How Much Voltage and Current Do I Need for 8 LEDs in Series and Parallel?

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Discussion Overview

The discussion revolves around the voltage and current requirements for powering 8 LEDs configured in both series and parallel arrangements. Participants explore the implications of these configurations on power supply specifications, including voltage, current, and the use of resistors for current stabilization.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant suggests that for 8 LEDs in series, a total of 24V and 30mA is needed from the power supply.
  • Another participant confirms the need for at least 24 volts at 30mA for the series circuit, calculating a power requirement of 720 milliwatts.
  • In parallel, one participant proposes that 3V is sufficient, but the total current would be 240mA, as each LED would still require 30mA.
  • Another participant emphasizes the importance of using a resistor in series to ensure safety and stability in both configurations.
  • One participant raises concerns about LED current sensitivity to voltage and temperature, suggesting that each parallel path should include a resistor to stabilize current.
  • A specific configuration is proposed involving 4 LEDs in series or 3 LEDs with a resistor to maintain current stability, noting that different resistor values affect efficiency.

Areas of Agreement / Disagreement

Participants generally agree on the voltage and current requirements for the series configuration but have differing views on the implications and configurations for the parallel setup. The discussion includes multiple competing views on the best practices for using resistors and managing current.

Contextual Notes

There are unresolved assumptions regarding the optimal voltage supply and the specific resistor values needed for current stabilization in various configurations. The discussion does not reach a consensus on the best approach to take.

Who May Find This Useful

This discussion may be useful for individuals interested in electronics, particularly those working with LED circuits and seeking to understand power supply requirements and current management techniques.

ChrisToffer
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If i have a LED which drops 3V, and 30mA through each LED and i need 8 LED in series.. does it mean that i need a total of 24V and 30mA from power supply or less?
And if i use the same circuit in parallel, does it mean i will use 3V but much more current like 0.24A?? or least current?
 
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For your series circuit, I believe you would need at least 24 volts at 30 ma.

That's 720 mwatts from your source.

For parallel, 3 volts will work with 240 ma coming from source, yet each branch will get it's 30ma.

That's also 720 mwatts from your source.
 
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ChrisToffer said:
If i have a LED which drops 3V, and 30mA through each LED and i need 8 LED in series.. does it mean that i need a total of 24V and 30mA from power supply or less?
Why less? You'll need 24V and 30mA. It is safer to use a voltage a bit above 24V together with a suitable resistor in series.

And if i use the same circuit in parallel, does it mean i will use 3V but much more current like 0.24A?? or least current?
8*30mA of course. The same advice: use a resistor in series.
 
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LED current is highly sensitive to applied voltage and temperature.
Each parallel path will require a resistor to stabilise the current in that path.

Consider a 12.00 volt DC supply for 8 LEDs.
4 LEDs in series would give no control of current at varying temperatures.

3 LEDs and a 100 ohm resistor in each series chain would stabilise the current at 30 mA. One of the three chains will need an extra 100 ohm resistor or a hidden LED to make 8 visible LEDs total.

2 LEDs with 200 ohms in series will be less efficient than 3 LEDs with 100 ohms.
 
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