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.

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26 views

General wiring questions: high power LEDs, relay and microcontroller

I think I understand the Raspbery Pi GPIO pins and most of how this diagram below works, at a high level at least. First question, it's not clear to me exactly how the middle part with the ...
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1answer
34 views

Common cathode LED resistor with 4017 decade counter

Is it possible to use a common cathode resistor for all 10 LEDs with 4017 decade counter? I try it but only the first LED (output 0) lights up. EDIT: I got it working. My wiring was wrong. I use a 9V ...
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1answer
70 views

Resistance to use for a LED circuit

I have extracted a strip of 6 LEDs from a LED strip that has these caracteristics : LED Quantity 300leds Input Voltage 12V Power 72W/5M Cuttable Every 3LEDS Package 5 ...
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0answers
52 views

Led grow light problem [on hold]

I am making an LED grow light. I have 72 3W LED on heat sinks on an aluminum board wired in series. I have 5 50W constant current LED drivers to power it. I have tried wiring the drivers every way ...
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2answers
70 views

Does an LED TV that is displaying “black” emit enough light to trigger an LDR?

I would like to monitor a digital sign to make sure it stays 'online' - the setup is a Raspberry Pi connected via HDMI to an LED TV. I have seen some general linux discussion about polling ...
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1answer
55 views

Sequential circuit with more than 10 LEDs

I need to build a sequential LED circuit that will have more than 10 LEDs in a sequence. The LEDs should blink only one at a time. I know I can do 10 LEDs with a 4017 decade counter easily, but I dont ...
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2answers
64 views

Building an RGB LED module [on hold]

I'm a beginner in electronics, read a few books, have solid understanding of the basics. I would like to make an LED Screen Project I need some quick advice for. I want my RGB LED Matrixes to be ...
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6answers
1k views

How to drive 128 LEDs

I now have a PCB with 64 UV LEDs on it and I use this to expose other PCBs. I have a serial resistor for each LED which produces a lot of heat and consumes about 1.3 A at 12 V. I am now considering ...
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0answers
37 views

Simplest signal level/clip LED indicator?

I was looking to modify a circuit that would take a signal from a guitar, impedance-match, amplify and bias it so that it would be readable by the ADC of a micro-controller, effectively based off this ...
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1answer
55 views

Create large Arduino powered LED sign

For a project, I need to create a large display (most likely an LED matrix) that can be controlled via Arduino. Large means probably somewhere in the neighborhood of 3' by 10". I intend to use an ...
2
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4answers
143 views

Pulse Detection

I have the following simple LED driver. I over drive LED much beyond its current limits in terms of current. (50mA @ 25% duty cycle with an RMS current around 12mA). In this case the circuit ...
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0answers
58 views

Need a battery OR wall wart circiut [closed]

I am just learning electronics so please bear with me ... I have a plastic model that I will be lighting with a (for me) complex circuit. All the youtube videos (model makers that light their models) ...
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1answer
64 views

LED nightlight solar panel battery charger

I have a nightlight with a 25mA 3.3V LED powered with four 1.2V rechargeable AA batteries using a 48 ohm resistor. How do I hook up a 4.5V 1w solar panel (Radio Shack #2770048) to charge the batteries ...
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1answer
73 views

Lighting an LED when a capacitor is fully charged

I've been messing around with electronics lately and I wanted to make a simple circuit that lights up an LED when a capacitor is fully charged. I know that something could be done with a diode or ...
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1answer
117 views

Do these LED's have a constant current driver built in?

