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 using a series resistor, or it can get more complicated, involving PWM and multiplexing.
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Turning on/off leds very fast. Will it do harm?
I am using an arduino board to controll a led strip. 3 transistor and 3 resistors are between the board and the leds. 1 for each color (RGB). I am using analogWrite to change the brightness.
But I ...
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Powering COB LED with "under-voltage" LED driver
I have LED Driver
Model: LD-361500-105MPF
Input: 90-260VAC 50/60Hz and
Output: 20-36VDC, 1500mA+/-5%.
I connected it to the LED COB Citizen 1212C4 which needs, according to datasheet (COB's ...
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Wind powered DC motor to LED
I am quite new, lets say green at this whole electrical game. Now that you know that, I have built a mini wind turbine that is powering a salvaged dc motor from a Kodak printer, and a green LED ...
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How many relays can I control arduino/raspi at the same time? [duplicate]
I'm thinking about a project using arduino or raspberry pi (I don't mind working with one or another). The thing is that in my project, I have to control at least.. 50 leds/relays and there will be ...
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OWI Robot Arm Circuit Diagram LED question
I was looking at the circuit diagram for the OWI Robot Arm Edge in the manual, and happened to notice the LED. To me, it looks like it has been drawn the wrong way around. But maybe I am wrong. Can ...
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Array switch circuit design
I am attempting to design an "array switch" where a user can toggle a switch and a different array of LED's are turned on based on multiple reference traces. The picture is my best attempt so far. I ...
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How to achieve constant current for LED when voltage is variable in MCU
I am using STM8S003F3 to drive 1 RGB LED. Link of RGB LED :- http://in.element14.com/broadcom-limited/asmb-mtb1-0a3a2/led-hb-rgb-0-09w-plcc-4/dp/2401106
To power the microcontroller and LED I am ...
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WS2812b LED strip power supply [duplicate]
I am currently trying to light up a staircase at my house. I bought two 5M reels of WS2812b 5V LED strips on AliExpress and some solderless connectors... I am planning on putting about 40cm on each ...
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Why transformerless power supply need a capacitor to decrease the current?
Assuming we have a 12 V load which needs 1 A current, when we connect this load to 60 Ah 12 V car battery it does not need to resistor and it will ony draw 1 A.
But on the other side, assuming we ...
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What lens/reflector when bouncing off ceiling [closed]
"I'd like to fill a room with ambient daylight by bouncing LED light off the ceiling."
EDIT: Poor wording, but by "fill", "ambient" and "daylight", I'm not considering the intensity, but just how to ...
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PIC's output pin not turning LED on
I've been trying to test my PIC just by turning a LED on, I verified that the PIC is energized and that the MCLR pin is HIGH.
The PIC I'm using is the PIC18F45K22, running at 3.3 volts.
The LED has ...
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Driving single 1W LED from 5V [closed]
I need to drive 2 high power LEDs (1 watt each) from a 5 volt supply. My current solution is to use a separate current source for each LED, each of which is made of a mosfet and bjt. This is only as ...
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Master switch to turn on and off independent lights
i am adding some led lighting to a dolls house where each room can be turned on and off independently but i would like a master switch which turns all lights off(simple) but should turn on all lights ...
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Power Supply for xl6001 12V Switching LED Driver
I have 2 nos 7W LED Modules, each of which are fed from a separate XL6001 based LED Driver. The DC power input to the drivers is from a 12V, 7.5AH SLA Battery. The LED driver takes 12V DC from the ...
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Constant voltage term in model of diode with internal resistance
Ideal diode equation is $$V(I)=\eta V_T \mathrm{log}(\frac{I}{I_s}+1)$$
Model:
simulate this circuit – Schematic created using CircuitLab
If the diode has an internal resistance \$r\$, a more ...
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How can I build a simple firefly (LED) circuit? [closed]
I'd like to I build a simple circuit with an LED to flash periodically like a firefly / lightning bug.
