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.
6
votes
2answers
119 views
Ring oscillator not oscillating
Inspired by this blog post, I decided to put together a simple ring oscillator that transitions through 3 different LEDs. My schematic is almost identical the one in the blog post except that I used ...
2
votes
3answers
129 views
PWM duty cycle vs candelas for LEDs
What is the functional relation between PWM duty cycle for LED and its luminous intensity (candelas)? Linear or not?
7
votes
1answer
329 views
Why does my resistor get warm?
I am currently using 150R series resistors to limit the current to each segment in a 7 segment display. I picked 150R because all the online "led resistor calculators" suggest this value. The power ...
6
votes
1answer
139 views
Simon Says without Microcontroller
I'd like to create the classic game of Simon Says utilising nothing but logic circuits, LEDs and ICs, no Microcontrollers like the Arduino.
I would like to use 4 LEDs and 4 Tactile Switches for this ...
1
vote
1answer
115 views
How to design a load
Requirements:
I need to design a load that will be powered with 1-4 supplies at any given time. The design requirements are merely that if 1 or more supplies are 'on', there needs to be at least 1 Amp ...
5
votes
1answer
87 views
Switching MOSFET from Raspberry Pi GPIO
I'm trying to drive a STP16FN06 from a Raspberry Pi GPIO pin but I'm a bit lost.
The schema below represent (I think) how it is currently wired, on the left the RPi pin + ground and on the right a 5V ...
4
votes
1answer
120 views
Driving three high power RGB LEDs with PWM, from a 9v battery
I'm building some LED juggling balls. I'm planning to power an Arduino with two AA batteries, and power the LEDs with a 9V battery.
I want to drive three of these 3W RGB LEDS in parallel, with PWM. ...
4
votes
2answers
229 views
“Ideal” Solid State Switches?
I want an LED to turn off when the input voltage falls below a certain point, e.g., 3.3V. Originally, I was going to use a basic 2N2222 or 2N4401 transistor, however, because they act as "amplifiers" ...
0
votes
1answer
78 views
Trigger a relay with a very low DC voltage
I want to light up a couple of LEDs using a relay to trigger this event. I have a very low DC voltage, about 0.15mV to 0.20mV and I want to somehow take this voltage to a relay, that will be also ...
1
vote
3answers
121 views
How to keep led in “ON” state using 555 IC?
I have made dark detector using this following circuit diagram:
Whenever the LDR is closed with finger,the LED would glow. Now all I want is to keep that LED in ON state for a while or ...
10
votes
3answers
383 views
What is the difference in this specific breadboard wiring?
As an absolute layperson in electronics I just found out that an LED only lights up when connected like in figure 1 but not when connected like in figure 2. And I just don't get why?
I know an LED is ...
5
votes
2answers
81 views
Arduino + Android : Communicate with a JY-MCU Module
I am trying to turn ON and OFF a LED with my Android Device through a Bluetooth module (JY-MCU V1.05), I can connect to the module with the key "1234", but when I send a command to the module through ...
1
vote
0answers
54 views
Relay based auto key circuit
simulate this circuit – Schematic created using CircuitLab
Hello all,
I am trying to make simple circuit that will basically pass a signal from a signal generator to another circuit that ...
8
votes
2answers
141 views
What are the tradeoffs for the various options coupling a LED to an optical fiber?
I'm trying to couple a white LED to a fiber bundle that's comprised of several 30 uM silica fibers. The bundle outer diameter is on the order of .5 mm. The NA of the fiber is .87 and the whole ...
1
vote
1answer
78 views
Microcontroller Newbe here. LED color pattern controller for arcade machine [closed]
I am building an arcade machine and I want to make a cool led light display for the marquee.
You can see pictures of what I'm talking about here.
I want to light up each one of those holes with ...
