Led Definition and 450 Threads

I just purchased a breadboard and components because I love tinkering with things. It's not for a class or anything more of a hobby, but I just needed some advice on a simple hello world like blinking led circuit. I have gotten down the basics of lighting up leds, and my second project I wanted...

I have an ackward question. I've been trying to device a circuit to reverse the pattern of a LED. Let me give you a quick rundown of my situation and my goal. As it stands now. Imagine a an alarm system. When activated a LED is lit 24/7. When a switch is triggered the led will blink...

I am building a 2 to 4 decoder with 7408 And gates and need to put LED's on the output as indicators, active high. 2 questions 1. Would I put a current limiting resistor in series with the LED to ground or put the resistor and LED from the gate output to Vcc? 2. The LED draws 30mA at 2V...

Ordered this: https://www.amazon.com/dp/B000OGABWM/?tag=pfamazon01-20 Got this warning Warning "Always wear ANSI approved safety goggles when using this product. Before using this product, the user should read the operating instructions to understand everything about this product...

Hello, You've probably already seen sites about "LED throwies" which are little circuits made of An LED A small 3V watch battery A Magnet Some Tape The idea is that you make these and then stick them to different things and the glow and are pretty. Anyway, with that background...

Hello all, I recently became interested in building an LED lamp as a gift for a friend. I have a good understanding of technology, but I have only a small understanding of electrical engineering. I have researched and understand how to build an actual LED lamp where I would have all the LEDs...

Hi. New here. I'm not necessarily a newb at wiring I've used solder before and have wired up other simple wiring diagrams. I'm hoping someone can help me with a task I'm looking at doing. I'd like to wire up a set of LED taillights. 48 red led's in the brake circuit and about 24 in the turn...

Your opinion, please. Does one of the two variations of this circuit offer a clear advantage, or is it a wash (see attached)? This indicator circuit turns on the LED below 11V (set by the zener). The LED cathode must be at ground (it is actually part of a tri-color LED with a common cathode)...

Hi, i am trying to design a circuit, where i am trying to light up an LED long enough based on my pulse signal. Here is what i am trying to do. a 10us pulse(every second) --->74HCT04 buffer---> (RC circuit)----> LED. since this is a 10us pulse, i want to make sure to light up the led for...

Are there any specific infrared LED's that have a narrow "beam width" when emitting? If not, does anyone know of a way to constrain it? A lens perhaps? I would like to control the beam width over a distance of about 2 ft. I might need to go with a laser emitter... Any suggestions...

Hi I would like to know if there is a sensor available in the market that would help control the intensity of light given out by a white LED, taking into account the light coming from the surrounding ambient light. As an example I am trying to implement a project in which I would have to control...

Homework Statement If an LED is used in an optical communications system, explain what would happen to the temporal spread caused by material dispersion in the fibre as the LED is cooledHomework Equations (having trouble using the latex equation editor, sorry) I know that the temporal...

Alright I need help. I am not electrically inclined so figure this is the best place I could have come. I'll make this as simple as possible. I have: 1 Red 5 mm LED with specs 2.6V - 28mA * 10mcd 1 Green 5mm LED with specs 2.1VDC - 25mA - 6.3mcd 9V battery as source What I need. Need...

I have a small screwdriver which has a small LED in it. When you stick it into something like an outlet, and hold your finger on the other end, the LED lights up. Today though I held both ends of the screwdriver and the LED lighted up. This confuses me tremendously... Doesn't that indicate...

Hi, I'm wondering how to drive front and rear lights off one dynamo. See diagram for current setup. Lights are hooked up to dynamo in parallel. The LM7805 and LM317 are voltage regulators which drop the voltage from 12v to 5v and 10v respectively. Currently only the headlight works, the...

Sorry.. I know this is really simple.. I have 3 composite video signals, and switches to select between them. The switches I have are SPCO, so I can't just use another pole for the switch voltage. So, I need a way of detecting the video, and this switching on and LED. At first I...

