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Questions tagged [led]

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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16 views

310 watt light bar on 12 volt car battery [migrated]

I am currently looking at a 32 inch 310 watt LED light bar for my 2010 Honda CRV. The light bar I am looking at is https://www.amazon.com/dp/B07MCNYXFT/ref=cm_sw_r_cp_apa_i_JpKPDbTR3J8R4. The wiring ...
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21 views

HV9961 led driver: trying 170V led output

I face to some issue with my prototype based on the HV9961 (see picture). I replaced L1 by a 1.8mH power inductor and R1 by a 68k resistor. Those values came from HV9961 datasheet formulas for a 170V ...
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64 views

series connected capacitor

simulate this circuit – Schematic created using CircuitLab How does the capacitor behave here? I tried and the led flashed. Does the capacitor work like a diode after charging?
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96 views

Constant Current Drive for LED

I am going through the circuit as shown above. In such LED drive design (constant current), I am not sure about the role of R16 (2 ohm) resistor. Is it for transistor to have less power dissipation ...
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2answers
47 views

FET-based H-Bridge for bi-color LED

I've got a bi-color LED in a push-button that is red when powered in one direction and green in the other direction. I would like to control it from a Raspberry Pi GPIO pin, e.g. High=Red, Low=Green. ...
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51 views

IR Light Detector as MOSFET Gate

I would like to use an IR transmitter/receiver pair to detect when an object obstructs (or does not obstruct) the path between the the transmitter and receiver and illuminate an LED when the path is ...
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1answer
53 views

LED Matrix design without micro-controller

I am working on a project concerning the creation of a LED matrix (4 x 6) but without using a micro-controller. It will be powered by a 13V battery and the leds will be controlled by a switch. My ...
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447 views

Reverse Voltage?

Sorry, I searched but could not find (or maybe understand) and exact answer to my question. I am a carpenter, not an Electrical Engineer. My passion is building things (almost anything) and ...
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47 views

How to change polarity at 120V DC using DPDT?

I have a strand of LED Christmas lights. Each "bulb" has two LEDs - one is color and the other is white - the polarity on the string determines which of the two LED lights up. Pressing the button ...
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4answers
85 views

Why is 12V the standard for LED strips?

I am wondering why 12V is the standard voltage for LED strips (RGB/W) when each SMD LED whether it be 3535 or 5050 is usually rated for ~3V. A lot of energy is wasted as heat through the SMD ...
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24 views

Touch sensitive surface above leds

So I'm currently working on a box which should dim my lights based on a touch surface on top of the box. To indicate the light brightness I want to place a ws2812b ledstrip under a layer of white ...
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1answer
64 views

Use one 12V 30A timer for two separate 12V inputs?

I'd like to use the following timer, rated 12V 30A, but for switching two different 12V inputs at the same time and not having to buy and program two timers. But the timer only have one channel. One ...
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58 views

How to connect LED to output device to show the output state without any voltage drop so that it can be sensed by MCU?

I am using an NE555 timer to get output from one of my output device. The basic function of NE555 timer here is to toggle the output of my output device which was successful but I need to attach a LED ...
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42 views

Power on indicator

I have 12v battery that I hook up to the Internet modem when there's a power outage -happens frequently-, and so in order not to forget that it's hooked up when the power comes back. I need an ...
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49 views

Calculate spherical surface area of IR emitter

I have an IR LED emitter. It has a 20 deg. beam width. The total power radiated is 70 mW. I want to calculate the power density (mW/cm^2) at a range of 30 cm. How do I calculate exactly, the area of a ...
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31 views

LED Bulb Failure detection system

The below figure is the current system I am using and working fine. The only problem with this the bulb it will burnt out within short period of time. Now I want to to change it with LED bulb, but the ...
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44 views

replacing AN6878 led driver IC

I'm trying to replace the obsolete AN6878 led driver (logarithmic response, used for audio level indicator) with a modern and available solution. I'd like to keep the same functionality of the ...
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1answer
38 views

Driving parallel LED strings

I need to drive and dim 4 parallel LED strings. Each color (see below) dims separately. Another constraint is minimising the number of wires running from the light to the driver. Here are my options ...
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1answer
50 views

Simple blinking Led with control over both the pause rate and flash time?

