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  1. Audioguru

    3 battery replacement supply?

    Cheap Chinese adapters have very poor voltage regulation. The Amazon overpriced adapter might not have a safety certification and might produce only 150mA (according to a user) then it might catch on fire if the LED string overloads it. The LED string is also from Amazon so it also does have a...
  2. Audioguru

    Once a minute chirp...

    Many years ago I built a few Neon Light Chasers powered by two 45V batteries. I cast each chaser in clear plastic. Then one blew up because I guess the battery gassed so I told the people with the others to get rid of them.
  3. Audioguru

    Trying to make a LDR circuit work ?

    My electrical utility company gave away compact fluorescent light bulbs for free to show people that they use much less power than incandescent. But many of them dripped flaming plastic because the Chinese manufacturer stole the certification label from a safe competitor so that those light...
  4. Audioguru

    Trying to make a LDR circuit work ?

    The Canadian government ordered the striking mail workers back to work then everybody received their Christmas gifts delivered on time and no cheap Chinese uncertified product blew up waiting in a mail truck.
  5. Audioguru

    Best soldering technique to prevent component heating?

    My Weller soldering iron temperature control uses a fixed temperature that is set buy the tip that is selected. More than 50 years ago I tried 600 degrees F, 700 and 800 but found the 700 degrees F ones work the best so I have used them ever since. It has lots of power so it heats up quickly and...
  6. Audioguru

    Best soldering technique to prevent component heating?

    Your cheapo soldering iron probably has no temperature control so it gets hotter and hotter which is too hot so that the tip oxidises and the rosin burns instead of cleans. Then you must overheat each solder joint and for too much time. My soldering iron is more than 50 years old and has...
  7. Audioguru

    Trying to make a LDR circuit work ?

    Why are most links to items posted on English language chat forums shown in foreign languages?? After clicking on the English button and getting the actual product's page but not the Home page like on most other sites, I see that the product is not certified to be safe and it will probably burn...
  8. Audioguru

    Trying to make a LDR circuit work ?

    Small cheap inverters are made to be powered from a 12V car battery (or your 12V battery) and they make 220VAC at 10W to 20W which will work fine to power a night light that you can purchase. But the inverter running 24 hours all day and night might drain your 12V battery too much.
  9. Audioguru

    Trying to make a LDR circuit work ?

    I think LDRs are so old and cheap that each one is different. Now the sun is low in the sky so is not very bright and I am measuring 1.6k on my LDR behind a double gazed window. Then the transistor will certainly be turned off. In the dark my LDR measures more than 10M (a little amount of light...
  10. Audioguru

    Trying to make a LDR circuit work ?

    My LDR measures 5.6k when the sky behind my window is very cloudy. 50k is not a standard resistor value, maybe you have 47k or 51k?. I calculated that your LED will turn off when the LDR is in sunshine. I suspect that you have the pins on your 2N2222 backwards since they have a different layout...
  11. Audioguru

    50w rms into 8 ohm load amplifier circuit using single dc power supply

    Websites "over there" have many circuits designed wrong. Maybe they use trial and error with many errors until it suddenly works"? Maybe good luck allows a circuit using parts that were selected at random instead of researched and of designing using the range of spec's? Maybe one circuit was...
  12. Audioguru

    50w rms into 8 ohm load amplifier circuit using single dc power supply

    The amplifier circuit was probably designed on a simulator where "typical" Vbe spec's are used without having an adjustment for minimum to maximum variations in the diodes. The simulation software ignores over-voltage and over-heating of the BC108 transistors and maybe the other transistors.
  13. Audioguru

    Audio limiter to quiet loud radio commercials

    A Jfet is used in many very low distortion sinewave generators to regulate the level. They use two resistors to feed half the level at the drain to the gate to reduce the distortion. If the level at the drain is 50mV peak then the distortion is very low. If the level at the drain is 100mV peak...
  14. Audioguru

    Audio limiter to quiet loud radio commercials

    He wants passive circuit without a power supply or opamps so it will have many problems reducing (actually muting) loud sounds. The input signal probably has a level that is too low for a passive circuit. Some compressor circuits use an active fullwave rectifier to sense then reduce levels.
  15. Audioguru

    50w rms into 8 ohm load amplifier circuit using single dc power supply

    Do not try making an audio amplifier posted on a website (Circuits Today) in India that uses antique BC108 transistors that have a supply voltage that is much too high for them. I did not check if all the other transistors will work in that old circuit and if they are also antique. The value of...
  16. Audioguru

    Audio limiter to quiet loud radio commercials

    The way to fix the N-channel Jfet circuit is to bias the source to about +5V or more and have the gate voltage zero when the audio input level is low and the rectified audio makes +5V or more to turn on the Jfet which reduces the output level when the input level is loud.
  17. Audioguru

    Audio limiter to quiet loud radio commercials

    Wait a minute. With the source of the N-channel Jfet grounded and the diode bridge making a negative gate voltage for it when the input audio gets too loud then the output audio will get louder, not quieter.
  18. Audioguru

    Audio limiter to quiet loud radio commercials

    Since you are using an N-channel Jfet as an on-off switch and not as a linear attenuator with automatic level control then the Jfet source can be grounded and the diode bridge creates a negative voltage to the Jfet gate to reduce the conduction of the Jfet for maximum output level of the audio...
  19. Audioguru

    Charge time for lithium batteries

    A kid on my street has a skateboard that powers him up the hill. Its lithium battery and motor are very small and can barely be seen. He charges it each night and rides it to school every day. Other kids carry their unpowered skateboard up the hill.
  20. Audioguru

    Audio limiter to quiet loud radio commercials

    4 diodes are never used to rectify audio, an active rectifier circuit with an opamp is used to cancel the diodes forward voltage drop. The rectifier circuit produces a positive voltage when the audio level is loud and is 0V when the audio level must not be reduced.The N-channel Jfet conducts and...
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