Hi all, quick question here. As part of a sophomore seminar class, I have this little task to complete. I currently want to send a series of 4 bits through an IR LED that will reach a GaAs photo transistor. What I'm doing is using a shift register to load in the binary value (via a parallel...

I've posted on here a few times concerning the electrical problems I continue to encounter for my video installations. And yet, here's another one. If anyone remembers, I posted a month back or so concerning the use of an audio signal from a home audio receiver to open and close a small...

Theoratically a LED can last for 100,000 hours, but how can i prove that this is true? I've found out that the malfunction of a LED is caused by the degradation of the active region in it, but how can i determine when it is going to malfunction?

This image shows the ground supports of the bridge before the collapse: http://www.wmur.com/2007/0802/13805989_240X180.jpg taken from: Nation's Bridges Face Immediate Inspection. Fifth Victim Found; President Bush To Visit Minneapolis UPDATED: 9:20 am EDT August 3, 2007...

I want to replace a single flashing red LED on my motorcycle alarm with something more ominous to ward away potential hooligans ;) I've searched for flashing & pulsing and ramping LED circuits using Google and came across this forum, so hopefully someone here can help me :) What I would like...

I bought three LEDs, three 1k ohm resistors, and some wire. When I bought the LEDs, I made the person show me that they worked. He connected the negative end of the LED to the yellow wire, and the positive part to the resistor, which he then connected to the black wire. The LED lit up. As far...

edit: problem solved. Thankyou berkeman.

Hey all, I posted this thread just under a year ago, but I never followed up with replies. But I've suddenly become interested in finishing it up. Because I want to power several LEDs (say 5 @ approx. 30mA), I'll use a hefty transistor for Q2 (say TIP31) and a relatively lightweight BC108...

I'm hoping this is the right forum for this question, I've never been to this part of PF before. I've taken up some interest in working with LED lights but I'm slightly confused with how to build the circuits for them. I'm told you need to put in a resistor to keep the LED safe from high...

If President Nixon had been imprisoned for breaking the law it would have set a precedent that would have deterred Clinton from lying to Congress and Bush and Cheney too.Isn't it about time leaders got locked up for law breaking or else what is the point of the law?

I don't know when does a capacitors and the transistors switch and turn the other off considering the voltage across them...well, on other words, don't know what makes the LEDs do the flipflop thing...HELP

We routinely test "continuity" in our phone lines by holding a red/green LED to our "tip" (hot) and "ring" (cold) which lights up bright red if all is well with the AC signal. A bridge rectifier added to the mix let's the "green" shine; reversing the LED wires on + and - will make the...

Hi, I am looking to build a basic spectrum analyzer (if that is what you would call it) out of some LED lights for a car stereo. Basically, I want about 8 - 10 bars (for different frequency bands), and I want them to jump up and down to the music, giving it a direct feed off of the car...

Does anyone know if there is such a thing? I need a bar-graph LED with a FF built-in. The only ones I could find on digikey is a regular 10-diode LED, but I need something that would latch or hold that value until the enable changes... I could use a regular one in combination with a D-FF, but...

Hi, I'm looking for a very cheap uP start kit that I can practice c language and perhaps assembly language on. I want to light up led's and stuff like that. Can anyone direct me to a good url to find one I can purchase. I'm interested in the software (compiler), etc. too. regards...

There's a lot of products with LED's these days. However I was wondering why a light made with LED's is done with an array on LEDs instead one large one. Can we not make a large one? Is it possible to make a large LED but it's actually more efficient to have several smaller ones? Any...

Hello. Does anyone here use and LED light for their desk? I am a college student and spend a lot of time at my desk reading. I get pretty bad eye strain from reading so much. I am thinking about getting one of these LED lamps. Also, does anyone use any other type of lamp that is better...

