So i dont even need my 10k pot? cuz i cant see that in this circuit? or should i just add one more pot

Just wire it up as Bertus shows. Then let us know if you get the full dynamic range when connected to your PC audio.

 

Hello,

Here is your circuit again, now I have drawn the 100K pot in YOUR GIVEN schematic.

Put the 10K pot at minimum value (the wiper all up) and adjust the 100K to meet your sensitivity.

Bertus

 

Yo thank you guys so much i dont have 100k pot right now il go to the market tommorow and grab it

 

Hello,

Do you have other higher value pots?
An 250K or 500K will also work.

Bertus

 

nope ;/ i bought parts only for this project. Im doing electronics only for like 2 weeks , so i dont have many parts laying arround ;D

 

Hello,

You told us that only 4 leds came on.
With the 100K you should just reach the full range.
When you want to make it more sensitive, use a 250K pot.

Bertus

 

yeah.. il try and post u result

 

You can also add resistors of various sizes to get what you want. You should be able to light one more light every time you double the value of the resistance of R2 (pot or fixed value resistors)

 

Wait i think i got it wrong? So i thought that i need to lower resistance to get all the leds lightining? And u saying i need to increase resistance?

 

Hello,

I think he means to say something like in the following schematic:

You can adjust the sensitivity now with R2.
I have drawn a 220K resistor in the schematic, but any value higher than 100K will do.

Bertus

 

i put 470K oms resisotr nothing changed at all

 

Hello,

The 470K resistor is between pin 6 and 7.
Did you turn the potmeter R2?
Can you post a picture of your set-up?

Bertus

 

I didint changed anything just added 470K resisotr between 6 and 7 pins. I dont think so u will be able to see anything from my breadboard. Alot of wires ant stuff

 

Hello,

Try to put pin 8 to ground.
With the 470 K between pin 6 and 7, you should be able to get a full range of leds.

There may be a problem with your small 9 volts battery.
Could you check the voltage on the battery with a multimeter?

Bertus

 

i dont have one ;/

 

still the same thing. connected pin 8 to ground. nothing changed at all. Maybe i need amplifier to increase my sound power?

 

Let's cover basics first.
Sound along a line cable is just a varying voltage. The LM3915 measures voltage. It's rigged so that it will drive LEDs as that voltage increases, hence louder sounds = more volts = more LEDs.

The lowest "full scale" voltage you can realistically get is 1.2V - so you'd need 1,2V signal in to get all LEDs to light. That's fine if your audio source is a professional level unit (for example a PA system or mixing desk)... but it's not. It's consumer level (home audio equipment, like CD players, Hifi, PCs etc.), so likely max out is around 0.7V

This ties in with what you are seeing - at it's minimum 1.2V scale, 0.7V is about half, hnce only half the LED light up.

You need an amp to boost the voltage - I'd suggest something like a basic op-amp with a gain of around 10x. That will make your 0,7V up to 7V, and you can then use the pot. to adjust the sensitivity as required.,

When you've got that going, you can even duplicate the circuit an look at "passive filters" to make a spectrum analyser - they're REALLY cool!

 

...oh, and buy a multimeter. Seriously - one of the most useful things you can have when doing electronics.

 

This ties in with what you are seeing - at it's minimum 1.2V scale, 0.7V is about half, hnce only half the LED light up.

The LM3915 has a log response so 0.7v on a 1.2V full scale should light up 9 out of 10 LEDs. I think the OPs problem is that he has the V(HI) reference set too high and needs to get it down to 1.2V as you suggest.

 

True, but that's peak, not rms, and the chances are the unit is nearer to rms (since that would be easier to ead and understand on a VU meter). Typical rms off of consumer grade audio playing music is around 0.32V which would be 6 LEDs, and the PC sound card probably has a lower output than that to allow overhead when mixing multiple sources in the software mixer. Yes the mathematical rms is 0.8V, but unless you're listening to heavy metal through a brick-wall limiter, you're not likely to actually see that produced.