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An LED is a light-emitting diode. Lighting an 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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2answers
72 views

No battery rechargeable led light

I want to make a tiny led glow for 10 minutes once charged by induction. I want the entire PCB not greater than 20x20x5mm. Is it possible? I have come up with the following circuit, I don't know if it ...
-9
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0answers
45 views

Turning On every Led one by one when switch is pressed or when switch gets open [on hold]

I am using four bicolor LEDs (red and green) and I want these LEDs to glow from red to green one by one when switch is pressed or when it gets open. I think it can be achieved using counter IC or ...
1
vote
1answer
53 views

Help needed in understanding this LED chaser ciruit

Here is a circuit called LED chaser that I found the other day. I watched some videos on Youtube and saw that its function is to blink the LEDs in some kind of sequence: https://www.youtube.com/watch?...
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2answers
89 views

Voltage doesn't add up in LED circuit

The circuit consists of following: simulate this circuit – Schematic created using CircuitLab And video on this link. Summary: When there is no current flow on the circuit, supply voltage is ...
0
votes
1answer
41 views

Led as an input photodiode [Arduino AVR]

I’m trying to use a LED as a light sensor(input) connected to a Arduino Nano. I connected the led with the Anode at digital pin 8 (PB0) with a resistance of 56 Ohm and the Cathode at an analog pin A0 (...
0
votes
1answer
35 views

How to test 3528 smd LED

Using my DMM and the diode selector, the SMDs 3528 in a brand new Led bulb does not light. I used this method to test the classic "round" leds but in this case it does not work. What seems to be wrong ...
-2
votes
1answer
27 views

Convert a 100-277V dimmer to 1-10V [closed]

I'm trying to use the following dimmer: https://www.smarthome.com/switchlinc-dimmer-insteon-2477dh-remote-control-dimmer-dual-band-high-wattage-white.html with these lights https://www.eledlights....
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3answers
427 views

3mm different color LED resistances for bright light

I am trying to power a number of different color LEDs with a 5V wall-wart power supply able to deliver 2 Amps. I tried to make them light with equal intensity and I like them to be bright. (They get ...
1
vote
2answers
140 views

DC-DC switching converter PCB design

Recently I had a problem with noises in my led driver. I realized that my PCB design was terrible, so I redesigned whole PCB following common rules. Could you take a look and check if my new design ...
0
votes
2answers
50 views

Over-voltage on a current regulator

Let's say I have a current regulator, or a LED driver, set at 4V that can sink 20mA. If I connect a white LED rated 20mA at 4V to it, then everything is fine. But what happens if I replace, in the ...
2
votes
2answers
69 views

Measuring junction temperature of LED tape?

My boss at work wants me to figure out a method of measuring the junction temperature of an LED that is part of a reel of tape. Unfortunately, there is no datasheet for the LED modules themselves, ...
2
votes
3answers
70 views

Reduce flickering on cheap 220v AC GU10 LED Lamps

As I am unable to find exact answer anywhere, I am looking for some help. First of all, I'll explain the current situation. I have a freshly built appartment where noone ever lived before. We decided ...
0
votes
1answer
59 views

Transistors as Switch and Amp to control LED strip

I am controlling an LED strip based on audio input from my phone. I am having some good results, but not exactly what I want, and my ignorance of transistors is holding me back (I'm a Mech E major ...
-1
votes
1answer
73 views

Can anyone identify the IC for LED controller in the picture?

Recently my LED surgical light has been having a problem with its controller. I opened the controller and found this board with two ICs: One is a Shift Register (74HC595) and the other has no markings....
-1
votes
0answers
37 views

How to with 12V LED driver by 12V [closed]

I do a digital clock. 6 Digi by 7segmant common anode 12V Can I get driver?
2
votes
5answers
161 views

What's the difference between typical and maximum forward voltage for an LED?

The datasheet for some LEDs I'm considering lists the forward voltages as 2.7V typical and 4.2V max. (I'm looking at the "warm white" version.) In the past, I've only ever looked at the typical ...
1
vote
1answer
63 views

I have an LED with no specs, but it does have a resistor. I want to double the voltage

It's one of those "stick anywhere" lights that look like a household switch. It's powered by 4 AAA batteries and has two-2 inch LED strips connected in series with a 3 ohm resistor(looks like a 1 watt)...
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votes
2answers
54 views

High power LED array

I’m designing SLA 3D printer and I need to design UV LED array for LCD screen backlight. Preliminary design is 5x3 (5 parallel lines with three LEDs in each). All LEDs will be soldered on PCB. The ...
0
votes
1answer
29 views

How to turn on LED with PMOD on FPGA

I have a 12 pin PMOD interface on my Nandland Goboard FPGA and I would like to turn on an external LED with it. I can do it on my using pins 5 and 6 which are GND and VCC but I can't figure out how ...
1
vote
2answers
67 views

How to sense touch on a diffusing sheet?

