Tagged Questions
8
votes
2answers
187 views
How can I effectively reduce the voltage needed to activate a transistor?
I have built a circuit which basically connects the line out (audio output) of a music playing device to a set of LEDs (actually a huge strip of around 200 LEDs), so they flash in time with the music ...
3
votes
4answers
158 views
Creating a “Sharp” Turn on for LEDs
I'm building an analog audio VU meter just for fun (no microcontroller). I already have the basic functionality of the circuit working. However, I would like the LEDs that I'm using to have a sharp, ...
0
votes
2answers
88 views
LEDs in the audio path - linearity? [closed]
I'm repairing an ancient stereo multiplex decoder which has diodes in the signal path for mono/stereo switching.
For headroom reasons, I need plenty of Vf on these diodes, which are pulled up by a DC ...
4
votes
3answers
139 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 ...
4
votes
1answer
147 views
Does audio powered LED light with low tension require CE/FCC certificate?
I am building an LED light that plugs into the audio jack of a mobile device and is powered by the 3.5mm audio plug of the smartphone. The LED works at very low tension and with audio frequencies ...
5
votes
5answers
744 views
Simplest circuit that flashes and fades color LEDs synchronized to music?
This is about designing a circuit that can control multiple LEDs synchronized to music or sound, as simply as possible. I am looking for some conceptual ideas to start out with, not a complete circuit ...
2
votes
2answers
4k views
Driving LEDs from audio signal
I am making this very simple hobby circuit and I need help.
This utilizes the sound (variations) from the device through the jack to provide light (intensity) variations in the LEDs using TIP31.
...
1
vote
1answer
433 views
Solid State Relay two switch based on headphone audio output to control dc signal
Need to turn on an LED if there is any audio present out of the headphone jack of a cell phone (0.6v peak voltage). If there's no audio, need to turn off led. My plan is to hook up audio signal to the ...
2
votes
3answers
652 views
How do I make this LED flasher more sensitive?
I'm making a circuit which will change brightness level of an LED in tune with music. So far, this is producing some results, but I'm not very satisfied with it:
If it matters, the forward voltage ...
2
votes
2answers
939 views
Simple VU meter with Lm3915
I'm making a VU meter with an LM3915 and I would like to be able to plug my computers audio output into the LM3915 directly and get it to register. I've been searching the internet for a design but ...
2
votes
2answers
187 views
Why is the LED attached to pin 10 on and how can I get it to turn off
Here is the schematic that I'm working with: http://www.circuitsonline.net/schakelingen/59/audio/led-vu-meter.html
The LED attached to pin 10 is always on. Is there anyway I could get this so that ...
3
votes
2answers
952 views
How to make LED bar graphs to measure intensity
I'm working with this design.
I would like to make those LEDs into LED bar graphs that will show the intensity. For example, I want a song with a loud base to make the bar graph shoot up to the top. ...
1
vote
2answers
657 views
Can I replace MC33204P with one of these other op amps?
I'm working to make this schematic
and I was wondering if it is possible to swap out the MC33204p with either LM348N or LM339AN. And if you could let me know why swapping them would still work I'd be ...
3
votes
3answers
461 views
Analog, discrete component fade-in
This is probably a very easy question, but I've been trying for several weeks now to create a simple circuit that "fades in" some LEDs using only discrete components like resistors, capacitors, ...