I bought these LED's of eBay and connected them all (5) in parallel with a 4.7Ohm series resistor each. This should have given me a total current draw of 1.7A. However, when I measured it, I was only ...
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1answer
26 views

Optic fiber with partial diffusion

I've seen a partially diffusing flexible optic fiber used in several places, but I can't figure out what exactly to google to find the stuff. Does it have a name? I'd like to stick leds to each end ...
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0answers
68 views

Combining LC filters

I would like to add an EMI filter to a high power LED driver. The datasheet of the driver suggests an LC filter for the power line as shown below. However I would like to use more than one driver ...
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2answers
251 views

LED still shines when MOSFET is off

I have the below circuit and when I turn off the MOSFET (Logic 0 at gate vg) the LEDs (LED1 and LED2) still shine with a small intensity. When I replace the LED with an incandescent lamp (car lamp) ...
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1answer
60 views

LEDs and buttons - ready made [closed]

We want our first semester students to learn programming and see the results of their exercises on a LED matrix. Unfortunately, we can not start soldering with the guys in the first week, so we are ...
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2answers
63 views

Controlling LEDs [duplicate]

I am needing to control about 75 Infrared LED's individually of each other (can turn each on and off) through the use of the program LABVIEW. Originally I was thinking of using multiplexers to ...
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2answers
51 views

Running up to 40M (130Ft) of WS2801 IC LEDS

After many hours of searching the internet for information and gathering what I could, I have run into my final problem that I am having trouble finding an answer for. I have 40 Meters (130) Feet of ...
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0answers
28 views

best way to energize loads in a sequence

I need to energize loads in a sequence, and for certain time periods which would be preset, or a time period selected by the user of the equipment. In my project I have a digital display, water inlet ...
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2answers
89 views

Power supply for 144 LEDs in parallel?

I appreciate any help as I try to figure this lightbox project. I need to wire up to 144 3V (built-in resistor) LEDs from flickering tea lights (normally battery powered). Not sure how many to wire ...
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1answer
49 views

Are LED drivers inter-switchable?

MR16 type LED bulbs need their halogen counterparts' driver replaced due to low power consumption and they require an "LED driver" that can deliver the necessary wattage. On the other hand, LED ...
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3answers
372 views

Creating led sequence without microcontrollers

I'm new to electronics and I can work only with transistors. I'm trying to create a circuit that performs action like this: Let's say I have 10 LEDs. When I supply power first LED lights, 0.5 sec ...
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2answers
95 views

How do I control several individual LEDs with Arduino?

I am working in a book store and I have the task of making an indication of a book place in the Library Cupboard with LEDs. I need to control about 300 LEDs with Arduino. What is the optimum way to do ...
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1answer
60 views

How to tell a common cathode vs a common anode full color led?

Is there a way to visually tell if it has common cathode or a common anode on a full color LED?
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2answers
72 views

Thermocouple Simulation Test Circuit and Voltage Comparator Circuit

I have a challenge that I would like to share with you. (at least a challenge for me) The resistor R8 (10 turn potentiometer) can be adjusted from ~0 to 1K Ohm to output voltages from 3mv to 30mv. ...
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2answers
81 views

More advice desired on my Model Railroad Building light controller circuit

Building is built in O Scale (1/48) and has 40 rooms that are lighted independently (masked out from each other with walls) Rooms are lighted with White LEDs. The rooms will light one at a time (but ...
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2answers
131 views

wiring leds for car brake lights without throwing warning lights [closed]

Im working on led tail lights for my vehicle. the standard bulb is a 21w 12v bulb. what i need to try and figure out is whether or not i am able to recreate this same load using leds without a load ...
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1answer
67 views

555 timer flashing led circuit

I just have a question about this simple circuit or example: http://www.555-timer-circuits.com/flashing-led.html. I just don't get 1) why do they use 9V battery to power a single red LED light. 2) why ...
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2answers
101 views

Turn on an LED when power is lost with a relay

A friend of mine has just finished his race car but is having fan issues. What I want to help him do is setup an LED that turns on when the fans have lost power. Often the fuse blows. I would assume ...
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2answers
110 views

Will my 12V power supply ever burn these IR leds blinking at 38kHz even without a resistor?

