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.
0
votes
1answer
23 views
TLC 5952 Blank pin control
Can BLANK pin of TLC5952 device be permanently connected to ground or does it need to be toggled (once at the startup or each cycle...)?
5
votes
2answers
112 views
Will LEDs in opposing directions be damaged?
I was trying to build a simple RC circuit that causes an LED to fade in and out. However, I have electrolytic capacitors, which means that they have polarity.
If I connect a circuit as follows , is ...
3
votes
1answer
105 views
Safely extract power from USB
I am upgrading the lighting in a model with simple circuit which has 17 LEDs (approximately) plus one or two 555 timers. Presently, everything is powered by 3 AAA batteries. It drains between 150 and ...
0
votes
1answer
90 views
What voltage is put across the Tx+, Tx-, Rx+, and Rx- lines over ethernet?
I'm trying to figure out how to wire up an LED, probably controlled by a FET, for an activity indicator for ethernet. I'm not trying to make one that supports official error codes or anything, but ...
3
votes
1answer
60 views
Reducing LED PWM Noise: Which is the best option?
Driving an LED with a microcontroller should be easy. But when looking into noise, things can get complex...
As an instantaneous voltage indicator used in a variable power supply (which will be used ...
4
votes
3answers
107 views
How do I amplify a dc voltage that is too weak to trigger the base in a transistor?
I'm trying to take the voltage output from a 3.5mm audio jack and have it light up an LED according to it's voltage. I was going to attach the left audio cable to the base of a 2222n transistor which ...
1
vote
1answer
39 views
How to plug 2 5m RGB LED light strips together?
I got two 5 meters RGB LED light strips and would like to connect them together, controlling them as a single strip.
Each strip power is 72 W, the input voltage is 12V, it has 300 5050 SMD LED ...
4
votes
1answer
52 views
How to calibrate an optical particle sensor (Mie scattering)
I have a very simple sensor that basically emits infrared light (1 micron wavelength in the infrared range). The light scatters off particles whose diameter is of the same order of magnitude as the ...
1
vote
1answer
53 views
Multiplexing with or without transistors
I'm doing something in where I need to multiplex 6 7-segment displays. About doing it, I found things like this:
And things in where the same thing is done without the transistors, just by ...
1
vote
0answers
62 views
Alarm Clock 7 Segment LED display
I recently got an alarm clock from goodwill and took it apart and am probably going to use the display for some tests. Here is a picture of the front of the display:
The text on the left is ...
2
votes
1answer
59 views
Need help setting up 7X6 Piranha LED Matrix with Arduino
I need help correctly getting my parts list for a 7X6 matrix that will be part of a electronic outdoor scoreboard.
Here is my parts list so far but I am stump whether the arduino is powerful enough ...
0
votes
2answers
65 views
How to drive 32-by-32 (or more) LED matrix?
I have a matrix of 32-by-32 LEDs that I need to control using a driver. The largest driver that I found was a 16-by-16 driver by Linear Technology, and there is no driver that goes higher than ...
5
votes
1answer
101 views
Circuit that switches one led ore all three
For an analog photo enlarger (yep, that vintage stuff) I own, I would like to build my own lightsource. For the prototype I found 3 colored super bright led panels they use 12V
The problem is that ...
-3
votes
1answer
102 views
I want to build a portable railgun and I'm a complete rookie [closed]
I'd like to enter the world of electronic hobbies by making a railgun, and so far I know that I understand the basics of the device and that I need high amounts of direct current.
However, I am ...
1
vote
2answers
82 views
Finding wavelength from infrared LED in a photodiode sensor
w
I have a dust sensor that emits LED light, scatters the light of the material and records the light intensity via a photodiode. I know the LED will emit light in the infrared range. I want to know ...
-2
votes
0answers
45 views
power led to monitor plugged device [closed]
I am trying to create an experimental circuit to handle groups of HDDs (SATA) for multiple PCs. (e.g. I can swhich which PC control which group without having to move cables).
The thing is, I would ...
2
votes
1answer
93 views
Multiplexing large LED matrix
I have a project which involves building a 64 x 48 (3072) LED matrix driven by a Raspberry PI computer. I am a first-year computer engineering student so I am still inexperienced with shift registers ...
