Questions tagged [led]

An LED is a light-emitting diode. Lighting an LED is considered the "Hello world" of a circuit design, and it can be as simple as putting a series resistor or can get more complicated, involving PWM and multiplexing.

Filter by
Sorted by
Tagged with
0
votes
2answers
25 views

How much does voltage affect the light frequency output of an LED?

I have a large array of LEDs that I need to be true to their specsheet light frequency emission (ex 635 nm). The LED's require Vtyp @ 20 mA ranging from 2.2 V to 1.2 V. Some are within 0.1 V of each ...
0
votes
1answer
62 views

Resistor causing problems when in series with LED

I am wanting to dim the light on my computers power light, its just a 5mm LED what i am guessing gets 5v from the motherboard to power it The problem I am having is that when adding a 100R resistor ...
0
votes
5answers
75 views

LED lamp - connecting LEDs in parallel

I have a question about LED lamp: Quantum Board It has 16 strings of LEDs connected in parallel. Each string consist of 18 LEDs connected in series. It's supplied with constant current source (with ...
-1
votes
0answers
68 views

Need simple, passive circuit to intermittently flash an LED

I am trying to make a simple flashing LED toy to get a 5-year-old boy interested in electronics. The LED should blink for the shortest time possible Remain off for five or ten seconds between flashes ...
1
vote
2answers
81 views

Small electronic project kit

I ordered this electronics project kit which consists of a small PCB. You have to solder the components onto the board. The components are: Two 510 ohm resistors (green, brown, brown) Two 33k ohm ...
5
votes
2answers
2k views

Spectrum of LEDs [closed]

How monochromatic is the light from LEDs? I want a set of light sources which will emit light of different wavelengths, as narrow a spectrum as practical. How wide are the spectrums of typical LEDs?
-4
votes
1answer
67 views

I have a LED panel with 42 leds and I don't have the data sheet. How can I find the input voltage and current? [closed]

I have a LED panel with 42 LEDs and I don't have the datasheet. How can I find the input voltage and current of the panel?
3
votes
2answers
107 views

Push button for different actions in every press?

I'm trying to learn some electronics and I have something in mind that I don't know if it is possible to achieve. I've worked before with micro-controllers (Arduino, etc) and I know I would be able ...
0
votes
2answers
102 views

Can I add two LEDs to this circuit?

I am working on a diorama. I found this circuit online and it's what I want. (I'm NOT making a railroad diorama.) I want to add two more LEDs to this circuit to have 4 flashing LEDs. Like this: ...
0
votes
1answer
29 views

Individual Digital Control Of LED Array

I am working to create a portable educational element display (about 2 meters wide) along the lines of this one at Griffith Observatory: http://www.griffithobservatory.org/exhibits/...
0
votes
1answer
38 views

Minimum g9 led current

I am trying to find out the minimum current of a LAP 220V 2.78W g9 led. Is there an IV curve available for this product? None of the data sheets I have found show any minimum current requirements or ...
0
votes
0answers
33 views

LED room lighting 15m

I want to decorate the ceiling of my room with LED strips. This would be a total of 15 meters (3 * 5 meters) of LED strips, The led stripes have 60 leds per meter IP30. my plan was that I could ...
0
votes
2answers
78 views

Why does LED dim when adding second LED in parallel with a single resistor

If I have a led hooked up to a 12v DC supply with a single resistor it runs nicely as you would expect. If I add a second LED in parallel the brightness drops, slightly, the brightness on both is (to ...
0
votes
3answers
62 views

What’s the difference between led current draw with and without PWM?

I have a LED that’s rated for 3W (aprox 3V and 1A max current) Do I get the same result in terms of current draw and led’s durability if I supply the led with a 1A Led Driver (at full current supply, ...
1
vote
1answer
60 views

Review of my LED spinner Schematic

After a few months of questions and modifications to my design. I have what I believe to be a LED Spinner that can change the speed of the spinning LED. Before I send this design off to get printed on ...
0
votes
2answers
113 views

LEDs in series without resistor

Say I have an ideal situation (good quality functioning power source and components) - 12V source and 3V (each) LEDs. Can I wire these 5 LEDs in series to the 12V source without a series resistor and ...
4
votes
1answer
82 views

Choosing LED brightness

I am planning to build an electronic fencing scoring apparatus for training purposes in our club (so no FIE certification required, it's a pure hobby project). For hit indication, I want to use a ...
3
votes
2answers
166 views

How can I fix EMC problem over my PCB?