I'm new to electronics, my background is mostly on the software development side... so go easy on me, as this might be a really stupid question. I just want to be sure what is safe to assume and what ...
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1answer
65 views

Alternative LEDs Blinking circuit(Analog) Help

Can someone explain the operation of this circuit, I understand the basics of the BJT and its modes, but most of my confusion arises when there is some-sort of feedback loop in the circuit, my thought ...
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2answers
58 views

Powering SMD 5050 strip via LM2596 DC/DC converter

I decided not to order / use the power supply typically sold with SMD 5050 kits. I heard a lot of explosion stories regarding those dodgy stuff. I want to make my own (power supply to drive SMD 5050. ...
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1answer
59 views

driving LEDs via a PI a attiny and TLC5940 (validation) and possible powering issues

at the moment I am planning my first real (big) electronics project. I want to build a LED lamp, that can be controlled by a RaspberryPi (for e.g. programming a binary clock or changing the brightness ...
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0answers
28 views

Precise way to compare Color Quality in Monitors [migrated]

I don't know where to publish this question, but here seems like the best place to do it, so here it goes: I couple weeks back I bought a retina-macbook pro and I love it. To go along with it I bought ...
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1answer
86 views

What kind of amplifier to use?

I'm driving an LED from the output of an optocoupler. Example, I'm trying to find surface errors on a sheet. When the sheet is flat the average output voltage is around 2.45V (based on the circuitry I ...
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1answer
84 views

3W LED light (15x 3w LED)

I've started to play with LEDs but every time I feel I've come to understand them, I get confused again... I have attached my plan so far, I was wondering if any of you could give me some advice!
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5answers
148 views

How does the Brita LED work?

Specifically, I'm talking about this product here... Brita Faucet Filter It has an LED that blinks when the water is running. It blinks red, yellow, or green to indicate filter quality (maybe) - but ...
2
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2answers
82 views

Random flashing on WS2812B LEDs

I'm trying to drive a strip of WS2812B LEDs with a Beaglebone Black(revC). Because the LEDs expect a data signal at 5V and the BBB outputs at 3.3V, some sort of level shifting is required. However, ...
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1answer
50 views

12V battery choices (powered LEDs and piezo buzzer)

I need to power two 12 V LED lights (1W - forward current @ 0.083 A) and a small piezo buzzer all in parallel (unsure about the current, tried to measure it with multimeter, but get nothing...). ...
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2answers
60 views

On/Off DC power indicator [duplicate]

I am pretty sure that this should be simple but the answer is eluding me. Basically I would like a simple 12V DC circuit that lights one LED (red) when a power switch to a pump is off and would ...
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1answer
143 views

Reducing LED flickering

I am using a PIC18F452 micro-controller to generate PWM with ADC. The PWM output is connected to an LED through a MOSFET. There is some flicker occurring. How can the flickering be reduced? can you ...
2
votes
4answers
274 views

LEDs are burning. Cannot figure out why

I have a lamp that has LED driver producing 35 V (actually lamp driver says 16 - 28 V, but I've measured 35 V). On the lamp I have 7 LEDs (originally 5 + 2 I've added) with heatsinks that have burned ...
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2answers
68 views

Calculating discharge time of 12V LED light powered by AA batteries

I just want to check up my assumption on power consumption of six 12V LED lights in parallel connection. So I powered it by 6 AA (E91 energizer) batteries. The LED's ideal forward current is 80 mA ...
3
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4answers
124 views

Why do most PWM LED displays and backlights operate at a relatively low frequency?

All around me are a bunch of electronics: digital clocks, my laptop, a refrigerator, a dimmable flashlight, and more. What they all have is perceptible flickering of their displays due to PWM, ...
2
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1answer
179 views

Optimizing LED Project

I'm working on a project the will use 20 white 3mm LEDs that I harvested from a 154 LED Christmas light string. I plan to use a 9 volt battery for power. What's the optimal wiring schematic? Series, ...
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4answers
159 views

Wire for project with 9 volt battery

I'm working on a project that powers 20 LEDs with a 9 volt battery. What gauge of wire should I use? A couple of LEDs are in series with a 180 ohm resistor. Then each pair are in parallel.
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1answer
62 views

Prototype for 8x8 RGB LED display [closed]

I am planning to build a small, very low-resolution, 8x8 RGB LED display, which would be able to display a video (some kind of colorful visualization, lo-res) or a picture from PC via DVI or HDMI ...