Tagged Questions

3
votes
1answer
86 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 ...
2
votes
1answer
89 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 ...
0
votes
0answers
53 views

LED display has noise

I am developing a LED display driver. It uses a PIC18F452 microcontroller and a 74hc245 IC. It uses the SPI protocol to send signals to the LED display. When there are small number of LEDs switched ...
4
votes
2answers
123 views

buck converter for high current LED

My first question here: I want to make a simple adjustable current supply for some LEDs I have (approx 3 V and up to 3 amps). I've decided against just using a single FET to control current as it ...
7
votes
2answers
270 views

How do I know where to place resistors on my circuit?

Some of the books I have state that power comes from the negative terminal on the power supply.If that is the case, the circuit starts from the negative right? Say I have a simple circuit with a 6v ...
4
votes
2answers
67 views

Determining a suitable Power Supply for a Light

I have an old multi-coloured LED lighting system, but sadly I have lost the power adapter to it and there are absolutely no markings (exterior or interior) whatsoever, so I am trying to figure out the ...
1
vote
1answer
396 views

How to drive high power LED and Arduino by the same power source?

I am building a plant light consisted of 24 high power LEDs (Cree ML-E) and an Arduino Uno. I would like to power the LEDs and the Arduino by the same power source. Since creating circuits for dealing ...
1
vote
1answer
476 views

A basic buck converter circuit to power 3W LEDs from PC power supply?

I'm just finishing up my first electronics course (edx.org), and I want to build some LED grow lights for starting seedlings in the winter. I have high power LEDs, like this one here, and I have a PC ...
0
votes
1answer
520 views

How to power an arduino controlled string of RGB LED's from separate power source

I'm new to electronics and working on a hobby project that will have an arduino board running 5 separate strings of RGB LED's. I'll be using a PWM chip (TLC 5940) so I can independently control tho ...
1
vote
2answers
298 views

High power LED's and a computer Power Supply?

Is it possible to dynamically power a multitude of approximately 1W LED lights via a computer/computer power supply. Ideally I would like to be able to control these LED's via a USB interface or ...
3
votes
1answer
142 views

Wiring Considerations for numerous LED's

I'm working on a hobby project where I'm going to need to wire up 40-80 (not sure exactly how many yet) LED's of various colors. Only 10-20 of them are going to be on at a time. This is going to be a ...
7
votes
3answers
634 views

Why is LED lighting up despite Supply voltage < Forward voltage

I have an LED which has specified Typical forward voltage of 3.5V and Maximum forward voltage 3.9V. I applied 3.3V across it with a 300 Ohm resistor in series. Why did it light up? I am wondering if ...
2
votes
2answers
183 views

CREE LED and Driver

I have this LED. And I have this driver. I'm trying to use it to drive the LED however when I hooked up the one LED to the driver it started smoking. I measured a voltage of 48V while it was working ...
3
votes
3answers
276 views

Getting ~600W of power to 2048 LEDs

Despite my Computer Systems Engineering degree, I haven't played with electronics for over a decade, and I'd like to get back into it. I have a project idea, and I think I've got all the design leg ...
1
vote
3answers
267 views

Powering 3 LEDs

I have 3 LEDs which I assume are white (they look white, in a blue glass/plastic). I need to power them, but Im a bit rusty with my electrical knowledge. I have the following power supplies (all ...
1
vote
2answers
1k views

Using Multiple Power Supplies with RGB Leds and Arduino

I'm trying to control 3x 5m RGB LED strips using an Arduino Mega's PWM pins. Building off ladyada's tutorial: http://www.ladyada.net/products/rgbledstrip/. I created a 3x3 bank of N-channel mosfets, ...
1
vote
2answers
219 views

Hooking up LEDs to a drum set - Fire Hazard to plug into a wall?

I have a friend that wants to hook my drum set's double-bass pedal so that everytime I press it down, it'll light up these kind of LEDs around the 22" diameter bass drum head. Each pedal would be ...
2
votes
2answers
2k views

Add on/off indicator LED to circuit

I'm working on my first small electronics project; building a small LM317 based power supply. I've built the circuit as shown in the data sheet (black part of the circuit diagram below) on a ...
2
votes
2answers
712 views

Arduino and LEDs Power Supply Question

First, thank you to anyone taking time out of their day to read this and answer. Resources like this are incredible for amateurs like myself. My question is based around power supplies, Arduinos ...
2
votes
3answers
517 views

How to non-destructively test unknown LED strip?

I have a tiny LED strip that I took out of a smashed LCD in my Digital camera. I remember lighting up the strip in the past but can't remember how. I have been trying now with my bench supply to ...
7
votes
3answers
619 views

Need help with eliminating LED-generated noise

I am very new to electronics, to electronics.SE.com and this is my very first project, so bear with me if my question misses some key-information (in such case, just leave a comment and I will try to ...
3
votes
2answers
181 views

cable jacket melts

I am new to hardware. My breadboard just arrived and I am trying to light up my LED. I used computer power supply for power (red wire for + black for -) and used strands of LAN cable for connect LED ...
3
votes
3answers
485 views

How do I build a cheap/efficient mains adapter for some LED lighting?

I've been considering building some LED lights to replace the mains-supplied lights in my house (as a more efficient alternative). For it to be worthwhile though I'd need to build an efficient UK ...