformer is 30V when at its max rated load. Then its peak voltage is 42.4V and the bridge rectifier drops it to 40.4V. The ripple in the filter capacitor drops it to 39.4V. The voltage across R7 is 1.35V and the voltage across each 0.33 ohm emitter resistor for the output...
  5. audioguru2

    0-30V Stabilized Power Supply

    We have posted the latest circuit and parts list millions of times on these forums.
  6. audioguru2

    0-30V Stabilized Power Supply

    Hi Dracu, I am glad to hear that your psu works fine. ;D R22 dissipated almost 1/2W when the transformer was 30VAC and the 10V zener diode was not installed. Now it can be a little 1/4W resistor. It is easy to calculate the power in a resistor. The 0.33 ohm emitter resistors have a max current...
  7. audioguru2

    0-30 Vdc Stabilized Power Supply

    But the output of the project with a transformer that is only 24VAC is only about 25V at 3A, not 30V. The opamps in the original project have a supply voltage that is higher than their max allowed voltage. 28V and 30V transformer are common in Canada and the US. Maybe also in europe. 44V opamps...
  8. audioguru2

    BH1417F VCO Tuning Issues

    I think the BH141x ICs are designed for four low frequencies or four high frequencies. So you must re-adjust the tuned circuit to have one or the other.
  9. audioguru2

    Balance Microphone amplifier

    Is the problem caused by echoes in the room or is it caused by some voices are too loud and other voices are too soft? It is a stupid idea to use a mic mounted on the ceiling to pickup voices in the room. Maybe it would work if the room has no echoes because it has acousic tiles on the ceiling...
  10. audioguru2

    Car battery circuit design - comments, feedback?

    Your latest circuit will work but the transistors should not be "emitter-followers". Instead they should be common-emitter for less voltage loss.
  11. audioguru2

    Car battery circuit design - comments, feedback?

    Now your circuit will work properly. The hysteresis resistor is a high value. Try 1M.
  12. audioguru2

    Car battery circuit design - comments, feedback?

    The "input common mode voltage range" of an opamp or comparator is the range of voltages that the inputs still work. The max common mode input voltage for an LM339 quad comparator or an LM393 dual comparator is 1.5V less than its positive supply voltage (the same as the LM311 comparator) so...
  13. audioguru2

    Car battery circuit design - comments, feedback?

    With the capacitor in series with the two resistors then your circuit does not have a reference voltage. The input is at +15V. Usually a reference voltage is a regulated voltage. The LM311 will not work with its inputs so close to its positive supply voltage because its inputs have a typical...
  14. audioguru2

    Balance Microphone amplifier

    A microphone that is in a room that has echoes is supposed to be 0.05m to 0.3m from the person's mouth. 2-3m is much too far away especially when it is pointing at the top of the doctor's head instead of at his mouth. More loudness and AGC will probably amplify the echoes exactly as much as the...
  15. audioguru2

    My First Post And First Question

    Welcome and good luck with your exam. You can buy a "single throw" (2 terminals) toggle switch that simply turns something on and off. Or you can buy a "double throw" toggle switch (3 terminals) that turns on lamp #1 and turns off lamp #2 in one toggle direction then turns on lamp #2 and turns...
  16. audioguru2

    Balance Microphone amplifier

    Hi Shahriar, The mic is probably an electret type, not a condenser type. Some people call it an electret condenser mic. If shielded audio cable is used then the distance of only 12m is fine and the shield will prevent mains hum pickup. If the mic is now connected with a twisted pair of wires...
  17. audioguru2

    Dual battery Dual charger board with IO monitor output

    Kevin, Don't you know that 120VAC is used only in the US, Canada, Mexico and a couple of other countries. 230VAC is used in the remaining hundreds of countries all over the world.
  18. audioguru2

    zener diodes

    A voltage regulator needs to have a voltage reference. Low voltage and adjustable voltage regulator ICs use a "band-gap" circuit. Higher voltage regulator ICs use a zener diode. Voltage regulators have a power error amplifier that supplies power to the load, not the little low current zener diode.
  19. audioguru2

    Amplification and loss

    It is desirable for an audio amplifier to have extremely low distortion. Then it has a very high open-loop gain and uses plenty of negative feedback to reduce the gain to a useable amount and the negative feedback reduces the already fairly low distortion. If you attenuate a signal so that an...
  20. audioguru2

    0-30V Stabilized Power Supply

    I always design circuits so that any transistor that meets the minimum or maximum spec's works fine. Are you designing the circuit so it only works with the transistors you measured then it might not work if a transistor is replaced? The minimum hFE is 20 at 4A. The datasheet has a typical...
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