Questions tagged [brightness]

Brightness is an attribute of visual perception

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7 segment LED displays

I notice the surface area of the decimal point in my 7 segment displays is only 1/4 of the ABCDEFG segments. Should I reduce the drive current accordingly, to achieve matched brightness? Can't find ...
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Efficiency of green High Power LED compared to efficient white

Whenever I see color High Power LEDs (for example green 3W on Star) I see disappointing efficiencies: For 520 nm the theoretical efficiency is 683 lm/W * 0.88 (green) = 601 lm/W. But most are ...
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1 answer
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How to adjust both brightness and contrast of a TFT LCD display

I am developing an HMI using the display "S039QWQ01HS" and I have the requirement to provide control to adjust the brightness and contrast of it. For the brightness control, I have already ...
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How to measure intensity (lumen) of a light source?

Let's say I have an x800 cree LED (which was supposed to be 4000lumen) and a cheap lux-meter (thinking of buying one like this). My question is, which is the physical setup to measure the true ...
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Globe brightness in series circuit

So in a simple DC series circuit, why do some globes shine more brightly than others? And which ones are the brightest? Obviously each consumes a certain amount of voltage but I don't think the ...
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2 votes
2 answers
589 views

How can I regulate brightness of a LED strip with a potentiometer

I have a 12V, 5m long LED strip and an adapter (12V 1A). I want to control the brightness of the LED strip with a potentiometer, I found a simple circuit that involves only a pot and IRFZ44N ...
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increase the maximum brightness for a laptop replacement screen [closed]

I would like to increment the maximum brightness for a laptop replacement screen such as this one How difficult that could be? I haven't bought the screen yet so any hint about the type / model and ...
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How to specify UV high brightness LEDs?

I'm trying to find high brightness UV LEDs appropriate for this project: https://www.instructables.com/id/UV-LED-Exposure-Box/ which includes: "The most critical parts of this project are the UV ...
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1 answer
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How do I use the Z-input on my oscilloscope (full range of contrast / brightness)?

I guess all scopes are a little different and don't provide any adjustment knobs for the Z-axis input. Mine is a Protek 6502A and it's Z-axis spec says Z Axis Modulation: Sensitivity: 5V P-P (...
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Make my battery level indicator dimmable

I wired up this battery level indicator using a 9V battery (power supply is for ease of changing voltage.) It works well with only D1 lit at 6 volts up to all five LEDs at 9 volts. My problem is ...
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How can I find the PPF of an LED?

I want to built a LED panel with a high photon flux, and photon flux density, (the LEDs have a specific wavelength) but when I start to search wich LEDs I am going to buy, all the sellers just give me:...
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1 answer
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How can I make a 16x16 led pannel without losing the brightness intensity of each single led?

So, this is my first question here in this forum and I don't know if I'm doing this right. Then in fisrt place, I'd like to apologize myself if I'm doing something wrong or if my english is a little ...
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LED 10mm 8400mcd loses brightness using battery A23 12V

I have a problem: I'm supposed to produce bicycle lamps. The LEDs should be white, and super bright as possible, use batteries A23 12V, with a resistor (I'm using 2 MOhms,) and last for around 48 ...
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Brightness of LEDs

I am currently in the design phase of building a digital clock (about 2ft by 4ft in size.) It should be fairly visible from a considerable distance (about 100 ft) and visible during the day. I am ...
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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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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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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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TFT RGB LCD construction and

I am trying to understand the construction of an RGB TFT LCD that has brightness control in it. I could not understand how does the TFT color LCD pixels glow? Does each of the pixel has its own light ...
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Effect of changing PWM frequency of a light source on perceived brightness

First and foremost, I'm not entirely sure if this is the proper place to post this question, so I apologize if there's a better section for this. I am looking to determine the effect of changing the ...
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Microbit - Control an LED that is powered externally

I am trying to make a motion activated light with my Microbit. I have a 1W superbright LED and its clear the Microbit won't supply the current needed for this LED. So I'm using a 5V USB micro-B with a ...
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5 votes
6 answers
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Simple LED fade circuit

I've been looking for a simple LED fade in/fade out circuit when power is turned on/off for a 12 V LED. I have tried the following circuits but the problem is that I can't reach the full brightness of ...
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Using latching Hall sensor to toggle a LED - brightness issue

I'm using a U18 latching Hall sensor (datasheet) to toggle a LED. I'm driving it off a 6V L1016 battery. My issue is that the LED is very dim. My understanding is that the U18 limits the output ...
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Keeping your LED cool with PWM

SO I need to use some 1W and 3W leds for the brightnes, but my application will not allow the start heat sink. I have come across a few articles talking about using PWM to drive LEDs Does pulsing an ...
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2 answers
160 views

Undesirable ramping in LED intensity

First time posting on this, so apologies if I mess anything up. I'm having an issue with my circuit that I'm having difficulty figuring out. I am using a TIP120 transistor to turn an LED on/off. The ...
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3 answers
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How to compare brightness of different color LEDs (not RGB)?

