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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16 views

LED glowing when the driver's ground is cut off

I made a simple circuit with a premade LED driver (Recom RCD-24), analog-dimmed by a MCP4921 DAC, which is controlled by a 3.3V microcontroller board. You can see the schematic below, Q1 is unrelated ...
3
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2answers
84 views

The Transistor Menace - Questions regarding an Arduino rgb LED project

I've been browsing this forum and the internet now for a couple of days and what I thought would be an easy side project turned into a (for me) quite complicated matter. I'm planning to build a mood ...
2
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3answers
111 views

BJT Driving an LED - Above or Below?

I will freely admit that I am mainly digital when it comes to electronics, so may help explain my confusion (that or just general incompetence). I am getting review feedback on a design, and one ...
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0answers
40 views

Concerns About Solar Charging Tree House Lights

I'm Building a lighting system for my tree house with 4 LED work lights I picked up at the hardware store. I want it to have solar charging and be operable via one switch. Theres alot of background so ...
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0answers
32 views

Circuit with 12x3w Led

I have an 19v adapter and i tried to built a circuit with 12 3w leds and I connected them 3leds per parallel stripe. But when i turn it on the resistors heat too much and if i leave it more than a few ...
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5answers
318 views

Pulsing an LED with no series resistor

I have a basic circuit using a BJT common emitter which I have constructed to pulse a red LED on to use as a strobe with 1us ON time (@12V) and plenty of time to cool down (<< 1% duty cycle). ...
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5answers
110 views

Does a led determine itself current load? [duplicate]

If I use a power source rated at 2.5v and 1 amps for power a standard red led , what should happen to led? Does it get burn for the high current value or not?
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2answers
72 views

LED resistor calculator wrong?

Planning to use a green LED (forward voltage 2V, forward current 30mA) on a 12V circuit so using as resistor calculator (led.linear1.org/1led.wiz) I bought a 390 ohms, 1W resistor. However after ...
4
votes
8answers
710 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 ...
0
votes
1answer
46 views

BJT driven LED lengthy fall time

I am designing a circuit for a strobe amplifier and am having some difficulty with the LED emitting light for longer than expected. I am measuring the light out of the LED with a photo receptor ...
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2answers
39 views

PNP transistors and processor pins

On the diagram below, there are 4 PNP transistors. When RA0 is set to HIGH, then current flows from +5V through RA0 to GND and from +5V through 7 segment display, then through (for example) RB0 (if ...
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2answers
90 views

Is it possible to figure out the specifications of an electronics piece without datasheet?

I'm brand new on the "electrical engineering" scene with my Arduino and I have a question about random electronics. I've been taking apart some old phones, salvaging LEDs, motors and speakers, mostly ...
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0answers
24 views

Which kinds of electrical testing to be done on Emergency piezo Hooter/Buzzer which works on 12V DC?

I have designed 12V dc Emergency Buzzer/Hooter. I want to know which specific reliability testing must carry out on the same before mass production? Also for the same rated voltage of 12V DC which ...
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0answers
39 views

Powering high power LEDs [closed]

I want to power some high powered LED (R2) with this circuit. I would like the LED to be on for about 1 minute and they discharge C1 via R2. When C1 charges SW1 is open and the LEDs are off. When ...
0
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0answers
62 views

Controlling the luminosity (flickering) of 2 sets of 12V (in-parallel) lamps connected to external power source, via a PWM pin

I have been playing the last few days with the Arduino mic, and must say it does open a fascinating world. One very basic project I have been doing, with the help of various online tutorials, is to ...
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3answers
211 views

Max voltage vs current for LED

There's some basic flaw in my understanding of how LED's or diodes in general work so hope someone can help and forgive the simple question. So generally when one has an LED in series with a ...
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0answers
60 views

Led lights in series no resistor [duplicate]

Hello can I wire up 5 white leds in series with no resistor to a 9v battery. What are the advantages and disadvantages to doing it this way, or should I put a resistor on every led. Also where should ...
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0answers
75 views

Can I make an RGB LED Strip turn on white by default?

