Tagged Questions

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

0
votes
0answers
12 views

Normally closed SSR won't work with grounding out a magneto's primary to ground

I've been trying to find a device that will ground out a magneto's coil (primary kill wire) in a normally closed state without using a mechanical relay. I began to search for normally closed solid ...
0
votes
1answer
47 views

Photo transistor in parallel

I'm a beginner and trying to figure out how this circuit works (its a simple circuit that glows an LED when dark) : https://www.youtube.com/watch?v=eIGWWKThprI&list=UUhtY6O8Ahw2cz05PS2GhUbg#t=65 ...
0
votes
1answer
53 views

Where is the bin code/label of LED?

Recently I have purchased 150 LEDs from Digi-Key and expected bin code/label of the batch to be on the package. But I can't find it? Where do I find bin code/label information?
1
vote
1answer
89 views

Controlling 90 LEDs using one WS2811

I wanted to build a circuit where i would be able to control 90 LED's using one WS2811 and have a total of 60 WS2811. In this circuit I hope to connect 30 LED's per channel, there is no need for me ...
0
votes
1answer
52 views

ATmega8 LED blinking project not working properly

I am making a simple project using ATmega8 microchip. I uploaded this code to the AVR: ...
0
votes
1answer
44 views

Connecting a 12V DC power adapter to Arduino [duplicate]

I'm working on a school project and I am a total beginner on this arduino stuff. So, I bought this led strip at IKEA and used this tutorial to connect it and controll it with my Arduino. The thing is ...
1
vote
2answers
83 views

How to start LED wirelessly in a very compact and cheap module?

I have been thinking and researching about this issue for a while with no success. I am hoping someone can solve this problem in the community. I want to have many small modules each with a small ...
0
votes
2answers
97 views

Which component cannot handle the higher wattage?

First time posting a question, so hopefully I've stated all the required details. As the title is not very specific, here is an explanation of my project. I'm making a revised version of the ...
8
votes
3answers
1k views

LED strips: 46% resistive losses?

I recently bought these LED strips. They are supposed to run on 12V/72W and have 300 x the SMD 5050 LEDs on it. Schematic: simulate this circuit – Schematic created using CircuitLab The ...
0
votes
1answer
46 views

Arduino Uno R3 + Android multiple LED blink can turn on but wont go off

I'm new here and I have a question...I hope you could help me, any answer is more than welcome...so I am using an android app with switches to turn on and off 5 LEDs...I managed to turn on four of ...
2
votes
1answer
80 views

LED strip brightness and its measurement - did I get ripped off?

I recently bought two 5m rolls of red and blue LEDs for building an hydroponic lettuce light. Each of them is supposed to have the following properties: 300 SMD 5050 LEDS 72 Watts 12 Volts 4500 ...
3
votes
2answers
337 views

Does this linear current source driver deliver constant current?

I was reading on LED driver designs, and I have a question about the linear current source driver. In the circuit below, will D1 ever turn off when there is too much current through R2? In other ...
0
votes
3answers
70 views

Circuit to tune multicolor LED colors with a variable knob (rheostat?)

I am looking at getting some multicolor LEDs, which have Red Green and Blue inside of them. I'm doing this for space saving, rather than using 3 different LEDs--I am using just one. What I want to do ...
0
votes
0answers
33 views

High-voltage seven segment LED display driver problem

I've a circuit similar to THIS project, with a 74LS04 as inverters instead of 74HC54 (tested 74HC04 and CD40106 too) and ULN2003 instead of ULN2803. The circuit seems to work perfectly but when I turn ...
1
vote
1answer
28 views

Multiplexing problem with Arduino, MAX7219 e BJT

I tested the circuit below with an Arduino UNO, a MAX7219 and BC338. The sketch in Arduino is a chaser, so the leds should turn on in sequence. It consist of 7 segment (A-G) and two Digit (0-1). The ...
0
votes
1answer
47 views

Choosing a high-power LED Driver IC [on hold]

I need an LED driver to power one (or more) high-power LED(s) for a torch. Design requirements: Efficiency is paramount, since the power source is either a battery or a supercapacitor. Must be able ...
0
votes
1answer
60 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. ...
1
vote
1answer
48 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 ...
0
votes
0answers
72 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 ...
0
votes
0answers
41 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 ...
1
vote
2answers
210 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 ...
1
vote
1answer
56 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 ...
1
vote
3answers
63 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 ...
-6
votes
2answers
79 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 ...
3
votes
2answers
261 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 ...
0
votes
0answers
32 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 ...
1
vote
3answers
150 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 ...
0
votes
0answers
74 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 ...
0
votes
0answers
60 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 ...
2
votes
2answers
51 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 ...
0
votes
1answer
39 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 ...
0
votes
0answers
52 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 ...
1
vote
2answers
146 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 ...
0
votes
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.
0
votes
1answer
56 views

LED strip segments Parallel vs Serial

I have 5050 RGB LED Strip and an RGB controller (Something like this ...
0
votes
1answer
95 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 ...
0
votes
1answer
56 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 ...
1
vote
4answers
467 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 ...
0
votes
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 ...
0
votes
1answer
73 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 ...
0
votes
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 ...
0
votes
3answers
96 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 ...
0
votes
3answers
98 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 :)
0
votes
2answers
50 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 ...
-1
votes
1answer
76 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 ...
0
votes
2answers
74 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 ...
0
votes
2answers
79 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 ...
0
votes
0answers
23 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 ...
1
vote
1answer
315 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 ...
0
votes
1answer
48 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 ...