I wonder - let's assume one would build some user interface using green, yellow and red or just any other available colored LED (not RGB LED) - what would be the proper (aka best) way to compare the ...
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How significant is 16bit in 16bit PWM resolution? [closed]

Is there any significance other than the granularity of duty cycle levels?. I'm working on an led driver where the light output levels should be very smooth while dimming. There will be 254 levels of ...
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LED perceptive intensity by Color

BACKGROUND I have a panel with light indicators (LED) in RED,GREEN and YELLOW. Since the eye have different sensitivity to different colors, some colors must be brighter than others to be percepted as ...
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The brightness of light bulbs in this circuit

What will happen to the brightness of bulb A and bulb B in the circuit shown in the figure when we move the wiper of the rheostat from point x to point y? When the wiper moves from point x to point y ...
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The brightness of the bulb

I came across this question in my book, it says: This circuit has three identical bulbs, what will happen to the brightness of the bulb (B), when we close the key (S). (Consider that the internal ...
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3 answers
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How can I calculate the current through an LED? [duplicate]

I am trying to find out if increasing current increases the brightness of an LED. I'm pretty sure this is the case now that I have looked into semiconductor band theory physics and p-n junctions. ...
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3 answers
823 views

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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3 answers
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How Is Intensity of Blue Light Measured?

As a hobby project and to help solve issues getting up early in the morning (specially given that it's winter and the sun isn't up until long after I am) I'm trying to find a bright blue light that I ...
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3 answers
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How to build a light sensor for PWM dimmed light (for comparison against CC dimmed light)?

I am working on a project in which I need to find a PWM duty cycle to dim an LED to the same brightness level as an LED being dimmed with CCR. Initially, I was considering using a camera for this: I ...
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1 answer
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How to create an output for LED brightness control using PWM in PIC

A PIC is multiplexing multiple common anode 7-segment displays. An LED driver is being used so PIC does not have to source/sink a lot of current. To help with multiplexing, each 7-segment display ...
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Matching LED brightness from different supply voltages

In an earlier project, I used an LED to indicate power (this 12V model). The PSU delivered +15V. I adjusted brightness with a 5k series resistor. According to the datasheet, this particular white LED ...
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How can I decrease the brightness of these BA-15 LED bulbs

I'm looking at these LED replacement bulbs for the interior of my sweet conversion van. I'm looking for a more efficient alternative to the BA15 bulbs that are in there already. These bulbs appear to ...
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1 answer
2k views

10x10 RGB LED Matrix Multiplexing with Shift registers Bit Angle Modulation

I've build a 10x10 RGB LED Matrix. The LEDs are connected in rows and columns. That's 40 pins (30 for RGB, 10 for GND). I got myself five 74CH595 ICs and soldered everything together. I also added a ...
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7 votes
3 answers
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Circuit to create X levels of brightness for a LED

If I'm here today, it's because I need some help for something that is, I think, easy for you. I am quite a newbie in EE but I am trying to improve myself :). Here is the thing, I'll try to be as ...
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2 votes
4 answers
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Dimmer effect (fade) on 12v LED using transistor and Arduino

I am working on a project on which I want to control the brightness of a 12v LED using a transistor and an Arduino board. So far I have used the 2N3906 resistor connecting the collector to the 12v ...
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3 answers
365 views

Adding a dimming knob to a step up power supply

I am a ME student with little EE knowledge, and I currently have a setup which includes a 12V SLA battery, a 100W LED chip and a constant-current constant-voltage step up converter. The board can be ...
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3 votes
2 answers
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Measuring display brightness decay

Our device is specified to have a display brightness of 500 cd/m² and it must not decay to less than 50% brightness in 50,000 hours. Now, I can't wait for 5.7 years for that test to finish. I guess ...
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1 vote
1 answer
668 views

If LED's have different bin codes, how can I know what I am buying?

I will start by confessing I am a hobbyiest engineer (ie: still in school) and thus am open to allegations my concerns are not terribly important. However, I have this: I was looking at page three ...
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-2 votes
2 answers
100 views

How bright are the dimmest LEDs and what's their typical usage? [closed]

High power extremely bright LEDs are more and more popular in various lighting applications. What about extremely dim low power LEDs? How bright are those and how are they typically used?
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Keep brightness high whilst multiplexing [SOLVED]

I have searched a little but I'm a noob to electronics so it was hard for me to understand. So here is my problem. I have made a little 3 x 3 led matrix to test. When powering 1 led it was fine, but ...
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shift register RGB led brightness

I'm currently using 74HC595 shift register to light leds. Recently I decided to start using RGB leds instead of simple 1-color leds. Which means that I now have to ...
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1 answer
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Does HDMI manage backlight?

I need to manage backlight on a 7 inches touch screen from Chalkboard Electronics that has a HDMI connector and a power jack only. I only need to power backlighting on and off. Can it be done through ...
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6 votes
2 answers
2k views

LED blinking with capacitor and schottky diode?

I saw one circuit which connected one 100uF capacitor and one schottky diode as mentioned in the below circuit diagram. It has a negative logic rectangular pulse at cathode of the LED, which is ...
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3 votes
1 answer
19k views

How to add lumens

I have n bulbs of luminosity k in fixture a. How many bulbs of luminosity l do I need in fixture b for the brightness of a to match the brightness of b? Specifically, I'm wondering how many standard ...
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4 votes
1 answer
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How does area and intensity relate to perceptive brigthness of a light source?

I want to design tail-lights for onboard use in vehicles (mostly bicycles), but I wonder how should I configure the system so as to get the best visual perception from a distance. Each lighting ...
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3 votes
3 answers
9k views

Is there a simple way to diffuse the light of a "super bright" 5mm LED?

I want to put yellow leds inside the turning-signal cases used in motorcycles. The problem is: since the case is not deep enough, when I look from far I can only see the focused, pin shaped LED ...
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