I have a strange question. Hopefully I can get some insights
Previously i had 4 LEDs connected to my esp8266 nodemcu board, each LED connected to 1 pin as output and have been working fine.
One day one of the LEDs got much darkened. And then i did quite a few tests to troubleshoot like
connect that malfunction LED to other pin that confirmed working
connect another working LED to that pin
connect that malfunction LED in parallel with another working LED.
In all the scenario, the malfunction LED is still the same while those working LED works in every cases.
However, i connect the malfunction LED to the 3.3v pin directly and it is working.
I have no clue about what's going on.
My project is actually replacing the device powered by 3 LR41 batteries with arduino output.
I have limited knowledge about those electrical matters. Can you correct my understanding:
Actually the LED was previously powered by 3 LR41 batteries and I thought that should be 4.5v and even directly connect to the Pin (~3v). I am still providing less voltage then it was designed?
How much ohms I should use? I tried using a potentiometer from 0 to 500 ohms, and found that even using 0ohms resulted in darker then I just put 3 LR41 batteries which was the designed power supply.
One thing I cannot understand is that when I connect the damaged LED to 3.3v pin of the board or connect to the original batteries (3 X LR41) it can light as bright as it was. Does it mean the LED is "burning out" but not completely dead?
I also think it didn't burn as it was working when i connected it back to batteries.
My decision not to use resistor is only based on the fact that the device was originally powered by 3 x 1.5v batteries and the pin is just ~3v which is even lowered. I am not sure if that implication is correct or there are other factorsto consider than just simply adding up the voltage
NOTE: Maybe the device itself has resistor inside that i don't know about and probably that's why it used 3 batteries before. I just mean i didn't put additional resistors between the pin and the device's input
Can you please post a copy of your circuit, a picture of a hand drawn circuit in jpg, png?
Hand drawn and photographed is perfectly acceptable.
Please include ALL hardware, power supplies, component names and pin labels.
Oh I see! Didn't know that the batteries have internal resistance.
Unfortunately, I don't have a data sheet because I am trying to convert my existing device which was powered by batteries.
But my observation is that in my first try, with my potentiometer even using the lowest value, it was still a bit darker than with batteries. Therefore, even with 220ohms, the LED wasn't as bright as with batteries. I am wondered how I can use resistor while have the same brightness as my batteries?
That is the problem.
Blue LEDs have very high forward voltages sometimes as high as 4.V To drive them with an 3.3V ESP output you will need a transistor driver for each LED and a 5V supply OR if you use RED LEDs, all you will need is a resistor.
I have a DMM, I measure the following and got some interesting observation, but not sure if that's a correct direction for the problem:
Put the positive of DMM to the pin and negative to the GND and confirm that the pin can output ~3v while the demaged LED got very dark. But other LEDs with that pin are fine.
Put the positive of DMM to the 3.3v pin and negative to the GND and got the same ~3v output. But interestingly, my demaged LED can be as bright as before.
I changed to resistance mode and measure just the demanged LED, it did have reading, I remember it is almost 200 ohms while with other healthy LED, I didn't get the same reading.
Here is my circuit, actually it is too simple (as that is my first project )
I see, that means it is not resistor that I need. It is not enough voltage to drive that I should use transistor with higher voltage?
But I remember the LED was functional for a few days.
NOTE: Actually I am trying to use arduino to control my Ironman , the problematic led is on the left leg while the right leg is okay so far (I assume they should be in the same spec)
NOTE2: I remember right before the LED got problematic, it did blink sometimes. At first, I thought that was due to some contact issue with the wire and then I rewire it. but then it happened.
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