A LED is a light emitting diode. Lighting a 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.

learn more… | top users | synonyms

-1
votes
0answers
25 views

Dim 12V or 24V DC LEDs with GPIO [on hold]

I am interested in dimming a set of 12V or 24V DC Cree LEDs. I actually need several dimmers, so I want to buy the dimming unit instead of trying to build them all myself. I would like to use simple ...
2
votes
1answer
54 views

Toggle battery powered LEDs

I am helping to build a costume prop that has four LEDs lights on it (1 white and 3 amber). This device is worn on the wrist, so space for power is limited- a 9V battery or something that will fit in ...
5
votes
3answers
339 views

Will 74HC595 as LED sink damage LED when pin goes high?

If used as a LED sink, what happens if a 74HC595 pin goes high? Might the LED blow? I expect that when a pin is low, current will sink and the LED will light. What about the opposite condition? ...
2
votes
1answer
254 views

LEDs flash at the same time and not one at a time

As you can see on the illustration below, I have a voltage supply (a keyboard made of two piezo elements) with two terminals. Each one drives one LED, but since I've added a buzzer in parallel with ...
0
votes
1answer
55 views

USB lights up simple circuit but not coin-cell

I have 13 adafruit LED sequins in parallel hooked up to a CR2032 coin cell. This cell is also hooked up to an adafruit Gemma board (Arduino-like board using an Attiny85). Pads D0 & D1 on the Gemma ...
1
vote
1answer
49 views

How to choose what a power supply to drive 2 x 10watt RGB LEDS?

I'm trying to figure out how to determine what power supply I should be using for different types of LEDs for this and future projects. I have 2 x RGB LEDS: Forward Current: 350mA Forward Voltage: ...
-5
votes
0answers
54 views

current voltage calcultion of LED stacks [on hold]

Sir, please provide the details on how to calculate current voltage of LED stacks for ITI students(INDIA)
1
vote
1answer
56 views

Controlling various Arduinos with Android

I have an upcoming project which requires me to use about 8 different Arduinos, probably more. They all perform a light show which turns off and on various LEDs at different timings to simulate a ...
0
votes
2answers
85 views

Timed LED circuit with ATX PSU, help

I want to make a circuit that turns on and off the light (LED) of a given time (eg. on 9 pm and off 6 am). I also want it to be adjustable. My idea about the design: I will be using an ATX computer ...
4
votes
3answers
436 views

Extending LED length

Completely new to electronics, I've just begun to play with an Arduino. I was wondering, if I wanted to make an LED sculpture, what is the correct way to extend the legs of each LED so that they stand ...
1
vote
2answers
64 views

Creating a “virtual” LED display

I have a small project and I would like to have an LED display, just for the sheer fun and look of it. However it would be too expensive for me to make (I would like to use RGB leds) and I would need ...
-3
votes
2answers
113 views

How to make LED lamp (220V 50Hz input) circuit by using 1 watt LEDs? [closed]

I think to make LED lamp circuit by using 1 watt LEDs (300mA and 3.6V). How to make circuit. But I can not use transformer.Because size and cost of transformer is high). Input single phase, 220V,50Hz ...
0
votes
0answers
26 views

Calculating power draw for LEDs and driver (TLC5941)

I am designing a backlit keyboard with 61 white LEDs. These will be individually driven by a TI current limited PWM driver (TLC5941). LEDs: 61 x Osram LCW JNSH.PC (Datasheet) Drivers: 4 x Texas ...
1
vote
1answer
55 views

12V LED strips in series with a 24V power supply?

I am purchasing 50x - 1Meter / 12V / 72 LED /Rigid SMD 5730 strips directly from china. I don't know the LED manufacturer, nor the resistor being used. (yes, this is a gamble) The strip is one that ...
1
vote
1answer
132 views

LED driver circuit help needed

Please help me figure out which inductor to use from this datasheet. Sorry - it's in Chinese as this is an Asian sourced IC and not sold in the US. (Use google translate if necessary - but, the ...
0
votes
1answer
83 views

Create poolball patterns with LEDs on snooker (pool / billiards) table

I'm building a system which places dots on a snooker (pool/ billiards) table for where the balls should be placed, how can I obtain colours like brown and black from LEDs? Is the best approach to use ...
0
votes
1answer
42 views

