Didn´t light on.
Covering from light or exposing to it DIDN´T make difference.
A picture might help.
Explain directly polarized and inversy (?) polarized. so we are all on the same page.
You did not say if light exposure made any difference during the diode mode test.
5V @270 Ohm is about 18mA. some LED's take about 20mA to light up.
If it is/was IR, how do you propose to know if it light up?
How are you determining this?You will not be able to see the light from an IR emitter. You may be able to see it through a camera viewfinder but only dim. What you really want is a camera without any IR filter. The NOIR Raspberry Pi is one such camera.
The voltage required to light an IR emitter is in the order of 0.7 to 1.4V so you don't need a higher one.
It wont, if it is a detector there will be an IR filter built in to stop that happening.
What forward voltage do you get at room temperature with 1 -- 10mA or so forward current?
Silicon photodetectors (0.7V) will be a lot less than a IR LED (1.1V), IIRC.Photo emitters are not silicon, but a direct-bandgap semiconductor (normally). Of coursea photodiode doesn't have to be silicon, but many are.
Tried again, with 1V5. Nothing
It sees perfectly all the other IE LEDs I have,
Directly polarized is, as in every electronic component: anode connected to positive of the power supply and cathode connected to the negative. Inverse polarized is the opposite. Perhaps I didn´t choose the correct expression because I´m not english.A diode, either IR or Visible Light must not let pass any current if inverse polarized, and must have a 1.3 - 2-5 voltage drop if directly polarized.
I don´t understand what do you mean