-5
votes
1answer
69 views
How do I make several LEDs flash and fade in sequence? [closed]
I'm thinking about making a pin or button containing LEDs that will repeatedly pulse on and slowly fade out. This is similar to the loading icon popular with Apple devices or an indication LED in a ...
3
votes
1answer
50 views
calculating resistance for LED strips to use as parking lamps and turn signals
I'm installing LED strips in my car's tail lamps to convert it from conventional bulbs to LEDs. I have a understanding of what I'm doing but not the complete knowledge to make the circuit work ...
2
votes
1answer
56 views
Creating an LED array light box
I'm wanting to make a light box of sorts from LEDs and wanted to run it by you to confirm I have the right idea...
I have ordered 500 super bright LEDs off eBay and want to wire loads of them ...
1
vote
3answers
134 views
How to light an LED when a voltage hits a certain point
Lets say I need an LED to indicate when a DC voltage reaches 5 volts or more. I don't want the LED to be dim when it is at 4.5 or anything. I just want it to be full bright at 5, 0 bright at anything ...
0
votes
0answers
48 views
Multiplex data and LED pin
I'm looking at performing a chip conversion for the Sparkfun LED RingCoder. The sample code provided with the product works well on an Arduino UNO, but it uses a pin for each I/O - 5 pins for the ...
3
votes
2answers
68 views
Controlling LED with 300mV AC signal
I would like to control an LED with audio signal, but the problem is, that output signal is only 150mVpp (with 150mVpp positive offset). In my understanding, it needs to be higher than 0.6V to get the ...
3
votes
2answers
72 views
How to use the same switch to control LED and vary resistance?
I am struck with a simple board design problem.
The requirements are : I have a 4 position slide switch according to the position of the slide switch, I should turn on different colored LEDs and also ...
-2
votes
1answer
108 views
led Wire diagram [closed]
We have connected 2 led parallel and then series with another 2 led parallel combinaton another channel same as it is and then connect both the channel parallel.
We want to calculate the value of ...
0
votes
0answers
71 views
lm555 circuit doesn't work
Why doesn't this simple circuit work?
\$R_1 = 15k\Omega\$
\$R_2= 15k\Omega\$
\$C_1= 1000\mu F ; 6.3V\$
\$v= 9V\$
It should have a cycle time of 30 seconds.
I placed a volt meter on a LED that was ...
1
vote
1answer
40 views
Does a photo-coupled SSR need a series resistor for the internal LED?
I am trying to control an LCA710 SSR with an Arduino digital output. The data sheet says the control inputs are "CMOS and TTL compatible". It also has a schematic of the internals of the chip, showing ...
-8
votes
0answers
54 views
Air Conditioning Leakage Detector [closed]
This is John Smith. We are all seen that many people give different ideas and suggestions on same concepts. Some of them may be almost similar with others opinions and some of them may be different ...
1
vote
2answers
63 views
how many resistance do i need to safe the LED of PC814?
if i have a input of 5v (arduino HIGH) on the LED of a PC814, how is the value of the resistance that i must use before that, so i don't burn the led?
...
4
votes
2answers
98 views
Why does the led turn dim gradually and then turn off when attached to a capacitor in series?
I connected an LED in series with the capacitor (any type of capacitor. I used one of 10 μF) and connected them with the 9V DC battery. I connected the positive pin of the capacitor directly to the ...
2
votes
1answer
47 views
Is NRTL approval required for the sub components I purchase and assemble into a final product in order to sell the product in USA?
I manufacture a lighting product made up of components I purchase and then assemble into a housing and heat sinks that my company manufactures. The components I assemble include an electrical driver/ ...
0
votes
2answers
59 views
Choosing leds for batteries power
Can I use 3V (2*AA or 2*C batteries in series) as power for 10/20 leds connected in parallel?
LED specs:
Diameter: 3mm / 0.1"
Emitting color: Red/Green/Blue/White/Yellow
Material: GaP
Forward ...
1
vote
2answers
62 views
Arduino multiplexing help needed.
Is it possible to use an 8 output demux to switch between seven 16 output demux's in the case that I want to control several LED's with an arduino uno? Is there a better way to do this?
