Capacitance needed to stabilize a voltage pulse

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Discussion Overview

The discussion revolves around determining the appropriate capacitance value needed to stabilize a voltage pulse for powering a small LED. The context includes considerations of pulse voltage characteristics, load requirements, and circuit parameters.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant inquires about the value of a capacitor needed to stabilize a 6mV pulse voltage for an LED.
  • Another participant argues that 6mV is insufficient to power an LED, which typically requires around 20mA at a higher voltage.
  • A suggestion is made that the original poster might have meant a 6V pulse instead of 6mV, referencing a previous thread for clarification.
  • It is noted that the capacitance required depends on factors such as pulse frequency, duration, load resistance, and desired stabilization level.
  • A participant mentions that the time constant of the circuit, which is the product of capacitance and load resistance, should be significantly larger than the pulse duration for effective stabilization.
  • Recommendations are made to consider capacitor types with low equivalent series resistance (ESR) and high capacitance stability for optimal performance.

Areas of Agreement / Disagreement

Participants express disagreement regarding the sufficiency of a 6mV pulse to power an LED, with some suggesting a possible misunderstanding of the voltage level. The discussion remains unresolved regarding the exact capacitance value needed.

Contextual Notes

Limitations include the lack of specific details about the pulse duration, load resistance, and the exact requirements for LED operation, which are necessary for precise calculations.

Daniel Floyd
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ok i need to know the value of the capacitor which i need.

i have a pulse voltage of 6mV which i want to stabilise to create a voltage which will power a small L.E.D. i currently have a bridge rectifier and i know i need a capacitor but what would the value of this capacitor be.
 
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6mV isn't going to power a LED... LED's are current driven ... ie. you need a constant current at a given voltage the common 5mm diameter LEDs require ~ 20mA

you had better expand a bit on where your 6mV is coming from
you are really going to need a few volts or so

Dave
 


Daniel Floyd said:
ok i need to know the value of the capacitor which i need.

i have a pulse voltage of 6mV which i want to stabilise to create a voltage which will power a small L.E.D. i currently have a bridge rectifier and i know i need a capacitor but what would the value of this capacitor be.

Maybe he means 6V pulse like in his old thread?

https://www.physicsforums.com/showthread.php?t=622069

.
 


The capacitance needed to stabilize a voltage pulse depends on several factors such as the frequency and duration of the pulse, the load resistance, and the desired level of stabilization. In order to determine the appropriate value of the capacitor, it is important to calculate the time constant of the circuit, which is the product of the capacitance and the load resistance. This time constant should be at least 5 times larger than the duration of the pulse in order to effectively stabilize the voltage.

For a pulse voltage of 6mV and an LED load, a small value capacitor in the range of microfarads (µF) or even picofarads (pF) may be sufficient. However, it is recommended to perform further calculations or simulations to determine the exact value of the capacitor needed for your specific circuit.

Additionally, the type and quality of the capacitor can also affect its performance in stabilizing the voltage pulse. It is important to choose a capacitor with low equivalent series resistance (ESR) and high capacitance stability to ensure proper stabilization.

In conclusion, the value of the capacitor needed to stabilize a voltage pulse depends on various factors and should be carefully calculated or simulated to ensure optimal performance in powering your LED.
 

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