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  1. Audioguru

    JVC Speaker getting power but not producing sound

    Inside the speaker cabinet, measure the resistance of the speakers, and any crossover coils. I found two large Sony speakers on the curb (thrown away as garbage). They have 10" woofers with small magnets and the cheapest looking 3" "tweeters" I have ever seen. The tweeters were burnt out. My...
  2. Audioguru

    I have a question about a fan I built using a dc motor.

    Little kids are taught about the dangers of 120AC from their parents and at school. They are taught to never plug in something that should not be plugged in to the electricity. Electrical engineers are taught everything about electricity before they fiddle with it. I am glad that you did not...
  3. Audioguru

    How to connect op amps in parallel

    In the United States your circuit is feeding the entire country's electricity grid. You need the power from millions of paralleled opamps to drive it. If you add a series inductor to isolate your electricity line at each end then you will need the power only from hundreds of opamps. Is your...
  4. Audioguru

    I have a question about a fan I built using a dc motor.

    You said that the motor in the clipper ran from batteries. Didn't you see the batteries and count them? If you did then you will know the voltage rating of the motor. You asked of you can try plugging it into a 120VAC wall outlet. But batteries are low voltage and are DC, not AC. The voltage...
  5. Audioguru

    Load resistor for 12V battery

    Use Ohm's Law to calculate the value and power rating of the resistor. But the battery voltage runs down as it is discharging so pick an average voltage of about 13V. 13V/1A= 13 ohms which is not a standard value, use 12 ohms and the average current will be 13V/12 ohms= 1.0833A. When the battery...
  6. Audioguru

    LED Circuit Help.

    I hope your adapter has a DC output but you call it an AC adapter instead of calling it an AC to DC adapter. If its output is not regulated then without a load its output will be higher than it is rated. If it is regulated then its output will be about within 5% from 12V (11.4VDC to 12.6VDC). So...
  7. Audioguru

    Math Question, How Do You Really Figure This Out

    In real life it might quickly burn out or not light. The datasheet is supposed to say its minimum and maximum voltages so that you can design your circuit to use it properly.
  8. Audioguru

    LED Circuit Help.

    LEDs are not rated for 2V. They could be anywhere in the range from 1.7V to 2.2V. If all your LEDs have the minimum forward voltage of 1.7V and you apply 2.0V then POOF the LEDs are gone. If they are all 2.2V and you apply 2.0V then they will not light or they will be very dim. You must limit...
  9. Audioguru

    LED Circuit Help.

    An LED is driven from current not voltage. Most 5mm diameter LEDs are used at 20mA. Leds have a range of voltage because they cannot be made to be the same so if you connect a 1.8V LED to a 2V power supply then it will soon burn out because the current will be very high without a resistor to...
  10. Audioguru

    Math Question, How Do You Really Figure This Out

    Since you have only 1 LED then you must have measured its forward voltage so that if it is minimum then it does not burn out and if it is maximum then it is not too dim. Temperature change causes a tiny variance, its wide range of possible forward voltage is a huge variance.
  11. Audioguru

    Capacitor In Line?

    If the capacitor value is too low then the DC will have a lot of AC ripple voltage on it that reduces the average voltage. With no capacitor then the average voltage after the rectifier bridge is about 14.9V. The peaks will be about 23.5V. In between the peaks the voltage will be 0V.
  12. Audioguru

    Is the microphone input on a mixer a normally closed circuit?

    The switch must be connected with shielded microphone cable. The switch should have gold plated contacts (it costs the same as high current silver contacts) because when the silver tarnishes then it will not short a mic signal.
  13. Audioguru

    Need relay that operates with 3.8 VDC input.

    The datasheet for every relay shows its minimum pull-in voltage. I haven't used a relay for about 45 years so I cannot remember if it is a certain ratio of its nominal voltage.
  14. Audioguru

    Math Question, How Do You Really Figure This Out

    Did you measure the forward voltage of your LEDs and group them into matched sets? Then did you calculate a different resistor value for each set?
  15. Audioguru

    Battery charged by a solar panel?

    That is a nice charging module. I wonder if it is "prime" or is a reject from a manufacturer. I guess you will get your money back if it doesn't work properly and you pay more than its cost to ship it back to China.
  16. Audioguru

    Math Question, How Do You Really Figure This Out

    When I buy LEDs their forward voltages do not match. But when I found strings of Chinese LEDs (powered from 4.5VDC) they are all in parallel and the forward voltage matched. Even the series-connected outdoors blue LEDs matched pretty well. Even my cheap Chinese flashlight has 24 well-matched...
  17. Audioguru

    I need help,AC/AC power transformer,please take time and read...

    Heatsinks are made in many sizes.
  18. Audioguru

    I need help,AC/AC power transformer,please take time and read...

    The problem is that some power supplies are labelled 5V but produce up to 9V which is too high for my circuit. I have a cheap power supply rated at 9V that produces 19V into a low current load. It gets hot even if it has no load.
  19. Audioguru

    I need help,AC/AC power transformer,please take time and read...

    I have a box full of AC-DC wall plug power supplies. I am looking for 5VDC at 350mA and found a few that are labelled 5V at 500mA, 1A and 2A. Most have a voltage that is about 6V to 9V at 350mA. I found a 5V one but its cord is too stiff. I used one that is 5.2V and it has a long flexible cord.
  20. Audioguru

    Math Question, How Do You Really Figure This Out

    Or you can buy thousands of LEDs, then measure them all and sort them into piles that have similar voltages. Many Chinese LED products doo dat.
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