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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15 views

Connecting microcontroller

I'm trying to glow an led using a microcontroller and switch. I have programmed it to blink Every 2 seconds.when voltage comes from PB1 switch gets tuned on and led . Circuit diagram is shown here. ...
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1answer
28 views

LEDs in parallel, strange current consumption

I just wired a blue LED on a breadboard with the anode to an Arduino Uno's 3.3V rail and the cathode to a 220 ohm resistor to ground. Then I measured the current consumption using my Fluke 87-V and it ...
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62 views

I guarantee this one will be fun - Need help putting several circuits together into one

So I did my best to annotate the schematic with what I'm trying to do. Where I'm really running into trouble is past the output of the 555. This is basically a control circuit for a camera's ...
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0answers
36 views

LM3915 VU Meter Not working properly

I built a LM3915 (Waiting for LM3916 to arrive) VU Meter based on Sparkfun's tutorial https://learn.sparkfun.com/tutorials/dotbar-display-driver-hookup-guide Problem is, when I plug the power, only ...
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2answers
200 views

Toggle two different LEDs with one T Flip flop

Imagine we have one green LED, one blue LED, power supply and resistors and grounds. We also have a switch. Can we toggle between the two different LEDs when the switch is pushed? If the blue LED is ...
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1answer
51 views

Purpose of T flip-flop in this circuit (LED)

In this circuit I try to toggle a LED on and off when a switch is pressed. Given the nature of the T flip-flop, when the switch is triggered, it toggles the clock and since T=1 always, it ...
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3answers
60 views

Can I get constant current at the output of a buck convertor (to drive a LED)?

I want to drive a LED with a buck converter circuit as shown in the schematic below. In order to keep the circuit simple, the system will run open-loop (i.e.; there won't be any voltage or current ...
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2answers
76 views

What should be the value for the resistor for this circuit?

Sorry for this silly question but I am not from an electronics background. I am trying to build a very basic circuit with npn transistor to detect a certain water level. I am assuming the resistance ...
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2answers
249 views

LED that emits light in different direction

Is there such a thing as an LED that emits its light horizontally ("to the side") when mounted on a PCB instead of the ususal "up" direction? If so, what are these called, and do they use the same ...
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30 views

Two Sided Push Button Latch

so I have here a push button latch that is tried and tested and that works beautifully. But I need help making a variation of it that will switch between two circuits instead of just turning one ...
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3answers
144 views

Bike light blink speed adjustment

I am trying to construct a circuit to control an LED in a bike light kind of circuit. This circuit must be designed so that a button press can change the current setting of the light. So for instance ...
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0answers
68 views

Detecting two metal items touching

Basically I have a simple circuit with a LED connected to a metal ring. I want to attach another metal ring to make the LED turn on. The problem is with the second ring it cannot have anything ...
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58 views

Why is LED doubling the frequency of the pulses?

I hook up an Arduino pwm pin with a certain frequency to a scope and I observe puls frequency as f. Then I hook up an LED in parallel to signal and gnd and the frequency becomes 2*f. I tried with ...
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2answers
50 views

Do LED and photodiode rise times matter for time-of-flight (TOF) measurement?

Do I need small rise times of an LED and a photodiode/APD when considering time-of-flight measurement? Given I know rise time of both diodes I am always able to count time of flight by subtracting ...
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1answer
37 views

Additional current source for large LED-7-segment-display

I have two sets of LED-7-segs. Each with 4 Digits, all 4 inch tall. One set CC, the other CA. Combined they consume some smooth 1.68A / 1.4A according to the data sheets. That is manifold the ...
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0answers
49 views

Power micro LED's from 5 Volt USB

simulate this circuit – Schematic created using CircuitLab I'm working with this set of LED's: Link here: 30 Ft Led wire I measured the draw for the entire string at about 170 ...
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2answers
145 views

Voltage not dropping in circuit

This schematic shows the circuit that I'm trying to build. At the moment I'm not using V2, as I'm having a problem with V1. From my understanding the diode should drop the voltage by about 0.7V, and ...
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0answers
39 views