The timing part doesn't seem too difficult - just have to get the values right for the ...
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How to power led from arduino [duplicate]
I am new to electronics and ohms law is confusing.
When I power the led with analogWrite and give it only 3 volts do I have to still use a resistor?
When I power the led with 5 volts does it matter ...
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How to power two LEDs with a 1 Farad charged Super Capacitor as efficiently as possible?
I have came across a awesome super capacitor Flash LED Driver chip for cameras.
On page 10 of the LED driver datasheet, it says:
How long the LED current is regulated depends on the initial CAP
...
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LED switch on/off issue with wiring (transistors and grounding)
So my issue is that I am making a circuit that is able to control a light switch remotely. The items I am using are:
-Arduino Uno Rev 3
-TIP31c NPN Transistor
-PS2 wireless controller and dongle
-...
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High Frequency Blinking LED [closed]
I need to get an LED blinking at in the 1-5Khz range. I will use a photo detector to sense the blink rate to identify a drone.
The drone will be passing though a hoop about 1 foot from the sensor.
...
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multiplex numerous strips of WS2812
From what I understand, a strip of WS2812 LEDs use PWM to adjust the brightness (and thus current draw) for a given LED. If I attach several strips in parallel, each with its own data pin from my uC, ...
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Resistor for indicator LED on higher voltage (70V) DC
I'm driving an N-channel MOSFET on a 70Vdc supply (to power a pinball machine's solenoid), and I want to add an indicator LED to the circuit after the MOSFET, to see whether the MOSFET responds as ...
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PIR Sensor + LEDs with no additional Microcontroller [duplicate]
I'm thinking of building a project that would only include PIR sensors and LEDs.
Could I use a PIR sensor like this one, https://www.adafruit.com/products/189, to power 8 LEDs or would those 8 LEDs ...
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PWM Noise led driver
I'm working on an constant current led driver, in particular the TPS92512 from T.I.
There's audible noise when PWM dimming.
I think that the problem is on the inductor, but I don't know how to solve ...
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Can I use aluminium containers to transport ESD sensitive PCBs?
I want to transport PCBs mounted with LEDs which are ESD sensitive, in knocked down condition. Standard storage bins are not available in my specific size, hence was thinking to fabricate aluminium ...
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Is an led driver needed for simple circuit?
I have been working on circuits for a while, and when an LED has been needed I have always just put in the LED with a resistor. I have never really understood the need for an LED driver or what ...
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Projects that require 2 power supply voltages (Raspberry Pi)
I'm looking for some help building a circuit to supply a Raspberry Pi Zero, as well as a 1W RGB LED driven through a Picobuck driver. The Picobuck needs 12V and the Pi Zero just needs 5V (from a USB ...
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Multimeter fails to measure forward voltage
I have a MS8233D Multimeter and wanted to measure the forward voltage of some LEDs.
I connected the leads directly to the LED and used the Diode Testing Mode.
However the multimeter just displays Ol ...
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Amplifying an audio signal with an op amp
I'm trying to build a pretty basic color organ, but i ran into a problem and I can't seem to find the solution to my specific problem.
I built this circuit (using a 3.5mm jack connected to a phone or ...
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Modelling heat transfer from Power LED to metal bar
I'm playing around with workplace illumination and have developed a 20 V –> 38 V PWM'able constant current source to drive my power LEDs (max power about 64W). So far, so good. However, I've nearly ...
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How does a color cycling LED work? [duplicate]
I have a two prong led that when power is supplied to it, it twinkles and changes colors.
How does that actually work? It's too cheap in my opinion to have a micro controller in the diode and it ...
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Keep individual LED brightness steady when other LEDs are added or removed
I'd like to use several LEDs on a project, with brightness control (it's a scale model of a street with houses, with LEDs of different brightness in each house, which I've been working on with my son)....
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Do cool white LEDs emit UV light?
I have seen some internet electronic forums claming that low quality cool white LEDs emit more UV light than CFLs. Is there any truth in this claim?
