Teensy and LEDs

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Now that my box is finished and I tested all lights I discovered that the LED lights on the pushbutton with green LED, pushbutton with red LED and the "engine start" pushbutton with red LED are very faint. Does anyone know what causes that?
Don't all pins on the Teensy 3.5 deliver 3.3 volts? If so they should in theory light up just as much as when I used my psu to test, which also delivers 3.3 volts.

In any case, I'm a bit tempted to just remove the resistors on those three LED lights. Because very low current seems to be flowing through them. (These values were measured with the psu, not the Teensy.):

Pushbutton with green LED: Rating: N/A
100ohm --> 0.45mA
120ohm --> 0.44mA
150ohm --> 0.43mA

Pushbutton with red LED: Rating: N/A
100ohm --> 0.65mA
120ohm --> N/A (forgot to measure)
150ohm --> 0.63mA

Engine start button with red LED: Rating: N/A
100ohm --> 0.65mA
120ohm --> 0.65mA
150ohm --> 0.43mA

Do they have some sort of built-in resistor you think? They are designed for 12V originally.
In contrast, here are the values for the red rocker switch, which is rated at max 10mA. As you can see this clearly needs a resistor. I now use 150ohm when connected to the Teensy, which gives lower mA than what you see below (those are measured with the psu).
100ohm --> 12.15mA
120ohm --> 10.27mA
150ohm --> 8.09mA
180ohm --> 7.06mA
 
If designed for 12V direct connect would expect they will have resistors to work at that voltage. Measure current against 12V if one handy not connected to Teensy.
 
Thanks, yes I suppose they have a resistor which is oversized for 3V.
I don't have a 12V psu, so I think I'll just remove the resistors in my box and measure directly on my Teensy, and hope they light up a little bit more.

It's not a big deal though. It's pretty dark where I use them. And I'm just using them as indicators, not to light up the room. :)
 
Please avoid removing the resistors and plugging the LEDs directly to the Teensy pins.
You risk damaging the Teensy.

You don't need a 12V PSU to measure the current:

Replace your resistor with a very small one (example: 10 Ohm, neat and easy)
Feed 3.3V from the PSU you linked before
Observe the brightness and measure the voltage across the 10 Ohm resistor
Divide the voltage by the 10 Ohm, and you'll get the current flowing through the LED with good approximation (because 10 Ohm are sure way lower than the integrated unknown resistor)
 
Please avoid removing the resistors and plugging the LEDs directly to the Teensy pins.
Ok, I won't do that.
Replace your resistor with a very small one (example: 10 Ohm, neat and easy)
Feed 3.3V from the PSU you linked before
Observe the brightness and measure the voltage across the 10 Ohm resistor
Divide the voltage by the 10 Ohm, and you'll get the current flowing through the LED with good approximation (because 10 Ohm are sure way lower than the integrated unknown resistor)
Ok, so same procedure as earlier then, only with much lower resistance.

Btw, I also noticed something in a review of a cable extension that I'm using to feed the USB-signals/power into the box: https://www.amazon.co.uk/gp/product/B06XZ2NFP1/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1
Two of the reviews says that it drops voltage. Could this also damage the Teensy, or is the worst that can happen reduced LED brightness, which I think I'm getting?
 
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