Hello!
Currently I'm working on a project in which an ESP8266 (NodeMCU v0.9) will control a TV using an IR LED (a Universal IR Remote project).
The LED I bought from the online store has no name, so I can't provide the datasheet. I've read online that the typical IR LED maximum current is about 100mA and that some people suggested just below 100mA should be enough for hobbyist projects.
So I designed the following circuit [see image 1]. Which gives just about the right output current from ESP (~11 mA) and current on IR LED (~80 mA) according to simulation below [see image 2].
But when I tested it, the IR LED just won't light up enough to be able to control my TV even from a distance of 1 meter (I checked using my smartphone camera and the light is very faint).
So I decided to remove the 20 Ohm resistor so that the circuit looks like this [see image 3]. And now the remote works perfectly fine up to 3 meters. But according to simulation, the circuit would produce a current of about ~500 mA on the IR LED [see image 4].
Curious, I decided to measure the IR LED current with a DMM using the DC Ampere setting. It only shows a current of about 7.5 mA.
I have a few questions regarding this (sorry if some of them are stupid):
1. Is 80 mA not enough for an IR remote from 1 meter range? What's the adequate amperage?
2. Is it okay to remove the 20 Ohm resistance? As far as I know LEDs have very little resistance and I'm surprised that it works and nothing burns.
3. Why does my DMM measure a current of only 7.5 mA? I know that this has something to do with duty cycles and averaging of currents. But then how can I verify the circuits I designed and simulated?
Thank you very much. This is my first post here