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Why is a common LED failure mode to flicker astably or oscillate? [closed]
There are many cases of LED lights failing by beginning to flicker intermittently. I am not talking about the intentional duty-cycle modulation utilized in many driver circuits. I am referring to ...
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What is the UK standard E14 LED Candle bulb and holder for the US, is it E12?
I am making a table lamp and I'm going to try and mass produce it. I live in the UK but I will be selling in the US, does any one know the differences in voltage/wattage and light bulb holders? I am ...
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Can this circuit drive directly a led ( or even supply a BJT )
I've this PIR board:
https://www.mpja.com/download/31227sc.pdf
the chip output has already a 1KOhm resistor in series, so, since the one voltage of the chip is 3.3 V I guess I could connect directly ...
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how to calculate a total power consumption of LED
how can I calculate a total power consumption by given % of photons exit each LED and the Internal quantum efficiency and the Total light intensity? what kind of formula I should use?
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Reverse saturation currents of a LED?
What are the typical values of reverse saturation current of a LED? In particular is it possible to have a reverse saturation current of \$10^{-17} A-10^{-18} A\$ for a (red) LED?
For a silicon diode ...
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PC817 input features
I'm designing a new circuit and I need to know if PC817 allows AC voltage input around 230V.
I've tried with DC Voltage but never AC Voltage.
Does anyone know if it operates with AC input?
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Using multiple white LEDs to obtain a unique CCT
I need to swipe between two white shades from one to another color temperature, let's say from 2700K to 6000K. Can it be done by simply mixing the intensities of two LEDs of respectively 2700 and ...
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Why will my led not light up & why does my input voltage fluctuate when I add a wire?
This design is suppose to light up the LED When the sensor is under light, and turn off the LED when the sensor is covered.
I noticed two problems:
My LED won't light up.
When I measure the voltage ...
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DIY flashlight - USB plug [closed]
I want to do something like the first of the gadgets in this video:
https://www.youtube.com/watch?v=aEo_nJ3iUYI (0:07 - 1:00)
It's a flashlight connected to the micro USB port in my cell phone, but ...
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AC Light Bulb Fade Circuit - Resistors Getting Hot!
I'm building a circuit to slowly fade in (when switched on) and slowly fade out (when turned off) two LED bulbs.
The circuit works, but the two 100 Ohm resistors (see picture) are getting very hot (...
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led drivers and voltage overhead
More specifically this RF transmitter which has an incorporated led driver: http://www.mouser.com/ds/2/368/Si4012-35123.pdf
It specifies 4 levels of current on the LED output pin but nothing on ...
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control 3 status LEDs with 2 PCs
I'd like to control 3 status LEDs with two different PCs:
an OrangePI-PC, using the GPIO pins as power source (same pinout of a RPi2);
regular desktop PC, using the parallel port as power source.
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Help for a comparator circuit immune to noise with an LED indicator [duplicate]
I have the following circuit which uses an LM2903 comparator. But Im not sure if it is designed well enough, and not sure about the open collector output is used correct:
THIS CIRCUIT UPDATED AND ...
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LED's or OLED for creating specfic colors [closed]
I'm trying to create specific colors given the RGB values (please not that the RGB values go from (0-255) RGB LEDs use voltage to turn on and the voltage varies from color to color (The red LED in an ...
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Most efficient way to power a LED (with 2 modes) using CR2032?
It's new for me to actually ask a question here instead of only reading which I did appreciated a lot in college. I have a background in mechanical engineering and do have some (low level) experience ...
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LED Light Design Recommendation
I traced the below circuit from one of the WiFi based LED downlight available in the market. This circuit works at 17V (Regulated Supply) and takes 450mA max. current if fully bright. Now I am going ...
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Motorcycle flasher question
I wanted to add LED flashers to my motorcycle (I previously used 10W classical bulbs). After I installed both on the right side (front and rear) I noticed that they won't blink. They will turn on, dim ...
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