SO lost! LM3916

[Ethan]

Long story short. I've been staring at this datasheet http://cache.national.com/ds/LM/LM3916.pdf for a while now and I'm more confused than ever. I just want to have an LED VU meter that acts like the analog equivalent to measure line level audio.

I get lost where it talks about Vref also affecting LED current, etc. Is the Vref refering to meter level calibration, or whaaaaaa?

Please help I'll be in the corner with my dunce cap on...

 

[ToshiroTamigi]

Hi Ethan,
here there is a project involving a brother of 3916, the lm 3915 that is a logaritmic meter with a resolution of 3dB per led.
I think this could be useful.
http://sound.westhost.com/project60.htm

To use with 3916 you could simply tie pin 8 and 4 to gnd removing r4.
R3 will set the leds current that will be ten times the current flowing trought R3
This will be equal to VRef/ R3 with VRef=1,25 that is the reference voltage at Pin 7.

You can adjust the VU meter with VR1

The Values at wich the varius led will lit are these (in dB referred to +3dB=1,25V ad pin 5 )
3 2 1 0 -1 -3 -5 -7 -10 -20

Wish this could help....

Alessio

 

[PRR]

Just wire it like shown on pg 2. You REALLY do not have to know all that other stuff.

But if you look around, almost nobody actually uses 3916. Quasi-pro gear usually has a row of LM339 comparators, a resistor string, and an LED current regulator.

 

[Ethan]

That's what I was looking for :grin:
Thanks!

 

[robomatique]

Two different approaches:

Standard:

http://electronicprojects.org/content/view/4//

Quad:

http://www.all-electric.com/schematic/quad-met.htm

Robert