Hi all - I’m noticing that many of the diy capacitor PCBs have a resistor, capacitor and LED on the output of the filter. Is the cap there for HF noise and the LED is just an indicator with a dropping resistor, or is there more going on? See pic below:
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The only legitimate reason would be as a bleeder resistor to discharge the capacitor in the event of no load. A resistor by itself would do this perfectly fine, I guess the LED is just eye candy.
The small yellow box capacitor is connected in parallel with the large cylindrical electrolytic capacitor. The little yellow guy is an attempt to "bypass" the large electrolytic cap at frequencies above the electrolytic's Self Resonant Frequency.
The resistor and LED are included simply to reassure the builder and/or service technician, that input voltage is present and is successfully rectified. "LED glowing" means "this piece is probably working correctly" so you can move on to other targets of troubleshooting.
(technical article #1)
(technical article #2)
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The resistor and LED are included simply to reassure the builder and/or service technician, that input voltage is present and is successfully rectified. "LED glowing" means "this piece is probably working correctly" so you can move on to other targets of troubleshooting.
(technical article #1)
(technical article #2)
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Is that resistor a 10K one or a 120 ohm one? I never know in which direction to read them.Hi all - I’m noticing that many of the diy capacitor PCBs have a resistor, capacitor and LED on the output of the filter. Is the cap there for HF noise and the LED is just an indicator with a dropping resistor, or is there more going on? See pic below:
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Not likely to be 120 Ohm as that would probably toast the led. Leds are also very bright these days. Less than 1mA is more than enough for the led to glow brightly. An easy to remember rule of thumb is to have 1k of resistance for every 1V of power supply voltage for the led resistor.
For me the led is an indicator for not only the power supply working but more importantly, that the capacitor is discharged before working on the equipment.
For me the led is an indicator for not only the power supply working but more importantly, that the capacitor is discharged before working on the equipment.