How does this 2 LED flasher circuit work? [duplicate]

I understand the capacitors hold the transistor open or close, but I don't really understand how it "toggles" to flash the LEDs.
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1answer
49 views

LED strip segments Parallel vs Serial

I have 5050 RGB LED Strip and an RGB controller (Something like this ...
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1answer
91 views

9v battery to parallel 3v LEDs - burnout

I'm having an issue in a simple (n00b) LED circuite - ended up burning out a couple of LEDs due to some mistake I'm making, but can't figure out what the error is. I've got a 9v battery, trying to ...
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1answer
55 views

Buck and Boost drivers for LED

Many of the newer bike lights use LEDs. Although I understand basic electronics it has been some years since I learned electronic theory. Although I understand the basics of buck and boost drivers I ...
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4answers
464 views

Turn a transistor on when any one of nine LEDs is on using an LM3914

I'm wanting to turn a transistor on when any LED from LED2 through LED10 are on with an LM3914 in dot mode. Basically, I want the transistor to be normally off until at least LED2 begins to light ...
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1answer
19 views

Ambient Light Sensor + Comparator

So I've been looking at options to create a way of controlling whether a flash will fire based on the amount of light in the surrounding environment. Early note: Everything has to be surface mount ...
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1answer
71 views

Make three respective LEDs blink with an LM3914 in dot mode

I'm trying to figure out how to make in the below schematic, LEDs D2, D3, and D4 blink respectively while the LM3914 is in dot mode when their on state occurs. Basically this would act like a warning ...
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1answer
57 views

How could this GPIO-controlled LED status blinker be improved?

I'm building a simple circuit to drive an LED status indicator in a project built around a RPi. The circuit takes its power from the same source as the RPi and is connected to one of the RPi GPIO ...
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3answers
90 views

Driving 48 LEDs with 1 Single Current Source

I need to drive 48 UV LEDs for UV paint curing system. (LED: 3.5V, 20mA) I found a simple current source, modified it, set the current to 20mA. The voltage on 3 leds is 10.50V (3 x 3.5V, exactly what ...
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3answers
96 views

Momentary\Pushbutton Latch Switch

I'm trying to make a circuit that will latch on\off with a pushbutton. This is what I have, but the LED just stays on even though the current shows the latch is working. Thoughts? Thanks :)
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2answers
47 views

Low voltage cut out switching for a 6v input SLA to 5v output circuitry - or alternative ideas

I am currently modifying a wireless video door phone system with remote door release system, for use with a walking frame, for my elderly mother in-law, who lives alone. The 7"monitor runs a 5v 1a DC ...
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1answer
73 views

Charger light circuit [duplicate]

I have a charger light. It gets charged by 220V AC supply. It can light 5 LEDs. I know that it needs to make the supply 220V AC to DC of lower voltage nearly 5V to 10V. Then it can charge the small ...
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2answers
71 views

Do I use a 5V 2A or 3A DC adapter to power my 2m (6.5ft) WS2801 LED strip?

(Please excuse me if my English is bad) I recently purchased a 5m LED strip, but I only need to power approximately 2m (6.5ft) of the 5050 RGB LED WS2801 strip, but I'm afraid that a DC power adapter ...
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2answers
76 views

Best way to make LEDs flash in time with a music source [closed]

Could someone suggest the best circuit to make LEDs flash in time with a music source directly connected to the circuit? BTW the circuit needs to run off batteries, I've seen circuits using TIP31 ...
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0answers
22 views

Custom IR LED controller for two independent strips

Is there a way to modify a controller with IR remote to control two separate led strips independently. Basically you have two strips, one controller, one remote and you can change the color|turn ...
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1answer
314 views

Why LED screens have to twinkle?

