Tuesday, November 25, 2014

Moto E and Moto G : 2 White LEDs

After my articles about the "Two LEDs" discovered on MotoE (and suspected on MotoG) i received a lot of questions about them : 
Moto G Falcon notification LED charging triggerMoto E Condor notification LED charging trigger

  • Are there really Two LEDs there??
  • Are they really White and not RGB "mis-configured"?

So i made non-destructive tests using a microscope on Moto E:
For some reason, MotoE LED hole is transparent and we can see through it (that's not the case for MotoG)

2 LEDs

The proof that MotoE has 2 LEDs

Here is a picture taken at x100 of the notification LED ON (triggered through /sys/class/leds/white since the brighter one was too bright to allow me to take a pic of it lighten up with my set up)

Moto E Condor notification LEDs x100 microscopy

Each "yellow" rectangle is a LED chip (you can see the two wires on the left one)
This is proof there is two LEDs, i was able to light them both using the following : 

echo 255 >/sys/class/leds/charging/brightness #to light the left and brighter one
echo 255 >/sys/class/leds/white/brightness #to light the one on the right

White LEDs

The proof that Moto E has white only LEDs
Moto E Condor notification white LED microscopy (Blue and phosphor coating)

On the above picture, you can see a closer view of the LED: its inner components and something interesting :

  • there are 2 wires: this should correspond to +/- (proof of Single color LED)
LED basic Scheme from wikipedia[source : Wikipedia]

  • The light emitted is white (that could be RGB set to 255:255:255) BUT, there is a Blue shift (the blue luminescence you can see around the center of the LED) which  corresponds to a Blue LED with a phosphor substract coated on it giving the White light.
BLUE Phosphor coated LED spectrum from wikipedia[source : Wikipedia]

We now know that Moto E has 2 LEDs and that they are White only

I cannot prove it for motoG until complete teardown (the LED hole does not allow to see through it and observe the LEDs) but there are good chances that it also has 2 white LEDs regarding the behavior in previous tests.

Make sure you read these articles to understand how this started :