Here is my PCB drawing that couldn't fix EMC problem. There are peaks at 120-130 MHz at radiated measurement. Are there anyone who have any opinion to fix this? Note: My circuit behave as led driver ...
0
votes
1answer
62 views

What temperature should I expect by lighting 3W-LEDs?

I have a PCB with 10 LEDs (reference : SPHWH2L3D30ED4TPK3) which will each dissipate 3 W (forward voltage of 3 V and 1 A passing through). The PCB is a circle with a diameter of 20 cm and LEDs are ...
0
votes
1answer
39 views

High Power LED Circuit Design & Constant Current Source Question/Feedback

I'm trying to design a dimmable LED circuit board. It's controlled by Arduino with its PWM signals. I'm new to electronics so I have some question regarding my design and knowledge on it. I've ...
0
votes
1answer
36 views

Issues encountered when adding DC adapter to light powered by battery

I have an LED light bar powered by 6 AA batteries connected in series. There is also an RF control unit to turn the light on/off. The light eats through the batteries rather quickly thus I decided to ...
0
votes
3answers
90 views

Fail safe led circuit

My question is about how to turn on a led before the GPIO pin has been initiated. When the IC has just been powered on and has not yet been initiated the GPIO pins remains in state HI-Z. In Circuit-1 ...
11
votes
1answer
611 views

Minimum recommended LED drive current

I've stumbled upon a LED's datasheet that includes a strange recommendation. They want me to drive the LED at >5mA for reasons of "long term performance." I've never seen a similar thing anywhere else,...
0
votes
1answer
57 views

MOSFET for switching single LED

I try to design a cost-effective but still "reasonably engineered" way of driving a single white LED with a micocontroller with the following "specs": For the single white LED no extra boost ...
0
votes
0answers
44 views

How can I repair this LED bulb which turns on and off irregularly while the switch is in the on position? [closed]

This happens both for some LED bulbs and for some fluorescent lights after they have worked for a few months: the switch is on, but the light goes on and off irregularly. It seems to be due to some ...
0
votes
1answer
41 views

Fairy lights dimming over time

I have had this cheap set of fairy lights for a few years. Powered by 3xAA batteries. Recently when they are turned on they start bright as they always were then proceed to get dimmer and dimmer ...
0
votes
1answer
103 views

Why are capacitors used parallel to transistors

In the circuit attached. There are two capacitors. One is parallel to "PWR LED". Although I understand it delays the turning on and off of the LED, why would you need that? Also, the other capacitor ...
0
votes
1answer
64 views

LED Driver with minimum input current and large LED current(peak)

I am designing a LED driver. Power source - 18V-42V (I can draw max of 6mA-7mA from source) LED string - 4 series LEDs of 6 strings in parallel ( total 24 LEDs) I need min of 200mA of peak/...
0
votes
2answers
144 views

Using resistors in a simple Led circuit

I'm using an 18650 (4.2v unknown mah) to power 14 leds (2v 20ma) in parallel with a 100ohm 1w resistor on each led. Everything has been running fine for 12 hours now with no problem. My understanding ...
0
votes
1answer
35 views

LED Lamps in series

I have some G9 220-240V 50Hz 24mA 2.8W LAP LED lamps. I assume that in order to power one I need a supply voltage of 220 - 240V AC able to provide 24mA, which is 5.28W. Why is it rated at 2.8W, does ...
0
votes
1answer
60 views

5 m, 5 V LED strip 20 A PS = Fire?

I've got a 5m LED RGB strip to go up the stairs and will be programming it with arduino. eBay link. They state 60 LEDs/m @ 18 watt/meter, thats 3.3 W per LED? It says current rating of 3 A, so that ...
1
vote
4answers
157 views

Turning on LEDs [closed]

I started a small project where I want to have three LEDs which are turning on gradually (in first step just one is on, one second step two are shining and then all three). I've tried doing it via ...
1
vote
4answers
111 views

74HC595 8x16led matrix arduino

I'm currently trying to learn how multi shifting is working and have therefore started a project where I wanna drive 2X 8x8 LED matrix with an Arduino. I have found it that I should work with the ...
0
votes
4answers
173 views

How do computers power so many lights on a keyboard?

