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  1. Audioguru

    Peak detector to A/D of PIC

    The capacitor is charged slowly through the high values of your 20k to 10k voltage divider. An opamp would charge the capacitor mat least 100 times faster. You do not want a simple voltage follower, instead you want a precision peak detector with the diode voltage drop cancelled because it is...
  2. Audioguru

    Peak detector to A/D of PIC

    Of course the output from the peak detector will be gone if it is loaded with 5k ohms or less. Usually an opamp is used for a peak detector because it has a low output impedance.
  3. Audioguru

    What are these 2 "extra" red wires for? Li-Ion RC Battery

    The battery has three Li-PO cells. It is 12.6V when fully charged and averages 11.1V during a discharge. The 4 wires plug into a balanced charger with a wire for each cell plus a common 0V wire. The two wire plug is its high power output. A balanced charger prevents each cell from overcharging...
  4. Audioguru

    Peak detector to A/D of PIC

    What is the peak voltage of the pulse? 333uV? The resistors R1 and R2 reduce it to 100uV that feed the diode but the diode has a voltage drop of 600000uV so its output is zero. Amplify the pulse signal a few thousand times then use an active precision peak detector circuit that cancels the diode...
  5. Audioguru

    Fixing Technics Speaker

    Isn't Technics a Panasonic international company? Then why don't they speeky zee Engrish and not say "high tone" and "low tone" for the tweeter and woofer? I suspect that many customers connected the tweeter where the woofer should go and blow up the tweeter and/or amplifier.
  6. Audioguru

    Power supply !!

    Isn't it amazing that some countries are so "backwards"? Like another world.
  7. Audioguru

    Ultrasonic sonar

    Why do you have a capacitor parallel to R4?
  8. Audioguru

    Ultrasonic sonar

    Your opamp is not powered and it is not biased so it will probably do nothing. Usually the input of an opamp used as an amplifier is biased at half the supply voltage and has an input coupling capacitor that your circuit has. Then the output can swing up to almost the supply voltage and down to...
  9. Audioguru

    Ultrasonic sonar

    A pretty good opamp runs out of voltage gain at 10MHz. Then at 40kHz its gain without AC negative feedback is 100 which might not be enough. So use two opamps in series, each with a gain of 15 or 20.
  10. Audioguru

    Power supply !!

    Some of the parts in the old power supply schematic are older than his country of Algeria that did not exist when I went to school so I looked it up. It has an intriguing history of Arabia and France ruling it with wars and pirates.
  11. Audioguru

    Ultrasonic sonar

    Are you using the receiving opamp as a comparator? It should have some hysteresis. Many opamps do not work well at 40kHz, use a comparator instead.
  12. Audioguru

    Power supply !!

    Your transistors are extremely old and have been obsolete and not made for many years, except the 2N3055. The transformer output is 24VAC which produces a rectified and filter DC output of 32V which is much too high for a 20V power supply. The main filter capacitor value of 47uF is much too low...
  13. Audioguru

    Op amp LM339 help

    Aren't you measuring the +2.5V output with a slow voltmeter? Try looking at it with an oscilloscope to see the high frequency squarewave switching from 0V to 5V over and over.
  14. Audioguru

    Op amp LM339 help

    "The output goes to 5 volts with a separate 0-2.5 volt dc signal" but the output does not go high enough "when connected to the unit I’m trying to interface with". Then whatever drives its input with 0V to 2.5V is probably modulating its voltage on and off so that the average voltage at the...
  15. Audioguru

    MOSFET burning up but similar circuit on another board is fine

    The replacement IRL540L has a maximum on-resistance of 0.077 ohms when its Vgs is 5V. But the original STP22NE10l is worse at 0.1 ohms. But the original circuit might have used Mosfets selected (or survived) to be the best ones with a much lower on resistance.
  16. Audioguru

    LTC1050 to NJM2904D circuit

    I have never used a Cmos opamp.
  17. Audioguru

    LTC1050 to NJM2904D circuit

    No, most of those opmps will not work in this circuit since their inputs do nothing if they are within a few volts from the negative supply voltage, requiring re-biasing or an additional negative supply. Also, the first opamps listed, the TL07x and TL08x have a problem called "Opamp Input Phase...
  18. Audioguru

    Led stair lights with 2 motion sensor. circuit help!

    I do not know if a passive IR detector will detect heat from the LEDs that light the stairs.
  19. Audioguru

    LTC1050 to NJM2904D circuit

    The LTC1050 single opamp has Jfet inputs so it has almost no input bias current, then the photodiode is very sensitive to low light levels. But the NJM2904 dual opamp is the same as an LM358 or LM2904 dual opamp that has a fairly high input bias current that pulls the inverting input high...
  20. Audioguru

    I'm getting there, slowly

    I am sorry to hear that your power supply died from drinking too much beer and got alcohol poisoning. I had a dog that drank my beer when I had it in a mug, but since changing to beer in cans my dog couldn't "bottom up" it.
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