I have just bought one of these http://goo.gl/1dm5CZ (5050 RGB LED Strip with IR controller), mostly for fun, but hopefully with a slight practical application as well! It is to go in the back of a ...
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1answer
72 views

LED driver configuration

Can you identify any inherent problems with the following LED driver circuit? simulate this circuit – Schematic created using CircuitLab Ignore the part numbers as they are just for ...
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0answers
53 views

Powering LEDs from an ATX PSU

I've been thinking of replacing my ugly chandelier with 5 meters of LED strips. While browsing webshops, I've seen cheap 12V 6A (=72W) LED power supplies, which would be just about enough to power the ...
2
votes
2answers
226 views

Is this 12 volt LED circuit correct?

I found this "Plant Grow LED light" circuit on the Internet and I wanted to know if: (Please don't feel pressured to answer all my questions. You can just answer a few only if you like.) this is ...
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votes
2answers
87 views

How to Design a schematic for 8-LED Logic Circuit and Turn them on in pairs? [closed]

I'm trying to design the schematic of an 8-LED logic circuit and turn them on in pairs according to the following sequence: 1 - 8, 2 - 7, 3 - 6, 4 - 5, 5 - 4, 6 - 3, 7 - 2, 8 - 1 ,i used ...
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votes
1answer
43 views

Binary Counter IC Counting Incorrectly

I'm currently trying to use 74HC163 in a project, and it appears I have it wired up correctly, but it counts in a very strange sequence. I wrote down the sequence as follows: ...
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3answers
93 views

Do standard white LEDs produce a full spectrum of light?

At places like Radioshack, small (and sometimes large) LEDs are available that are labeled to be "white". This is a link to a Radioshack page for such an LED: ...
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3answers
94 views

LED Resistor Choice with changing voltage

I'm planning on adding leds to a small quadcopter which runs on a 1s lipo battery. I am planning on attaching the leds straight to the battery rather than the regulated voltage the main circuit board ...
0
votes
1answer
75 views

280LM Led Headlamp needs FCC certificate?

Do I need FCC certification for my 280LM Led Headlamp with 1800MAH Lithium battery which is rechargeable only via USB? More details: Watts out: 3W Lithium-ion Cells: 103450 Energy Content:1800Mah ...
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1answer
49 views

Using IR Emitter and detector incorrectly

So I bought this from radioshack and tried to set it up following this tutorial. The problem is, the red LED lights up and when i try to interfere with the connection, nothing happens. When I remove ...
0
votes
1answer
41 views

reading led requirements

I'm still pretty new to electronics and I bought an led from radio shack that said 12vdc add max. It also said 20mA and 1.5mcd which says is it's intensity. Is 12vdc the max volts and 20mA the minimum ...
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votes
2answers
66 views

run LEDs with cellphone charger

I wanted to run LED bulbs with a mobile phone charger/adapter ( input: 220v AC, output: 5v 350mA, nokia). but the LEDs become very hot & I'm afraid they may burn. i don't know the ratings of these ...
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vote
1answer
124 views

Trouble with very first circuit

I'm building an assembly that will drive some infrared LEDs. Although the final product will use three, I'm just playing with one for testing purposes at the moment. The spec sheet for the LEDs I'm ...
4
votes
1answer
108 views

Transistor Choice for LED Control Circuit

I just completed an introductory course in digital design. During the course I designed a circuit for driving multi-color LED's with an automotive application (for a personal project). The following ...
4
votes
2answers
553 views

Can I use LEDs without PCB?