Beginner here. I am working on building my own keyboard PCB, and I wanted to add a backlight for my keys. However, I've been reading methods of powering teensy little 3mm LEDs and it seems like an ...
0
votes
1answer
85 views

How to Convert NPN to PNP transistor?

I'm creating a water level indicator so I can turn on a pump when the water level gets too low. I have NPN transistors, but I would like the transistor to act as a switch that closes when the water ...
0
votes
1answer
54 views

Homemade LED flashlight [closed]

I want to make my homemade LED flashlight into an old utility light body. My plan is to use XHP70 LED from CREE (12V, 2,8A) and power it using 2S Li-Ion cells (6-8,4 V). My idea is to use boost ...
0
votes
1answer
53 views

Screen with built-in NFC

So I've started working on a small project (small at the moment) and I'm seeing some issues in my prototype plans, and I need your help with this. Short answer: I need a led touchscreen with NFC ...
0
votes
1answer
50 views

How to properly wire a 4.5V LED strip with 12V motors

I'm modding a Nerf gun (Rapidstrike to be exact), and I put a 3S Lipo in there with 1000 mAh. The circuit right now is a rev switch, trigger switch, switch behind the pusher, battery, pusher motors, ...
2
votes
1answer
80 views

Trying to wire up a couple dozen LED-lit toggle switches to an Arduino Mega

Update: Worked out a rough (I'm sure) schematic of the current idea for a smaller version of the circuit. A bit of info before the question; The Arduino has a current cap of 200ma across all I/O pins,...
0
votes
1answer
49 views

PIR sensor bypass for LED light strip

I don't know that much about electronics, but I was able to put together this PIR module: (original) and a LED strip and everything works just fine, when the PIR detects motion, it turns the strip ...
0
votes
1answer
56 views

How does this high amperage LED dimmer work while being so small?

I am trying to make a custom dimmer circuit for an off the shelf LED lamp meant for aquatic plant growth. I found a generic dimmer that many people (in the aquatic plant community) use, and am very ...
0
votes
0answers
46 views

RGB Illuminated Potentiometers

I'm currently designing a circuit using Alpha RV141F-40-20BL-B50K Potentiometers which feature a clear shift into which a 3mm LED can be inserted. My initial plan was to just fit a WS2812B ...
0
votes
1answer
71 views

Circuit to drive 3 LEDs that flicker independently

My basic requirement is that I need 3 higher-powered LEDs that flicker (like those little battery-operated candles you can get), powered from one power supply. The three LEDs should flicker ...
0
votes
2answers
74 views

Why do LEDs have/need positive and negative nodes to function whereas say resistors don't? [closed]

I'm very much a beginner experimenting for the first time with electronics, and I'm still trying to grasp the basics. On my breadboard, my LEDs have to be setup in a very specific way for them to work,...
1
vote
1answer
90 views

Why do I have to put my transistor after of my component, instead of before?

I'm working on a very simple project, where I want to control a 24V LED with my arduino. Since the arduino can't output that voltage, I have a separate power source, and use a transistor. This allows ...
1
vote
2answers
51 views

Switch Individual Lights In LED Series

I am working on a hobby layout that will have LED lighting for some of the elements. I would like to individually switch LEDs in series on/off. I used ledcalc.com to generate the circuit diagram ...
0
votes
2answers
107 views

How to run a 0.05A fan with a 10A source? [duplicate]

I am constructing a circuit to drive a powerful LED that requires about 10 amps at 12V. I also have a battery that happily supplies that. For obvious reasons, that LED requires a cooling fan, and I'...
0
votes
2answers
87 views

Current Flow indicator using LED

I want to build a simple measurement circuit for indicating the load on a little 12V pump. Assuming that the pump draws 200 to 2000mA depending on the load, how can I connect lets say 5 Red LEDs so ...
0
votes
1answer
61 views

Laser Diode and LEDs in parallel: LEDs don't light

I have a 3x1.5V battery pack (AA alkaline). It's fresh and with no load sits at 4.8/4.9V. In parallel, I have 3 LEDs, each with their own resistor. That works fine.. I can also switch in a 5V laser ...
0
votes
0answers
22 views

Getting the right configuration of an HC component with an LED

I am using an 74HC299 shift register and would like an LED on each of the 8 outputs. The LED I chose is the SML-LX1206YC-TR. I have a 100ohm resistor in series with each of the LEDs and each are ...