Learn How to Calculate 12V DC LED Forward Current for SMD Chip 3528

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Discussion Overview

The discussion centers on calculating the forward current for SMD chip LEDs (specifically the 3528 model) in a 12V DC circuit configuration. Participants explore the arrangement of LEDs in series and parallel, as well as the implications for current and voltage distribution across the components.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant states that the standard forward current for the 3528 LED is 20 mA and seeks to understand how to calculate the forward current in their specific setup of 48 LEDs.
  • Another participant calculates that with 16 parallel LED strings drawing a total of 260 mA, each string would draw approximately 16.25 mA.
  • There is a clarification about the configuration of the LEDs, noting that they are arranged with 16 in parallel and 3 in series, with each LED requiring between 3.5 to 4 volts.
  • One participant suggests that there is likely a resistor in series with each string of 3 LEDs, estimating it to be around 100 ohms.
  • Another participant discusses the design approach, proposing to allocate 25% of the voltage for a series resistor and calculating the necessary resistor value based on the voltage drop across the LEDs.

Areas of Agreement / Disagreement

Participants express various methods for calculating forward current and resistor values, but there is no consensus on a single approach or formula. The discussion remains unresolved regarding the most straightforward calculation method.

Contextual Notes

Participants mention different assumptions about voltage drops and resistor values, which may affect the calculations. The discussion does not clarify the exact specifications of the power supply or the tolerances of the components used.

Who May Find This Useful

This discussion may be useful for electronics enthusiasts, hobbyists working with LED configurations, and individuals seeking to understand current calculations in LED circuits.

digitaltech
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We are using smd chip led 3528 which prescribe 20 miliamp standard forward current. I want to know basic calculation like those bulb. How do i find forward current?

12 volt dc light, 48 pc smd chip, 16 parallel connection 3 series (as each chip volt is 3.5 to 4)
Now we found that 3.14 watt is consuming this bulb means 0.26 amp consumption (12 volt). How we can found the each smd forward amp?
 
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You have 16 parallel LED strings drawing a total of 260 mA, so each one is drawing (260 mA / 16) or 16.25 mA.

Is that what you were asking?
 
The bulb is 12 volt running dc but as each smd using 3.5 to 4 volt that is why first 16 in parallel and and those three (16 pc parallel each parallel) three in series. If 12 volt condition total 48 pc smd consumed 260 mili each how much forward current?
 
16.25 mA.

The LEDs in series carry the same current.

Note that there is probably a resistor in series with each string of 3 LEDs. It might be about 100 ohms in this case.

Are you having a problem with this LED display?
 
How do we calculate them always? Like we can get the reading amp how much consumed say 0.26 amp 12 volt. Now divide to three series each series 4 volt and each series 16 pc parallel chip. Got any easy calculation?
 
digitaltech said:
How do we calculate them always? Like we can get the reading amp how much consumed say 0.26 amp 12 volt. Now divide to three series each series 4 volt and each series 16 pc parallel chip. Got any easy calculation?

Do you mean "how would we design this, using these LED's ?"I like to allow 25% of the voltage for a series resistor, so if I had 12 volts, I would work out how many 3.5 volt LEDs could use 9 volts.

It would be between 2 and 3 and this design uses 3.

OK, so using 3 LEDs which each use 3.5 volts, that would be 10.5 volts.

This leaves 1.5 volts for the resistor and the current is 20 mA. So the resistor has to be 1.5 volts / 0.02 amps or 75 ohms. To be safe, you would choose the next highest value which is 82 ohms.

So, you have an 82 ohm resistor in series with 3 LEDs, each dropping 3.5 volts. The series string would draw 20 mA approximately. You could put any number of these across a 12 volt supply as long as the supply could deliver the current.
 

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