I was hoping someone could help me understand a very simple approach to creating a flashing led. While many simple examples exist, I cant quite find one that allows me to control both the pause rate ...
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259 views

LED diodes as both diode and load for boost converter

I'm doing an LED project with a Cree CXB3590 LED that I intend to underpower to experiment with efficiency and learn about boost converter design. I've made a 5uH inductor with 14 gauge magnet wire ...
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26 views

Multiple LEDs, Multiple Switches, One Power Supply

I am working to design a circuit like the following where the power supply is 9V, and there are multiple LEDs to be potentially lit, and all are turned on or off either by a switch or by air pressure (...
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1answer
59 views

What are these LED power supply plugs called?

New LED lamps made in China have fancy new connectors and I'm searching for the IEEE official name (or whichever authority names them). I need to order male and female ends that can be opened to ...
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2answers
79 views

Infrared LEDs with minimal RED glow

I'm trying to find a 940nm SMD infrared led with minimal red glow at night. The TSAL6400 gets close to it, but it's still not completely invisible and not SMD. I've noticed IR leds have different ...
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1answer
54 views

Why can the IS31FL3731 only handle 32 RGB Leds when it can handle 144 Regular ones?

I am looking at using the IS31FL3731 IC in a project soon, but I am confused as to why the data sheet says that the circuit can only use 32 RGB LEDs when it can use 144 regular LEDs. The data sheet ...
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62 views

How to power multiple independent LED segments

I'm new with making electronics and I'm trying to make simple LED based binary clock. The problem is, that I don't know how to power it - I want to use 17 segments each containing 9 LEDs (153 LEDs in ...
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1answer
42 views

How to IR LED as half-duplex transceiver or just receiver?

I'm i need to capture IR signals in their raw form from IR remote to analyze them. Currently I'm doing it by connecting logic analyzer directly across led on the remote. I want to skip that step and ...
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29 views

Constant current converter for variable voltage source and load [closed]

Does there exist a device or circuit that can take a constant current device and output a current with a direct ratio to the input? Regardless of voltage. So a load that requires a constant current ...
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63 views

What is the off-white powdery material found at the base of GU5.3 light bulbs?

I've noticed most GU5.3 light bulbs, both halogen and LED, contain a granular material at the base. There seems to be considerable variation in how much of this powder is present, even within the ...
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1answer
34 views

Resistor power dissipation when driving optocoupler from ac mains

I followed this: https://learn.edwinrobotics.com/230v110v-ac-mains-detection-using-arduino-raspberry-pi-and-esp8266-thing/#Step2 With the exception that I used an LTV-814 that doesn't require a ...
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1answer
80 views

Driving NPN with Raspberry Pi

When driving an NPN transistor using the GPIO output on a raspberry pi I assume no protection is needed on the GPIO side of the circuit? So nothing would really be needed beyond this to drive the ...
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1answer
100 views

Locomotive directional lighting

I would like to have three led lights on the front and rear of a locomotive (garden railways) so 6 leds in total. These are (LED, bi-colour, 5 mm, red + yellow 3 Pins - L-59EYW). The part I'm ...
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53 views

24V signal to drive led

I have a PLC which gives 24V DC output. I would like to drive an external LED using 24V. Is this the correct way to drive an led? Which is the right method let me know any changes needed. simulate ...
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1answer
36 views

Correct way to add LED in front of SSR?

Looking at at adding a simple LED indicator in front of an solid state relay. Not sure if its more correct to put it in series or use two different resistors as shown in the example. The indicator LED ...
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22 views

How does one match irradiance to Luminous Intensity in Candela of source?

