What's the problem? my LED project.

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Old 07-25-16, 03:34 AM
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What's the problem? my LED project.

What's the problem with my LED ?I t can't light on.
Hello, I'm Maydorifive ,I'm very happy to be here to discuss my problems and with all of you .
That's very nice if you could help me solving my obstacles.I'm a newbie so my question could be very simple.Please don't laugh at me .Thanks a lot!

I want to make a bigger project, but I have run in to a problem that I do not understand. I want to make an LED flash to music, for use in a bigger project. I have looked at about 20 different tutorials and googled my fingers off, because I cannot make it work. I can't light my LED.
I am using a 2N3904 transistor like him. I have tried with several jack sticks. I am simply lost, please help.
Firstly, I measureed it to make sure it is the case. the LED was connected with the right polarity. It's working at all . It does work, if I touch the base with the collector side, the LED lights up.
I don't know where did I wrong or do i use the wrong transistor? Or plus one transistor can light it up ?
, but I have tried everything, and I cannot understand why it is not working. It does work, if I touch the base with the collector side, the LED lights up. the battery's voltage is :It's powered with 3.3V from arduino, there is a resistor before the LED so it won't fry, that resistor is 100 ohm.
Solution 1 : Should I also add a couple of resistors - in series to LED and to the transistor gate.
I find that most likely audio not getting about the 0.7V needed on the base of the transistor.
So , Solution 2 change the transistor
Solution 3 :
The circuit can't work out without amplifier. Do I need to find another audio source with higher signal amplitude? Or can my laptop work? Will that help my LED worked ? But unfortunately I do not have an oscilloscope, I will try another audio source.
Thanks in advance! I really appreciate any help!
Regards,
Maydorifive

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  #2  
Old 07-25-16, 07:12 AM
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Try adding a 560K resistor from base to +3.3 and a 100k resistor from base to common. Then feed the audio through a 1 uf capacitor to the base and junction of resistors.

The resistors will bias the transistor to about .5 volts so it is closer to turning on, and the capacitor will AC couple the audio.

You may have to tweak the values a bit. Good luck!
 
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Old 08-01-16, 01:42 AM
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Thanks for your advice. I have made it work successfully.
 
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