I was given this circuit and it was supposed to be an LED dimmer circuit that changes its brightness (gradually) when the switch is closed/open. I was told that the darlington pair was supposed to "smooth-out" the changing brightness of the LEDs. But here are my questions about the circuit...

Hello Genius guys, I am beginner in the field of electronics engineering.Well i am planning to make LED TRAFFIC SIGNAL /i know the wroking of 555 timer ic iknow the working of Multiplexer,Demultiplexer,encoder ,decoder. well can u tell me the circuit diagram of LED TRAFFIC signal 4 way...

For want of a nail, the Kingdom was lost!

I have a scooter, which looks like this one http://img47.imageshack.us/my.php?image=gsra3eng9zq.jpg and i have two 7.2 volt battery packs to run two 12 volt led neon sticks that would sit underneath the deck and light up and look cool :rolleyes: . Well this works, but i think the voltage...

I am getting ready for my lab tomorrow and one of the questions is this: ok, here's what I think: since current flows from anode to cathode and in first case LED's anode is connected to the pull-up resistor, so there's current through it and it's going to light. In second case, wouldn't it...

I have held the dream for a long time of LEDs being controlled by an audio signal. You know, when the music gets louder, the LED gets brighter. Not just 'fully on' or 'fully off', but different levels of brightness. However, I don't know how to build this circuit. I think the audio signal...

hi i have fixed a simple circuit for lighting up a led.i have included a potentiometer. as the led is white i know that the voltage drop of the led is around 4v.when the potentiometer is at min resistance the voltege drop is actuallu around 3.8v.the problem is that when i turn the potentiometer...

hi i want to use a microphone connected to the base of a transistor.yhe transistor should work as a switch . it should turn on with a sound to the micro phone. does anyone know what voltage the mic can produce?what kind of microphone do i need and what kind of transistor?the circuit is designed...

I am wondering this because my car has very nice looking speakers when viewed in the light, however in the car they don't get much light and you hardly even notice. LEDs are cheap lights...so I was wondering if there is any way I can use these, maybe even run them off the sound signal itself...

Can someone please help with the following question. Thanks Develop a program for the Motorola MC68HC11 using the THRSim11 simulator software. The program is to display a number 10 digits long, one digit at a time, on a single 7 segment LED display. Each digit will be ON for 1 second and OFF...

Hello Can someone please help with the following question. Thanks Develop a program for the Motorola MC68HC11 using the THRSim11 simulator software. The program is to display a number 9 digits long, one digit at a time, on a single 7 segment LED display. Each digit will be ON for 1 second...

Does anybody know why illuminating an LED with a filament lamp would produce a voltage in a simple circuit with just an LED and voltmeter? I'm guessing it's related to the photo-electric effect, but I have no idea what is actually going on. If any of you guys could help me out, or point me in...

hey guys, I have been looking to make a outdoor led washlight for a long time now. I am not very experienced with electronic circuts but I can understand the basics. I am planning to have 30 leds, 10 each of red green blue. I want to control the three different colors with a potentiometer...

I am working on a project for my electrical engineering lab class, and am interested in learning how to build a led spectrum display. I'm looking at very basic. I want 3 sets of LEDs, one for the high, one for the mid-range, and then one more for the low. Any clues where i can find a design...

Conventions ! The experiments on the interaction of a conductor carrying a current and a magnetic field conducted by Oersted more than two hundred years ago , have resulted in conventions that unfortunately are still colouring our perceptions of how exactly the electromagnetic field around...

Hey folks, I've been watching the first two LOTR movies a lot, in anticipation of the 3rd one to come out in December. Lately I've been noticing all the imagery that Led Zeppelin borrows from that trilogy, and I am now listening to "Battle of Evermore", which mentions the ringwraiths. That...

Being as it's summer and I don't have school I've been spending everyday -- and, recently, every night because I haven't been sleeping well -- reading. Well, I had an idea the other night, so I wanted to see what everyone else thought, and find out if I came up with something novel or if I'm...