4
votes
3answers
231 views
How long would a 150 Farad Capacitor light up an LED
I have a bright white LED from a flashlight. Aproximatley How long will it light up with a 150 farad 2.5 volt capacitor. Do I need a resistor? And if so how many Ω? The capacitor is a maxwell 150 ...
1
vote
1answer
92 views
how to control constant current led driver output with pwm?
i want to control brightness of led series with constant current power supply.
but when i connect the power supply output to pwm controller and led series, i cant control the brightness because power ...
5
votes
2answers
86 views
Similar LED, higher voltage drop, less bright
I was measuring voltages in my circuit, and noticed something strange.
I have an array of 8 LEDs. Each of them is in series with a 220 Ohms resistor. The circuit has a 5v source.
simulate this ...
3
votes
1answer
133 views
Higher current LED driver for persistence of vision display
Project needs
We need an inexpensive LED driver IC that:
Can source or sink at least 15mA/LED
Has an SPI-like interface (not I2C)
Has a separate latch pin
Has at least 256 grayscale intensities
...
1
vote
3answers
77 views
Higher resistance resistor in place of higher wattage?
Engineering newbie here. I'm fairly sure I already know the answer to the question, but I figure I'll ask anyway.
I've got an LED lying around, that according to an LED calculator requires a 80R 1/2w ...
-4
votes
0answers
60 views
Connecting Samsung LED Digital Audio Out to Creative 4.1 speakers [closed]
I have currently a Samsung - UA40D5900VR LED TV which i need to connect my Creative Cambridge 4.1 computer speaker
My TV has only Digital Audio OUT (optical) whereas my speaker has 3.5 mm male ...
5
votes
1answer
173 views
How does this LED setup work?
I noticed this LED setup in a datasheet for the Kingbright SA40-19EWA. Instead of the leds being in a simple series or parallel setup, each segment of the display has four sets of two leds in ...
2
votes
0answers
130 views
Make an LED Ring Light Up Smoothly?
I am working on a project that would look really cool if I was able to put a ring of LEDs (kind of like the one on the TRON Identity Discs) light up smoothly in a circle, rather than have sections of ...
0
votes
1answer
50 views
Shifting between PWM options
I'm using a Freescale MC9S08DZ60 microcontroller, and Ive written the code for applying PWM on a specific pin.'This is an attempt for Breathing Effect of LED, a question i had already asked - LED ...
1
vote
1answer
58 views
What value resistors should I use for this LED?
I'm trying to figure out the actual value resistance I need for the RGB LED I bought from here: http://www.adafruit.com/products/314#Description
According to most of the online calculators, for the ...
0
votes
0answers
80 views
Source and sink driver ICs for LED matrix display
I am building a led matrix display (16 cols x 8 rows) using 1/16 duty cycle for multiplexing the display. As per my understanding LED requires 20 ma forward current when drive directly and it will ...
2
votes
2answers
106 views
How can I control 8 LEDs with a timing delay with only one microcontroller (PIC12) written in Assembly?
I can have 5 I/O pins enabled. I'm just confused on how to control them individually.
2
votes
2answers
113 views
Energy-efficient LED driver circuit
I want to light a normal LED for as long as possible on two AA or AAA batteries. It does not have to blink or so, just stay on. The LED doesn't have to light at the max, as long as it's visible from ...
1
vote
1answer
66 views
How to power a 12v outdoor project with microprocessor?
Forgive me if this is a really basic question, but I'm still at the "consideration" stage of a basic LED project, thinking about lighting up one of those flexible LED strips from a microcontroller ...
8
votes
2answers
111 views
Why does my 555 stop oscillating under load?
I've got a 555-timer circuit. When I examine the output-pin on an oscilloscope, I get a nice square wave.
I want to turn an LED on and off, so I've attached an LED and resistor to the output pin ...
0
votes
4answers
120 views
How can I make LED's light up equally?
I have built a Binary to Unary (kind of) circuit on my breadboard.
It looks like this:
simulate this circuit – Schematic created using CircuitLab
There are three switches that ...
1
vote
1answer
107 views
Getting LEDs brighter without drawing much more current
I am developing a bike light that runs off of a 3.7V Li-Ion battery. I am currently running 3*10mm Ultra Bright White LEDs (~25,000mcd each). They each draw 20mA.
I am relatively happy with the ratio ...
