On October 11, 2017 at 00:34, tomciara said...
I see your technical reasoning behind why two emitters in parallel will not work. I also see the original poster can't get them to work. Only trouble is, I have done it many many times without an issue.
That's not trouble. As I mentioned, LEDs are made in batches and the units in the batches are substantially identical to one another. That means that in the usual world of manufactured double LEDs, or taking two LEDs from a package, they will most likely work. I said we should use sharing resistors to ENSURE that any possible different turn-on voltages won't cause failures. One unmatched pair will drive you nuts until you remember this thread, so I recommend standardizing on curing the potential problem first.
In fact, I order what amounts to being a mini plug splitter, that would normally be used for two sets of headphones off of an audio device, and I use it to drive two emitters off of one port.
Are these emitters probably from the same batch? Do they have resistors built into them? (To test this, vary the voltage applied to them through a resistor. If, after the LED starts to conduct, the voltage across the LED [or LED plus resistor] increases as the applied voltage increases, then there's a resistor built in in series with the diode.)
See, it doesn't matter if these have all worked. What will matter much more to someone is if a pair doesn't work.
I did it today when the client wanted me to add an emitter to control his old Denon compact disc changer with his URC remote. It worked.
Perhaps there is something forgiving about URC base stations, or URC emitters. Whatever the case, I have done it multiple times over the years and have never had it fail.
If the URC emitters have resistors in series with the LED, that would take care of the potential problem.
