nOOds Flexible LEDs and Current Limiting Resistors

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sv98229
 
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nOOds Flexible LEDs and Current Limiting Resistors

Post by sv98229 »

Trying to get a better understanding for the nOOds flexible LED specifications.

What are the flexible nOOds LED's forward voltage drop and forward current values used by Phillip Burgess in the Adafruit nOOds Überguide to calculate a 50 ohm current limiting resistor for 3V power supply and a 220 ohm current limiting resistor for 5V power supply?

What confuses the issue:

The nOOds - Flexible LED Filament - 3V 300mm long - Lime Green Product ID: 5507 product page recommends current limiting with a resistor to let max 50mA through with a 3V power supply.

In Adafruit's New Products 8/31/2022 Featuring n00ds video using a 1K current limiting resistor for a 5V power supply was mentioned.

Doing some simple calculations with the Überguide values the forward voltage drop for the flexible nOOds would be -

* 0.5V based on a 3V power supply and a 50 ohm resistor
* 6V based on a 5V power supply and a 220 ohm resistor

Plus the Überguide's 3V/50 ohm and 5V/220 ohm recommendations imply the 1K resistor default mentioned in the new product video would be five times larger than needed and would mess with the nOOds performance.

I get uncomfortable blindly using values that aren't from a datasheet - to many items have gone up in smoke.

Having good values for the flexible nOOds LED's forward voltage drops and forward current values would be a big help.

Rather than being limited to trial and error we could actually calculate current limiting resistor values for our nOOds projects.

Which brings to mind another question - different color LEDs more often than not have different forward voltage drops and forward current values. Would the same concept apply to the different color nOOds?

Thanks. The help and advice is appreciated.

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adafruit_support_mike
 
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Re: nOOds Flexible LEDs and Current Limiting Resistors

Post by adafruit_support_mike »

sv98229 wrote: Tue Sep 06, 2022 1:23 pm different color LEDs more often than not have different forward voltage drops and forward current values. Would the same concept apply to the different color nOOds?
Yes. It applies directly.

The strips are made from several ultra-efficient LEDs operating in parallel. Together, the whole strip is basically equivalent to two regular 25mA LEDs.

The load resistor calculations for regular LEDs of various colors will give you suitable results for the nOOds strips. Just set the maximum current at 50mA instead of 25mA.

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sethcim
 
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Re: nOOds Flexible LEDs and Current Limiting Resistors

Post by sethcim »

I measured the Vf of the pink 300mm noods as 2.79V @ 50 mA. It would be helpful to have this documented for all colors.

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jetforme
 
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Re: nOOds Flexible LEDs and Current Limiting Resistors

Post by jetforme »

@adafruit_support_mike, are there no data sheets for the n00ds? I'd feel a lot better designing these into my project if I could see proper data sheets.

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adafruit_support_mike
 
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Re: nOOds Flexible LEDs and Current Limiting Resistors

Post by adafruit_support_mike »

jetforme wrote: Mon Sep 12, 2022 6:05 pm are there no data sheets for the n00ds?
Nope. We link any documents we have on the product page or on a Downloads page in the main tutorial.

The vendor for those doesn't provide any datasheets. And to get ahead of the next probable question, our supplier contracts forbid sharing source information with third parties.

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sv98229
 
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Re: nOOds Flexible LEDs and Current Limiting Resistors

Post by sv98229 »

A little more information on nOOds:

Links for:
How to measure the forward voltage for an LED:

https://www.onelectrontech.com/lab-meas ... d-voltage/
Lab: Measuring LED Forward Voltage

How the LED filaments are made:

https://www.youtube.com/watch?v=tykxeuyfX5Q
How long LED filaments are made

Online some of the filaments included a CRI rating in their specs.
This is a definition of CRI and why it may influence LED choices.

https://www.flexfireleds.com/color-rend ... at-is-cri/
What is Color Rendering Index (CRI) and Why Is It Important to LED Lighting?

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gadgetfreak
 
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Re: nOOds Flexible LEDs and Current Limiting Resistors

Post by gadgetfreak »

wanted to make my first LED project! a necklace.
so I wanted to buy the Yellow one https://www.adafruit.com/product/5503
how long would this battery last https://www.adafruit.com/product/1317 ?

which resistor would i put on ? https://www.adafruit.com/?q=resistor&sort=BestMatch

I wanted to try to use a magnet clasp as well. friend had made a necklace where they use neodymium magnet as the clasp and when it connected it powered on as it connected the loop. would appreciate any help.

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Saras161
 
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Re: nOOds Flexible LEDs and Current Limiting Resistors

Post by Saras161 »

sethcim wrote: Mon Sep 12, 2022 10:38 am I measured the Vf of the pink 300mm noods as 2.79V @ 50 mA. It would be helpful to have this documented for all colors.
Hi, do you mind sharing the power supply and resistor you used to power the pink nood you tested?

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squirrel_oak
 
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Re: nOOds Flexible LEDs and Current Limiting Resistors

Post by squirrel_oak »

Hi, I’m a little disappointed in the brightness of the noods when powered directly from a GPIO output pin.

Would it be recommended to use a MOSFET, or something, to transistor power from another source?

-squirrel_oak

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adafruit_support_mike
 
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Re: nOOds Flexible LEDs and Current Limiting Resistors

Post by adafruit_support_mike »

Yeah, you'll get more current with a mosfet or BJT.

Most 8-bit microcontrollers can deliver about 25mA from a GPIO pin, but 32-bit microcontrollers are usually limited to the 3mA to 5mA range. They're build for smarts, not power.

The 2n7000 is probably the most common small-signal n-mosfet, with the BSS138 a close second. Both can handle 50mA easily, and turn on when their gate voltage is about 2V higher than the source.

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