Nucleo Leds are too bright

[gregstm]

Is there a prize for the most trivial post?

Opened up a new Nucleo-L476RG board (finally worked my way through the 10+ boards I bought a number of years ago) - it comes in a cardboard box now, nice.

The Leds (LD1, LD3) were so bright, I couldn't probe anywhere around the micro or connectors without squinting. So I replaced the resistors for these Leds (1K, 100?) with 22K, things are much more mellow now.

Most people are using these boards indoors, the Leds only have to be bright enough for people to notice - not beaming out like the Eye of Sauron. 

Anyway, something for you to think about. Meanwhile, there's a few annoying clouds outside I need to shout at....

[Ozone]

On a related note ...

I recently revived a FRDM-K64F board, which I had purchased back then when Freescale was still a thing.

Trying an example for the onboard RGB-LED nothing worked - or so it seems.
The code was fine, the GPIOs are set correctly and the voltages on the LED looked ok, but no light.
Not sure if it ever worked, though. Or if it bothers me much.

The funny thing is, the LED datasheet specifies a VF of 3.3 ... 4.0V for green and blue (2.4...3.0V for red). Which seems highly optimistic for a 3.3V MCU ...

[gregstm]

The revision is MB1136-L476RG-C05, the number K254000714 is also on the sticker.

It's good that Leds are getting more efficient, but it can make getting the brightness right tricky. The LD3 Led with a 22K resistor is using about  0.15 milliamps - and yet it is still plenty bright enough for me, that's pretty electron thrifty!

I must emphasise, I do appreciate these little Nucleo boards, they make testing out ideas pretty easy.

[Ozone]

> I must emphasise, I do appreciate these little Nucleo boards, they make testing out ideas pretty easy.

Me too ...
And these boards are quite useful for real-world projects, in contrast to some stuffed discovery board were two thirds or more of GPIOs are captured by special onboard features.

Although I would like to have even smaller Nucleo's, e.g. with MCUs in a TSSOP20 package.

[David Littell]

Nucleo's are indeed very useful for proof-of-concept development but please note that they are NOT intended to be deployed.  I believe ST has noted this in the past (in some other thread) - full design due diligence is required.

[Andrew Neil]

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@David Littell wrote:

 I believe ST has noted this in the past

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It's in the Terms Of Use:

https://www.st.com/resource/en/evaluation_board_terms_of_use/evaluationproductlicenseagreement.pdf

eg, via: https://www.st.com/en/evaluation-tools/stm32-nucleo-boards/documentation.html

[unsigned_char_array]

Technically it's not the brightness it's the illuminance.
These LEDs are so small that even with low brightness/luminous flux in Lumen they have high illuminance in Lux.

Adding a diffuser/frosted cover on top would help. The diffuser spreads the light over a larger area. I often add some paper on top of bright LEDs. They act as a diffuser and spread the light over a larger area and also block some of the light. And with RGB LEDs it also helps mix the colors. A PCB mounted light pipe can also help.

It's certainly not trivial. It's not good for your eyes.

[Ozone]

I speak about my private / hobby projects here, not commercial ones.
Just to clarify that.

I'm well aware they are not made for integration in commercial products, and ST dismisses any claims regarding such a use. As is usual in this industry.