I recently purchased LEDs on ebay that were supposed to come attached to star PCB (as a heat sink). The items I received are just the LEDs (no PCB). They are listed as 3W LEDs, with a forward voltage ...
0
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0answers
30 views

Why does this make the LED flash green? [migrated]

I connected an arduino to an RGB LED, but it isn't working. This is the circuit: I have double-checked everything to make sure that the ports were correct, but it still flashes green when I make ...
2
votes
1answer
70 views

Shift Register Programming with 8 and 16 bit drivers

I built up a test circuit using 2 74hc595n shift registers to control a total of 16 leds with success. In the interest of saving space, I designed my circuit board to use one STP16CP05MTR shift ...
0
votes
2answers
105 views

Different LEDs in parallel

Are there any special considerations I should pay attention to, when I wire multiple LEDs in Parallel? I am doing a project with a 100 LEDs in parallel. Each LED could be a different color, and each ...
0
votes
1answer
50 views

Switch LEDs in Series

I have an array of 20 10V LEDs @500 ma. I would like to connect them all in series, as my driver is capable of this, but control 4 sets of 5, having any set combination on or off. I could do this with ...
2
votes
2answers
64 views

Can I solder high power 1W LEDS on aluminum with 60/40 solder? [duplicate]

I want to create my own light source using high power 1W LEDs. Can I solder high power 1W LEDS on aluminum with 60/40 solder? Here's a picture of a potential heatsink
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0answers
18 views

How to make arduino show cpu usage with 10 leds? [migrated]

So i want to make arduino show my computer cpu usage with leds, for example if 10% then 1 led will light, if 50% then 5 leds, if 80% then 8 leds...
1
vote
1answer
61 views

How can I increase the multiplier of a voltage doubler circuit using IC4049?

I replicated a voltage doubler circuit from this example I found online: ... and as expected, I am getting 12V from a 6V input. I would like to increase the multiplier to more than 2x, but I am ...
0
votes
1answer
158 views

How can LEDs sense darkness?

I've read in the Make magazine that LEDs can sense darkness. How should I use it in a breadboard circuit? Is it possible to read the ambient light level and send it to the computer? How does this ...
0
votes
1answer
69 views

LED with A/C Input

I've got a little problem. I've got a house with a lit address number. All the homes in the subdivision have the same device. Doggone thing is wired up 27 volts A/C and is wired for two ...
0
votes
1answer
47 views

20VDC LED Illumination

I'm looking to build a simple test circuit, where I can get an LED to illuminate when it senses 20VDC or above, and to remain off if it is sensing any less.
0
votes
3answers
67 views

Driving one LED from audio signal only with pnp transistor

How it's possible to turn on/off a single LED with the left (or right) sound channel of an audio jack and a pnp transistor. Everywhere npn transistors are used. Like here: Driving LEDs from audio ...
0
votes
3answers
95 views

Lumen difference between CFL and LED

How much watt I need for LED bulb to get the same amount of light produced by 32 Watt CFL bulb? So, comparing lumen is the right way to find out the difference between these two light source?
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votes
1answer
49 views

what is the value of resistor used for 4 digit 7 segment 12 pin display?

refer circuit http://www.instructables.com/id/Arduino-4-digit-7-segment-display/ .Here no any resistor is use is there any need to connect resistor for a b c d e f g .And is there any alternative for ...
0
votes
2answers
156 views

Does this RGB LED really need 220 ohm resistors per color?

I have an arduino kit (5v) and instead of just following their simple instructions I want to know why they are using certain resistors for their RGB LED's. The RGB LED that comes with this is ...
-4
votes
1answer
45 views

connecting more than one LED to same battery increases volts, mah, or both?

Not really sure what happens to the current when doing so. If a high intensity LED with a wide voltage, say 9 to 20 volts, will the LED draw more current as you increase the voltage/gets brighter?
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2answers
58 views

AWG gauge for 10W cob leds and common ground

Two questions: How can I calculate the appropriate AWG for a 10W cob led (~12V DC at 900mA)? Suppose the appropriate AWG is 22, and I want to use a common ground for them (for the purpose of this ...
0
votes
3answers
136 views

Why does this big button require 12V DC for an LED?

I'm looking at the Spark Fun Big Dome Push button. The spec on the page (and other places selling it) says that the LED is 12VDC. Does this mean that I need 12V as a minimum? Am I not able to just ...
0
votes
1answer
53 views

Running 6 LEDs off 3s (12.6v) and 4s (16.2v) battery

This may be a very simple question but I want to run 6 LEDs on a PCB and I know I can run them simply off a 12.6v 3s battery but if I want to run a 4s battery 16.2 then I will need some sort of ...