Linked Questions

25 votes
2 answers
172k views

Why we use 330 ohm resistor to connect a LED? [duplicate]

Possible Duplicate: Correct formula for LED current-limiting resistor? Why we use 330 ohm resistor to connect a LED ? I mean: the R is by practice 330 ohm. Why this value? How do I calculate ...
xsari3x's user avatar
  • 1,608
0 votes
1 answer
405 views

Connecting nine LEDs in series.. why the results? [duplicate]

I asked this before but I'm having problems still. I need to connect nine LEDs in parallel with a 9 volt battery. The wire leading away from the 9V separates into three and on each three are three ...
Ken Garber's user avatar
1 vote
1 answer
578 views

Connecting an always on LED to a raspberry pi [duplicate]

I'm new to electronics, so I thought I'd start simple and just connect an LED to the GPIO on the raspberry pi, to pin 1 (3.3v) and the ground pin. But I'm having trouble calculating the resistor I ...
Jonathan.'s user avatar
  • 457
3 votes
1 answer
325 views

Is a resistor needed for LEDs in this beatbox project? [duplicate]

I'm making a LED beatbox (seen on Kipkay.com). I'm using 8 LEDs (5 millimeters, I don't know if this helps) and my power source is 12 VDC 800 mA. Do I need to add a resistor? If yes, which one should ...
Gabriel's user avatar
  • 31
1 vote
2 answers
359 views

What resistors do I need for my LED? [duplicate]

I don't really know the whole technology thing so this is why I'm asking. I bought "20PCS 5mm IR infrared LED 940nm Lamp High Power" for head tracking and I don't know what resistors will be good for ...
Lidor Buba's user avatar
2 votes
2 answers
123 views

What is the resistor for 3 watt green led in series [duplicate]

3 green leds (button leds) are connected in series. Using 12 volts car battery and a simple current limiting using resistor, avoiding constant current. Good heatsink is used. No standard spec is ...
user avatar
-2 votes
1 answer
1k views

LED's too dim. Wrong resistor? [duplicate]

I'm a halloween tinkerer, and I have these UV/Blacklight flashlights that I use in my decor, but they eat batteries like crazy. They start going dim within an hour or so. So, since I already have ...
Troy Pruyt's user avatar
-3 votes
1 answer
103 views

I want to wire a single led off a motorcycle battery [duplicate]

I want to use my motorcycle battery to power a single led that has a maximum voltage of 3.6 volts. what resistance do i need to drop the voltage from 12 volt to 3?
Elijah Rydzewski's user avatar
0 votes
1 answer
86 views

Lighting LEDs from high current source [duplicate]

I have an circuit with six high torque servos connected parallel to power brick that provides 5V @5Amps. Everything is running fine. But I wanted to add few LEDs to circuit but I dont know how do I do ...
Amrit Sohal's user avatar
-2 votes
2 answers
99 views

Help with simple Circuit [duplicate]

I am hoping that someone can help me to calculate voltage and current to the LED socket. I see that there are 3 batteries in series, plus a resistor (?). Thank you very much.
lagold's user avatar
  • 3
0 votes
1 answer
65 views

How much voltage I need to light up this led [duplicate]

I have a RL80-UR543 LED 8MM. How much voltage I need if I use a resistor of 100Ohm?
No Namer's user avatar
158 votes
4 answers
79k views

How can I efficiently drive an LED?

I understand that I can not connect an LED directly to a battery because it will draw too much current. Thus, there must be something else in the circuit to limit the current. What options are there? ...
Phil Frost's user avatar
  • 57.6k
13 votes
4 answers
63k views

How do I calculate the resistor value for a simple LED circuit?

I have a simple circuit: The max rating (current) of the LED is 30mA. How can I work out what the resistance of the resistor needs to be? By using ohm's law I found it to be \$3V/0.03A = 100 \Omega\$...
Jonathan.'s user avatar
  • 457
11 votes
4 answers
15k views

Voltage drops and current for LED?

I created the following circuit on a breadboard and used the Arduino Uno 3.3V supply for the power supply: ...
rrazd's user avatar
  • 1,677
16 votes
3 answers
3k views

Why use LNAs in a noise generator?

In this Maxim appnote the avalanche noise of a zener diode is amplified by two cascaded LNAs (Low-Noise Amplifiers): You can guess what my question is: why use low-noise amplifiers if you want ...
Federico Russo's user avatar

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