Laser activated switch using a photo-transistor

I would like to make a laser activated switch using a photo-transistor or an LDR, by which I can switch off the lights in a room from a long distance. I just have to point the laser and it will detect ...
-1
votes
2answers
53 views

Can a few inexpensive components light a white led from 2 AAA alkaline batteries? [closed]

Please help with finding an energy-efficient LED driver circuit for 2 AAAs(all the way down to 2V), for example for this LED: ...
-1
votes
0answers
34 views

LED strip flashing to music [on hold]

I'll give you the backstory: A few weeks ago, I used a popular enough circuit to create LED lights that flash to music. The circuit I used as a template is the first image in the imgur album ...
0
votes
1answer
112 views

How can I power this LED Matrix?

I'm controlling a 16x32 LED matrix with an Arduino and have it wired correctly (I think) but I'm having trouble with the power. I tried to follow the instructions from Adafruit but was unsuccessful in ...
1
vote
3answers
150 views

3 Watt LEDs in Series - Using constant voltage Source

I have searched everywhere for an answer to this question but I think its probably so simple that no one has felt the need to answer it. Basically I have 20 x 3 Watt LEDs and have a 80W Constant ...
1
vote
2answers
78 views

Identify high current LED Package name

Based on another question recently asked, this package is very common, used in high current LED applications (0.5W ~ 3W). The package includes the led chip, lens, heatsinking, but can vary in light ...
1
vote
5answers
111 views

Could somebody tell me which resistor to use with this LED

I went to my local electronics store and asked for a powerful LED because I wanna make a small flashlight. They gave me this thing, but the problem is that the stores in my area don't have any ...
1
vote
1answer
81 views

Red light therapy LED spotlight

What's the easiest way to mount a bunch of surface mount LEDs into an array or spotlight? There are a bunch of very interesting new papers on red light therapy for a variety of conditions. I want to ...
0
votes
1answer
71 views

problem with LED Matrix circuit

I want to create a LED Matrix circuit with 74HC595 shift register and 2n7000 mosfet. The schematic is as follows. I have mentioned voltage levels at various points. All the control signals of ...
0
votes
2answers
106 views

Night activated LEDs

I want to use a photo resistor to make a circuit like this But instead of light causing the led to turn on, I want darkness to cause the led to turn on.
-2
votes
2answers
74 views

Is it possible to run 230V LED - or flourecent “spiral-tube” - lightbulb with a 9V battery?

I would like to power a 230V LED lightbulb with a 9V battery. I assume I'll have to dissect it... Surely there must be some sort of power-converter and rectifier from 230V-AC to something a lot ...
2
votes
4answers
267 views

Alternating between two LEDS using BJTs

I would like to control the output of two LEDs with a single pushbutton. When the button is open, D2 should be off and D3 should be on; when the button is closed, D2 should be on and D3 should be off. ...
0
votes
1answer
116 views

Most lumens per watt

I recently started designing a pcb for flashing lights I want to use in a pavillon at festivals, garden parties and the like. Now my question is, can anyone tell me which kind of LED that has the ...
0
votes
0answers
64 views

Poor output efficiency of SEPIC supercap driver

I'm attempting to drive a high power led (3.6V, 700mA, nominal power 3W) from a 5.4V 3F supercapacitor via a SEPIC (see this question). While I don't have any strict design requirements, a running ...
0
votes
1answer
43 views

bluetooth headset with LCD and memory

I was wondering if it is possible to create a bluetooth device which would have a LCD screen and some memory (1kb) for making and receiving calls. From my research ( and I am far from an EE, but ...
-2
votes
2answers
58 views

What is current forward (if) of an IR LED

I see a lot current forward on datasheet, but I don´t know the difference from the "normal" current. EDIT On this datasheet, I saw a If (current forward) of 100mA and then on page 3 it states about ...
2
votes
1answer
100 views

Beam Angle vs Viewing Angle

I am looking at the product specs for an IR light and see that it has: Beam Angle: 50 deg Viewing Angle: 25 deg What is the ...
-1
votes
2answers
53 views

Complex LED drivers/circuits [closed]

Throughout my travels I've seen these very complex circuits that incorporate ICs for "i.e. dimming applications" that are included in designs with buck boost converters, etc. What makes LED driving ...
7
votes
5answers
806 views

Question about resistors and LEDs

How can I find the right resistor to make 50% brightness in an led? I know how to find the right resistor to get the brightest but I'm wanting to find the perfect middle.
1
vote
1answer
59 views

What kind of RGB LEDs are these?