I want to build a combined diffused light and touch-button around 3x3cm. LEDs could be diffused with e.g. a polycarbonate sheet or diffusing fabric, and touch could be sensed e.g. through capacitive ...
-1
votes
0answers
26 views

D-Battery LED Lantern Aluminum Foil Repair [closed]

I have this LED lantern that wasn't working after I changed the batteries to a fresh set and, in the process of troubleshooting, I discovered that there was space between the positive lead of one of ...
0
votes
1answer
51 views

STP16CPS05 Sink Driver External Resistor does not change output current

Have a 10 x 10 LED array sourced with CD74HC154 Decoder/Demultiplexer to PNP Transistors (rows) and sinked with STP16CPS05 Sink Driver (columns). This is driven with an Atmega328P. Rows and columns ...
2
votes
3answers
58 views

Constant Current LED Driver with Raspberry Pi Zero W

I have a 12 V DC source that I'm wanting to run a Raspberry Pi Zero and a couple of 3 W IR LEDs. I'm not using the Pi to control the LEDs in any way. The LEDs are just to provide lighting at night ...
0
votes
2answers
58 views

Unexpected current reading when powering LED from ATmega328p IO pin

I would like my LED to run at 40mA (max current for ATmega328p IO pin). The LED datasheet says that 2.2V is max forward voltage. I am trying to calculate which resistor to use. According to the ...
1
vote
3answers
60 views

Illuminate an LED when a ground switch is open

I have a switch that connects the negative side of a solenoid to ground when closed and I need to have an LED that is illuminated when the switch is open. I was thinking of using a transistor to do ...
1
vote
1answer
51 views

Dim a LED array through PWM on power supply or output enable?

I have an 8-LED array driven by an 8-channel source driver (TD62783AP) controlled from an 8-bit shift register (74HC4094). When it comes to dimming the LEDs using PWM, I came up with two solutions, ...
1
vote
1answer
473 views

4 channel optocoupler [duplicate]

I was designing a dual H bridge board which uses some logic signals to drive 8 mosfets. Initially I was using 8 optocouplers per board which was really annoying to wire up. after a bit of searching, I ...
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votes
2answers
66 views

Can't power controller and LEDs with chosen power supply (works in one project but not in other)

I'm currently running into a rather confusing problem... I'm trying to power a strip of 60 WS2812 Leds and an NodeMcu/ESP8266 board. The supply I chose is a 5V/4A supply. This one to be precise: ...
0
votes
1answer
59 views

Strange thing with 5mm LEDs and variable PSU

I have 3 standard LEDs (not COB just the tiny regular ones used in circuits with an Anode and Cathode in epoxy lens), I was just testing them today doing random things with them: 1.9v - 2.1v = red 3....
0
votes
2answers
69 views

Photoelectric smoke alarms leds harmful? [duplicate]

Hi I needed some serious information for the safety of mine and my family’s, I just moved into a new house and I’m removing the smoke detectors because they are really yellow and look old. I was ...
0
votes
0answers
61 views

Connect wire to earth when PC power led is on

I am trying to make a mod to a computer case. What I want is that every time the computer power led lights, another cable connects to earth. Something like this. I read the motherboard outputs 5V for ...
1
vote
2answers
29 views

What is the correct current in the datasheet for the LED-Matrix?

If I understood correctly the maximum DC Forward Current for one LED is 30mA (Page 2). So if I wanted to drive an entire column (5 LEDs) I would need 5 times the forward current. If I don't take the ...
1
vote
2answers
118 views

How can I turn an LED on only at 24 V ± 1 V?

Is it possible to make a circuit so an LED turns on at a specific voltage? My requirement is to indicate whether 24 VDC is available at the pcb or not (used as a power supply indication.) I want the ...
13
votes
3answers
278 views

LEDs no longer bang - or whimper!