A light source has an Irradiance of about 1.6 W/m²/nm at wavelenght 385nm and an LED: Peak Wavelength 385nm Viewing Angle 30 ° Luminous Intensity 80 mcd If this light source shines on a ...
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133 views

How is powering an LED with a 9 volt battery possible without burning the LED?

I used a 220 ohm resistor with a 9V battery and the LED works fine. However, most sources say the forward voltage in a red LED is typically only ~2 volts. Going by this logic, the LED should have ...
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1answer
23 views

Adding luminous intensities (cd)

How do I calculate the Luminous Intensity (cd) of multiple LEDs spread across a 1.5m2 internally illuminated sign element? I have done this by treating it as a point source and adding each led ...
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137 views

Why does this LED not light up with 1.5V connected to it?

I'm a beginner in this hobby, and I'm confused as to why this circuit doesn't work when I connect it to a 1.5V battery. I tried it both directions, so I don't think the problem is polarity. Would this ...
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30 views

How to use reed switch to change operating modes?

I have a circuit of LEDs - say L1-L10. My requirements: No visible switch Illuminate the LEDs successively (only ever one at a time) every time the user passes a magnetic "wand" over the switch. (...
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1answer
31 views

Wiring 4+ 12v led ring switches from one 12v supply

I am new to electronics and general electronic circuits. I have 4+ led ring switches (from here: follow link) The website says that the rating of the switch contacts is 5A 250VAC with an ...
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29 views
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64 views

How best to lower LED garden light intensity

We have a house with an outdoor staircase lit by warm white LED strip lights. However, the lights are "too bright" and we want to lower the intensity of the LED lights. On another loop of the garden ...
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45 views

LED Board Driver Calculation [duplicate]

If there is a Board that has 100 LED diodes however using different Diodes that have Different specs (Maximum Reverse Voltage, Max Wattage, Maximum drive current etc.) similar to a Quantum Board LED ...
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1answer
60 views

Can I use USB to power a flashlight that runs on 3*AAA or 1*18650 battery? [closed]

I am thinking of buying this UV flashlight. It runs on either 1 18650 battery (4.2v) or 3 AAA batteries (4.5v). Since the flashlight can already take 4.5v, will it be safe to run on 5v USB? I found ...
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30 views

Part of LED strip only comes on pressing resistor

Hi I had recently purchased an LED strip for my car. Aliexpress Car Strip light However, after installation 3 of the lights on the strip stopped working. I noticed if I put enough pressure on the ...
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19 views

PWM drive of LED strip through long wire

I plan to drive a 12V/1-2A single color LED strip. The driver system will have MCU/MOSFETs like this https://www.makeuseof.com/tag/connect-led-light-strips-arduino/. The question is what MOSFET and ...
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18 views

Capacitor bank on source of mosfet

I want to drive a power IR-LED using a IRF2305 mosfet. In the gate mosfet I have a 5-10 Hz ...
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5answers
68 views

LED and Photodiode Data Acquirement System

So I am to develop a project this semester and wanted to be shed some light on certain topics. The goal of the project is the following: Detect a pendulum's period using an LED and a photodiode and it ...
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44 views

LED Brightness or Luminance is additive or not?

Let us say I have an LED whose brightness or luminance value is 50 Cd/m2. If I lit 10 same type of LEDs with same conditions of current and voltage then will the brightness of these 10 LEDs will add ...
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1answer
87 views

Using series of LM 78XX for power supply

I'm new in electronics. I want provide 9V (VVD9) and 5V (VCC) for my electronic board including power mosfets (IRF 3205), high power LED (14V-3.5A), micro-controller (at-mega16), and etc. I use this ...
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1answer
40 views

Converting Battery Operated Motion Sensor Light to AC Powered

I have converted many battery powered devices to AC adapter in the past. This time around I am using a Motion Sensor light which takes 4 C batteries and is used to light a closet. When I connect a ...