I bought these RGB flood lights cause I liked the LEDs I saw in them and I was wondering what kind they are so I can just buy the LEDs and not the whole flood light.
0
votes
2answers
87 views

Can I use a LED Driver to control a Solenoid?

I have on order an LED driver and I want to use it as a simple 12v DC output to control a Solenoid Valve. The Driver says Constant Current & Constant Voltage. I obviously don't want 1A pumped ...
0
votes
1answer
43 views

Color Changing LED Circuit upon power on

The circuit I plan to make will have 3 RGB LEDs in it and what I would Like is for it to change colour each time it turns on to a random colour. I'm a beginner level so any help will be greatly ...
0
votes
0answers
51 views

How to power Common Cathode RGB LED

I'm trying to figure out how to power a common cathode RGB LED. The setup I have below does not work. I assumed power would flow to R, G, and B, and there would be a white light; but nothing. Would ...
11
votes
2answers
984 views

High frequency blinking LEDs and sensor for that

I want to make LEDs blink rapidly. (more than 1000 blinks/sec., faster is better) First, I am curious that the common off-the-shelf LEDs have a capability of blinking with such a high frequency. ...
0
votes
1answer
74 views

I have a not working LED driver IC

I'm currently using a boost mode constant current LED driver IC LM3424. I used a MCU to PWM dimming the brightness of the LED, and schematic of LM3424 part is almost the same as it in LM3424 ...
1
vote
2answers
175 views

Transistor Ohms

I've built the circuit in the schematic below to control my TV, the D1 and D2 LEDs are the two mini LEDs from this IR Extender: I've cut it below the female headphone jack and I'm using my ...
-1
votes
0answers
67 views

Maximum Ohms for IR LED and transistor

I bought a cheap IR extender and I'm trying to use the small sticky cases to control my TV using a Raspberry Pi. The extender has two "heads" with a small IR LED in it and they were connected to the ...
1
vote
2answers
75 views

Messing with rgb leds and have a question

I have some LEDs that I'm wanting to use in a project. I would like to know what's the best resistor I would need to get the most light out of the 3 different colors using a 12v source. I've measured ...
0
votes
0answers
35 views

LED bulb that works on both 64 volt DC and 110 AC

Can anyone advise on a reliable/cost-effective way to modify a screw-in LED light bulb so it will run on an AC power supply that has a battery backup where DC is provided in backup mode (this is for ...
2
votes
3answers
68 views

Shift Register turning on Transistor for LED Cluster

I have a question concerning using 74HC595 with two transistors to power a LED matrix. My goal is to make an 48 x 8 LED matrix using a cluster of 5 LEDS per unit (as opposed to only using one led as ...
1
vote
1answer
119 views

Two or more different regulators connected to one battery

I want to make batteries provide power to both a micro controller (Raspberry Pi) and a 4x4 LED matrix. A simple circuit diagram is shown below. (only one LED is drawn in the fig. But regard it as LEDs ...
0
votes
1answer
74 views

Constant current LED driver min / max current rating explanation

I currently have a 150-1500mA led driver that I sue to power a 30W LED. Driver has adjustable maximum current pins that I can use to change to match the maximum current. I have it set to 1050mA. I am ...
0
votes
1answer
56 views

How is possible to connect 3x 100w led lights to a 300w led driver?

Could you explain if is possible to connect 3x lamps of 100w to 300w led driver? The led driver specification is: constant current, 27-36v, 9A. The lights: 1x, 27-30v, 3.5A, and 2x, 30-36, 3A. So, ...
0
votes
3answers
77 views

Need assistance in identifying wire

I'm working on a LED project similar to the one in the picture, and I need to identify the black wire that the arrows are pointing to. What are those called? Here is a picture: