On November 9, 2022 at 12:56, Fred Harding said...
Beg to differ on the 3 conductor emitter. The flash was something you bought as a feature or not; Xantech 283 was flash, 282 was no flash. Same 3.5 mm male mono plug for either.
Yes.
And Fred should (nd does) know this better than we do because if he sent the wrong product, his customer had problems!
Blanket statement: I've NEVER seen an emitter with a three-conductor plug.
Another detail about the blink IRs is that they had two LEDs, in series, in each one, with a series resistor; one LED was an IR emitter, the other was a visible light emitter. All LEDs have a voltage drop across them, so if a blink IR was used with an IR system using 5 volts, there might not be enough voltage to light up the LEDs.
Fred just reminded me that the brand I was talking about, that operated at 5 volts, was Niles.
On November 10, 2022 at 11:31, tomciara said...
Electrically speaking, there is no need for a third conductor as the emitter for the equipment and the visible LED can simply be paralleled.
Well, maybe.
Two LEDs can be paralleled if they turn on at EXACTLY the same voltage. If one LED turns on at, say, 2.2 volts and another in parallel with that one turns on at 2.3 volts, then the 2.3 volt one will never turn on because the 2.2 volt one will pull the voltage across the diodes down to 2.2 volts.
If all the LEDs turn on at exactly the same voltage, then two in parallel can work. LEDs from the same manufacturing batch have the greatest likelihood of having identical turn-on voltages. Since we generally see LEDs of the same batch, their turn-on voltages rarely differ. But they can.
The reason for a resistor in series with an LED is to make sure that no single LED drags the applied voltage down below where other LEDs would turn on.
