Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

pulsing leds off with beat

Status
Not open for further replies.

aircm

New Member
Hi all, i wish to create a simple circuit for led pulsing, i would like the leds to stay on when there is no beat or music. when the music starts i want them to pulse off with the beat. I have seen a circuit that uses a tip31 but this works in reverse. I will make 2 circuits left and right channels.
 

Attachments

  • Building-the-circuit.GIF
    Building-the-circuit.GIF
    7.7 KB · Views: 333
Last edited:
Hi all, i wish to create a simple circuit for led pulsing, i would like the leds to stay on when there is no beat or music. when the music starts i want them to pulse off with the beat. I have seen a circuit that uses a tip31 but this works in reverse. I will make 2 circuits left and right channels.

hi and welcome,
Post that circuit and we can suggest how to modify it, so that it does it the way you want.
 
Perhaps try adding a resistor (maybe 10k) between the transistor base and +12V, and a capacitor (maybe 10u) between the transistor base and the audio in. You should also connect a resistor in series with the string of LEDs to limit the current to whatever they require.

The resistor will try to keep the transistor turned on, while the capacitor will turn it off when the audio level is sufficient.
 
The circuit was an Instructable and was designed by somebody who knows nothing about electronics.
It has nothing to limit the base current from the music source to the base of the transistor so the music source and base-emitter of the transistor will probably be destroyed.
There is nothing to limit the collector current so if 4 red LEDs are used then they would also be destroyed.

Since blue LEDs are 3.2V to 3.6V then 4 of them will not work in series with a 12V supply.

If you use a resistor to bias the transistor on, then music will not turn it off because music is AC, not DC. You need a rectifier and a filter capacitor to turn another transistor on which turns this transistor off during a beat.
 
12v leds

I am just using this diagram as a guide, the leds i am using are 12v and 1 led only for each channel.
 
Do you understand that the base of the transistor can be destroyed by an audio amplifier and the amplifier output can be destroyed by trying to drive a very high current into the base of the transistor without having proper current-limiting parts?
 
leds

Ok i understand that is not the correct way to do it, then what is or is there a circuit i should be looking at.
 
The "beat" in western music is usually bass frequencies. Then you need a small amplifier with a lowpass filter.

The output of this amplifier is probably AC but a transistor to drive an LED needs a DC input because the negative voltages of AC will destroy it. So the lowpass filtered AC signal needs to be rectified. The rectified signal will cause an LED to flicker dimly so it must be filtered.

I have this fairly complicated circuit on my hard drive but it has some serious errors.

Look in Google for Color Organ Circuit and use just the bass part of it.
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top