I was researching in psychophysic on optic experiment and I stumble upon my laptop manufacturer'screen specs. There is a 60hz refresh rate with exponentially decaying lums intensity between each ...
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1answer
44 views

Generate PWM signal based on 555 for Meanwell LDD driver

I am using a Meanwell Led Driver LDD-1000H. It has a single pin for PWM input for dimming. I have seen many sketches using the 555 to dim a LED but in these cases the LED was part of the circuit. How ...
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3answers
105 views

Need help with an LED flash circuit

I joined just because I'm having sort of a dilemma. I need to design a flash circuit for a tiny SMD based project, and I have a way of doing it, but I want to see if I can make it better and I haven't ...
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1answer
60 views

Capacitors vs buck/boost converters

I'm trying to drive high power LEDs with a laptop power supply, and wondered if I should use resistors to limit the extra current, or something like this to limit the current. If I did use that ...
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3answers
117 views

Smart ways to control an LED ladder?

I have two sets of LED ladders (12 in each ladder, so 24 LED's) that I want to control from my microcontroller. I don't have enough inputs for 24 LED's (and want to make it scalable), and the ...
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2answers
33 views

Usage of WS2821

I got a buck load of WS2821a, and I was wondering, can I use it for something else than driving LEDs? TechSpec: http://www.world-semi.com/uploads/soft/140305/1-140305102109.pdf Can it be used for: ...
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0answers
21 views

Piranha LED board connected to USB charger [duplicate]

Can I use this Piranha Light board to connect to a 5v power source like a USB charger? Do I need something extra (more than an USB-cable)? And can I connect more boards to the same circuit? (New to ...
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2answers
62 views

Problem with a circuit of an controlled variable voltage source

I have this circuit, it should regulate the output voltage between 15V and 0V. But the output I get when I simulate it is between 2V and 3V, and when I implemented, I burned zener diode 1N4734A. ...
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4answers
172 views

DIY small light pipe

I need a small (3 cm), 90° angled lightpipe to redirect a 0.5cm LED. I'm looking for a DIY solution using common materials I already have at home. (Even if it won't redirect all the light it is still ...
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1answer
98 views

Adding more LEDs to a current regulating circuit

I am modifying a current regulating circuit that was designed to power three LED lights (see figure below). The circuit is designed to maintain current through the LEDs at 1A. The LEDs should be off ...
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0answers
148 views

Integrated LED + Resistor + Transistor

Most designers when are controlling an LED have to make the same old circuit of Vcc -> Resistor -> LED -> Transistor (you need the transistor in case your ...
2
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3answers
173 views

Rule of thumb for LED Ballast Resistor

As well all know, using an LED without some sort of current control is a bad idea. One of the most basic types is a simple Ballast Resistor, paired with Ohm's Law. Based on Vin, Vf, and the desired ...
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1answer
72 views

Hooking up two voltage regulators for more power?

I have two LM317's, which I am wiring up as a current source for two high power, 10 watt LED's. The 317 can operate @ 1.5 amps maximum, so I plan to build two of these circuits. The problem I am ...
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2answers
35 views

Sum toroidal transformer outputs

I`m planning to buy a toroidal transformer for driving an LED. The LED needs 36 V and around 1 A. I found a toroidal transformer which has a 230V Input and two 18V 0.83 A Outputs. Can I simply sum ...
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2answers
84 views

Choosing an SMD LED size

I am designing a PCB an need an LED on it. I'm going to direct the light from the LED using a light pipe, so I need it to be as bright as possible. The question is what size I should use? All the ...
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1answer
97 views

LED's too dim. Wrong resistor?

I'm a halloween tinkerer, and I have these UV/Blacklight flashlights that I use in my decor, but they eat batteries like crazy. They start going dim within an hour or so. So, since I already have ...
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2answers
151 views

Use 555 for additional 40KHz PWM in Arduino

I need to transmit infra red signals using IR LED from my Arduino device. The IR signals consist of PWM 40 kHz periods and "silence" periods of various length (typical IR remote signals). I know ...
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2answers
106 views

Is there any notification system that can turn on a LED pulse?

I have an idea, and I searched if it exists and didn't find anything. I'm a live sound Engineer, and many times my musicians want to call for my attention, and I'm distracted with other sound things. ...