I volunteer at a club to teach Arduino programming to teens. As part of that, of course, I talk about voltage, current and what not to do. My prime example is taking an LED, putting it directly across ...
2
votes
2answers
53 views

Using 74HC154 with LEDS current resistor

I am using a 74HC154 to control 10 LEDs in a design. Since only one LED will be on at a time I wanted to use one resistor rather than a resistor per LED. Is there any difference between the two ...
0
votes
2answers
41 views

Bicolor/RGB 2x2 LED Matrix?

I'd like to make a bicolor/RGB LED matrix, for this example I'll use 2x2 in size. Suppose I have this matrix arrangement, without any wiring yet, only the LEDs: I want to make each LED programmable. ...
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votes
3answers
145 views

Mixed Colors LED project

Pretty new to LED wiring, so need a little advice, please. Project includes 16 LEDs in all, 4, different colors with, of course, 4 slightly different requirements: 4 Red, 4 Blue, 4 Green and 4 Yellow,...
1
vote
2answers
45 views

Why do people use a separate current limiting restore for each LED in a matrix? [duplicate]

This might have a really basic answer, but its been bugging me. In a lot of circuits where you are controlling a series of leds, circuits will be draw with a separate current-limiting resistor for ...
0
votes
1answer
86 views

Is it possible to use a raspberry pi to control these LED strips?

I want to control some LED strips (inside PVC tubes) with a raspberry pi. Is this possible? Where would I start? The problems are, I don't have a lot of info about the strips: LED Chip Model:SMD5050 ...
0
votes
1answer
34 views

Totally noob here,help me choosing the best method of powering led

First of all im sorry for the grammar because english is not my 1st language,so bear with me. So im trying to power up 100 0603 red smd led,its a generic brand and all data i could gather was its 1.8 ...
1
vote
1answer
50 views

Driving blue led directly from GPIO [duplicate]

While looking into the schematic of the Nucleo STM32F767ZI, I saw a blue led driven by 3.3V, which is the GPIO voltage of the STM32. The datasheet of this led specifies a typical voltage drop of 3.3V, ...
0
votes
2answers
43 views

AL5802 LED-Driver works on the breadbord, but not on its (seemingly functionally identical) PCB

TL;DR: I'm working on a project that incorporates (besides other things) two AL5802 linear LED-drivers in parallel. Unfortunately, I felt balsy and had my complete PCB made in China before testing the ...
1
vote
2answers
109 views

Op amp driving a LED oscillates, how to stabilize?

I have a simple LED driver circuit like this: simulate this circuit – Schematic created using CircuitLab The op-amp is OPA354 250-MHz, Rail-to-Rail I/O, CMOS Operational Amplifier supplied ...
-1
votes
1answer
43 views

Toggle between two leds [closed]

I am designing a circuit with not a lot of knowledge in electronics and I am close to finishing it. The finishing part remains. So, I have got a logic 1 or 0 from comp op amp and based upon that one ...
0
votes
1answer
37 views

Help Powering 2x10W LED using a 15v 1A power supply

Beginner here, trying to build a lighting using two 10W SMD LED'S. Please advise me for a better and efficient setup. Here are my specs. Power Supply DC 15v 1A LED specs: Input voltage 9-12v ...
0
votes
1answer
59 views

Cheap and powerful stroboscope: Turning a floodlight into stroboscope?

I would like to build a Stroboscope with the most cost-effective and less time-consuming approach. I would like to be able to control and know the frequency of operation, which should be at least of ...
0
votes
1answer
42 views

Read the state from an LED in a MCP23017

I read already this 2 questions: Read state from LED in another circuit Read the state of a 12v illuminated switch from an Arduino Uno and I can read the state in a MCP23017 controlled by an ...
0
votes
4answers
116 views

Toggle two LED status lights with two transistors

I have an input that is either floating, or grounded. The switch is fixed, it's either open or closed. Ie, I can't replace with a double throw. Here is the schematic / sim. If the switch is closed, ...
0
votes
2answers
52 views

LEDs + Constant Current Driver - Discharging the Circuit

I have a project where I made a series of high power Osram OSLON blue leds using custom boards on aluminium PCB. I just put 16 LEDs in series and joined them to an appropriate constant current supply. ...
0
votes
2answers
199 views

LED Hissing issue with circuits [closed]

I have just recently designed and manufactured my very first PCB with the goal of it being a dedicated circuit to my project. I developed an ESP8266 WiFi Mood Light, but the problems I currently face ...