Linked Questions
10 questions linked to/from Is a current-limiting resistor required for LEDs if the forward voltage and supply voltage are equal?
2
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Do I need a resistor or no? [duplicate]
I'm working with 6 LEDs in series, which are rated at:
3V Typical / 3.2V Maximum
20mA.
My power supply is:
19V
3A Maximum
According to my calculations:
I'd need a 50 ohm resistor at 3V
I'd be in ...
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42
votes
12
answers
27k
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Doesn't using resistors serial to LEDs all the time waste a lot of energy?
I was wondering for a long time why in schemes which use LEDs for lighting it's very common to put a resistor to go with the LED, and finally it seems like the answer in this question explains why. (...
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5
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5
answers
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Which is better: using a resistor with an LED, or "precisely" matching the Vs to the given LED's Vf rating?
Here's an example:
Suppose I have an LED with a Vf rating of 3.6 V ....Here are two things I could try:
1) use a single 3.6 V 18650 Li-Ion cell with no resistor [\$V_s = V_f\$]
or
2) use three 1.5 ...
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8
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1
answer
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9-volt battery connected to transistor controlling LEDs with Arduino
I am trying to add a custom LED lighting setup to my desktop gaming computer. In this setup I want small sets of LEDs to be able to be turned on separate of other sets. This is so that I can turn on ...
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1
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4
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7k
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Infra Red LEDs - Voltage Advice
I've built an array of Infra Red LEDs on a 4x4 grid. I want to get the most power out of these LEDs as I can, but I'm scared I might burn them out.
Right now, I'm using 2AA batteries (1.5V each), ...
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0
votes
1
answer
1k
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Calculating LED current using ohms law
I've got a 4 digit green 7 segment display (technically 5, it's from a microwave and the "5th" digit is the function lights on the top and bottom). I don't have a datasheet for it. It's common cathode,...
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0
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2
answers
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Different LEDs in parallel
Are there any special considerations I should pay attention to, when I wire multiple LEDs in Parallel?
I am doing a project with a 100 LEDs in parallel. Each LED could be a different color, and each ...
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1
vote
1
answer
166
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Do I need trivial resistor or not if V/I = zero or almost zero
As the title says, do I need trivial resistor or not if V/I = zero or almost zero?
For instance:
Assume I'm using 3V buzzer and 2V LED in series with an Arduino 5V pin.
$$R = \frac{(3 + 2 - 5)V}{...
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-2
votes
1
answer
107
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Do I have to use current limiting resistor for LED in this configuration?
LM741 datasheet says that it can output a maximum of 20-25 mA. So in this case, is that R5 a must, or will it be safe not using it?
Assuming LEDs can withstand 25mA.
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2
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1
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Why do I have to increase the current by 2V when I am using a transistor?
I have a 3V 3W LED, which I would like to control with an ESP32.
For controlling the LED, I have chosen a TP122 transistor.
Here is my 'schematic':
The Arduino is an ESP in real life, and the 3 V ...
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