Linked Questions

15
votes
6answers
3k views

Will using a resistor in series with a LED to control its voltage increase the total energy expenditure? [duplicate]

This might sound like a stupid question, but I want a confirmation. I watched a video on Youtube about using LEDs. Those LEDs required a voltage around 2 volts at 20 mA. In order to power one LED ...
3
votes
3answers
4k views

Calculate expected voltage around a resistor [duplicate]

It's been a few years since I first studied the Ohm's law at school. Now I'm really getting into electronics, and I must admit a part of it still puzzles me. I know this is kind of a strange question,...
5
votes
5answers
744 views

Dynamically dimming individual LEDs in a lighting system [duplicate]

I'm planning to build an aquarium lightning system with individually controllable LED's, I don't have much experience with electronics except from the irregular tinkering, but I'm a programmer and I ...
0
votes
1answer
2k views

How can I decrease a DC voltage without a resistor [duplicate]

I would like to light up a 2 W LED with a 3.7 V power source in the most efficient way possible. The Vf of the LED is 2.4 V. Is there any way I can reduce the voltage to 2.4 V from 3.7 V without using ...
-2
votes
1answer
2k views

How to power led from arduino [duplicate]

I am new to electronics and ohms law is confusing. When I power the led with analogWrite and give it only 3 volts do I have to still use a resistor? When I power the led with 5 volts does it matter ...
1
vote
2answers
268 views

How do I drive 12 strings of 12 leds each? [duplicate]

I would like to drive 144 leds with a battery power supply. I want to drive all the leds all the time. 12 leds in series on each string. The Led specs are: ...
-1
votes
2answers
84 views

Driving various LEDs with one voltage supply [duplicate]

...
-1
votes
1answer
90 views

What resistors to use for 60, 8000mcd LEDs, with 4 * 1.5v battery source? [duplicate]

I currently have 60 LEDs in a parallel circuit. I am using 4 1.5v batteries as the source. The LEDs have a forward voltage of 3v-3.4v (8000mcd, wavelength 460nm). My questions are: Can I just use ...
129
votes
6answers
87k views

Why exactly can't a single resistor be used for many parallel LEDs?

Why can't you use a single resistor for a number of LEDs in parallel instead of one each?
40
votes
7answers
23k views

Why can't I light a LED with a 1.5 V battery?

The LED I am using requires a higher voltage to light than I have supplied, and as a result, it doesn't light at all. I would expect at least a dim light, but light is not generated. Why this ...
49
votes
6answers
22k views

Does pulsing an LED at higher current yield greater apparent brightness?

This question implies two assumptions: The frequency of a switched LED driver is high enough that average power, not instantaneous power, should be used to determine maximum drive current. The ...
38
votes
2answers
20k views

Correct formula for LED current-limiting resistor?

I'm trying to work out what value resistor to use in a LED circuit. The equation I'd use to do this is: $$ R = \frac{V_{cc} - V_f}{I_f} $$ Seems logical, and makes complete sense. The answers to the ...
18
votes
5answers
39k views

Is it OK to put LEDs in parallel? [duplicate]

I wonder if it's a good idea to put LEDs in parallel, as below: I've heard that it might not be because the voltage threshold won't be exactly the same for each LED, so they'll shine all with very ...
7
votes
8answers
11k views

When does the placement of a resistor matter?

I've been a programmer for years but am very new to electronic engineering. So far I see people saying it doesn't matter where a resistor goes in your LED circuit as long as it is present, but it ...
4
votes
11answers
2k views

Uniformly illuminate an array of LEDs: how to get the most homogeneous output?

Please note: this question refers to the electrical engineering part of the design, optical configuration is not request (advices are however welcome) I'm trying to design a LEDs lamp with an ...

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