lights - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

Chip Amps Amplifiers based on integrated circuits

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 28th September 2012, 03:33 PM   #1
Kitax is offline Kitax  Latvia
diyAudio Member
 
Join Date: Sep 2012
Location: Riga
Default lights

i want to make music lights, and wanted to clear out a few things... i have got a lm386 chip, wich has a peak to peak output of 10 volts with 12 volt input. firstly i need to decrease the output voltage because the leds needs about 3 volts, but how low should the peak to peak voltage be for the LEDs to blink, but not burn?
also, how much input voltage does a regular mp3 or phone have on max volume?

and... Gain means how many times the signal gets amplified, right?
  Reply With Quote
Old 28th September 2012, 05:04 PM   #2
djoffe is offline djoffe  United States
diyAudio Member
 
Join Date: Oct 2008
Default LED part of your question

place two LEDs in parallel, but opposite polarity. Place a limiting resistor in series with those LEDs. If the LEDs were rated to take 10 mA peaks, you might choose a 1K resistor to be pretty safe.


www.akitika.com
  Reply With Quote
Old 28th September 2012, 05:28 PM   #3
Kitax is offline Kitax  Latvia
diyAudio Member
 
Join Date: Sep 2012
Location: Riga
ok... how do i calculate the output amperage? i guess the output watts devided by the output voltage, so max output would be the 0,5w/10v (output peak to peak)?

oh... how much rezistance does a diode have?
  Reply With Quote
Old 28th September 2012, 05:36 PM   #4
djoffe is offline djoffe  United States
diyAudio Member
 
Join Date: Oct 2008
assume the speaker goes from the amp output to ground (to eliminate confusion for bridge tied loads, etc). Let's say that the amp puts out at most +10 V or -10 V wrt ground.

Assume forward voltage on the LED of 1.5 Volts. Then the voltage across the resistor (maximum) would be 10-1.5=8.5 Volts. If you wanted this to correspond to 10 mA, you'd choose a resistor of 8.5/0.01=850 Ohms. The resistance of the LED is rather smaller than this , so could be neglected.

The power dissipation of the resistor, would in the worst case be 8.5 Volts times 10 mA, or 85 mW, so that's really not a problem.
  Reply With Quote
Old 28th September 2012, 06:34 PM   #5
diyAudio Member
 
Join Date: Feb 2011
use a trimpot to limit the input of lm386 and slowly raise it till the leds light up at the output.
  Reply With Quote
Old 28th September 2012, 06:53 PM   #6
johnr66 is offline johnr66  United States
diyAudio Member
 
Join Date: Mar 2009
It works pretty good with 9 volt supply and two white LEDs in series connected to the output pin (no coupling capacitor needed). Also add a limiting resistor of around 39 ohms. The LEDs are not on continuous, so it is okay to drive them harder. Since they are on for a half cycle, it looks more stobe like to me.

The bass is stronger in most music so the LEDs will flash to the beat. If too much HF signals are keying the LEDs, low pass the input.
  Reply With Quote
Old 28th September 2012, 08:16 PM   #7
Kitax is offline Kitax  Latvia
diyAudio Member
 
Join Date: Sep 2012
Location: Riga
well yea decoupling caps are ment to increase the quality if im right, so there is no point in using them with LEDs :P guess ill get a potentiometer, and set it up...

actually i wanted to know how much harder can i drive them...
  Reply With Quote
Old 28th September 2012, 11:48 PM   #8
Bare is offline Bare  Canada
diyAudio Member
 
Join Date: Dec 2001
Location: vancouver
Alll right! Tie Dyed TShirts and maybe even Disco Balls.
Frequency/music following colored lights.
What.. will they think of Next?
  Reply With Quote
Old 30th September 2012, 08:39 AM   #9
Kitax is offline Kitax  Latvia
diyAudio Member
 
Join Date: Sep 2012
Location: Riga
well dont forget a disco ball...
  Reply With Quote
Old 30th September 2012, 09:18 AM   #10
diyAudio Member
 
sofaspud's Avatar
 
Join Date: Nov 2005
Location: San Antonio
The output of an LM386 is at Vcc/2, so if you aren't careful your LEDs will be lit continuously (though they will change brightness with the signal). With LEDs in series, Vled1 + Vled2 must = >Vcc/2.
Quote:
actually i wanted to know how much harder can i drive them...
You've probably seen this before... Read the datasheet. If mA peak specifically.
Output voltage, output amperage, and diode resistance are mostly needless concerns here.
__________________
It is error only, and not truth, that shrinks from enquiry. - Thomas Paine
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Why are my lights dimming... carshateme Car Audio 27 30th October 2011 07:30 PM
neon lights Jordo Car Audio 1 21st November 2005 05:24 AM
very bright lights Aetzel Introductions 2 29th April 2002 01:09 PM


New To Site? Need Help?

All times are GMT. The time now is 07:57 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2