smallest 5 led mono vu meter circuit diy?

[Jdansti]

Good point. You wouldn't want your robot shouting at your guests.

[deadastronaut]

ok, in my quest to find a good 'responsive' vu meter i found this russian guys version of the AN6884 VU METER..

1st vid is straight an6884 circuit...

2nd vid is with opamp added...(better peak and trough)

http://translate.google.com/translate?sl=ru&tl=en&js=n&prev=_t&hl=en&ie=UTF-8&layout=2&eotf=1&u=http%3A%2F%2Fcxem.net%2Fsound%2Flight%2Flight60.php

i'll add that to my breadboard, but i'll still need the electret mic amp too though right...

[deadastronaut]

ive given up on the AN6884 with electret mic....just couldn't get it stable..

soooooooooooooo....

ive dug out my lm3914 vu ic....running on 9v
http://www.ti.com/lit/ds/symlink/lm3914.pdf

ive tried adding the mic preamp to it, but i really have to tap the mic to get it to respond!!!...i upped the gain to 4.7M....still weak.

2nd scheme down..
http://www.head-fi.org/t/547933/q-how-to-modify-mic-pre-amp-to-higher-gain


any suggestions for an electret mic input to the 3914...running on 9v..?

[Jdansti]

Power your mic with this:



Then run it through an LM386 with the output to your VU?

[deadastronaut]

cheers jon, ive tried various preamps to no avail....

i found a guy who did it on video, but the his link to the schematic was dead...arghhhhhhh...

i just tried an opamp version and that didn't have it either...hmmmm....

i'll give that a go...


edit:  nope!...i can't believe a mic on a 3914 isn't more popular...unless nobody ever got it going of course. ...

looks like the last resort is i may have to just use the good old 386 on its own just to flash lights (sound 2 light...bummer)...i fancied a nice proper one..

[Mike Burgundy]

Rob, the 3194 wants rather high input voltages - the first datasheet example wants 5V for full LEDs. Line level is also quite easily achieved ( Minimum Vref is stated at 1.2V so you have some overshoot over 0dB which is 0.7V, or you are aiming at Pro line level  (+4dBu) which is a neat 1.2V).
So with R1 = 0 Ohms you have an internal reference of 1.25V. If you bring the mic level (which is something like 10-15mV) up to that level it should work. Amplification 100x.

[deadastronaut]

cheers mike, forgive me for being a dumbass, i'm not too au fait with figures.

are you saying the preamp will work with the 3914 pdf diagram?...if R1 is 'o' ohms...i.e ground?


i have the 3914 setup as in the pdf diagram (and below), but all leds are on even with or without an input on the 3914 at all..

i must be missing something? ....wouldn't be the first time..

[Mike Burgundy]

They shouldn't be on. At all. The R1 I was referring to was the one as per the datasheet, in your schem it's the 1K connected to pin7.
What's the AC/DC voltage on pin 5? For all LEDs ON, that should be 1.25*(1+(3k3/1k))=5.4V (or more)
There's something wrong, either faulty wiring or components, possibly the preamp is oscillating. It did work before, but didn't have any range, right?
Have a look at the voltage at pin5 (signal in)


Dang! That's what you get for ripping through a datasheet too quickly - I meant R2 so thets the 3k3, not the 1k. If R2 is (close to) 0, then (look at the formula) you'll get 1.25V range.
I'll have to dig deeper to see what R1 needs to be to satisfy the chip (I'm guessing there's limits), dinner time now.
Edit: plus, as was said before I think, I'm not sure if you need some kind of envelope thingy - the datasheet suggests it does it internally though. Now I'm gonne eat ;P

[deadastronaut]

enjoy ya dinner....

i think i may have fried my mic, i reduced the 10k to the mic to 9v by mistake...arghhh and smelt burning.  

it reads 64 ohms , but not sure if it'll still work....(i have another few on order anyway).


does that scheme above i did look ok, thats what i have on my board...?



anyway, i'll post my v's in a bit...cheers!.

pin 5 with nothing connected read 0.27v

all leds on...they go off when measuring...then back on.

[PRR]

> must be missing something?

My '3914 groove was decades back, but doesn't the signal input need a path to ground? Possibly 10K-100K?

Does "color organ" turn up any inneresting ideas? These will not be useful as a Level Indicator, but this is not for measurement. They were specifically designed for party use (in days when electronics were much more expensive (and sometimes rather reckless)).

[deadastronaut]

@prr:  its never too late too be groovy..

you were right, however my mic is definately burnt out...

so i rigged up my guitar (as schematic above, and now have a sound to light vu meter....btw i took pin 9 connection to pin 11, otherwise all led's were just on....hmmm

i put a 2.2k on the input to ground.....it responds nicely...i know ill have to adjust that when i get my new electrets, i'll see how it behaves then......probably tomorrow!.. ..but yep it works!!!..

now to try the 'dot' mode!....

cheers guys!!!!..

[Mike Burgundy]

so i rigged up my guitar (as schematic above, and now have a sound to light vu meter....btw i took pin 9 connection to pin 11, otherwise all led's were just on....hmmm

i put a 2.2k on the input to ground.....it responds nicely...i know ill have to adjust that when i get my new electrets, i'll see how it behaves then......probably tomorrow!.. ..but yep it works!!!..

Glad it's working, but whut?
Pin 9 to pin 11?
pin 11 is a LED port, pin 9 is MODE (9V - graph mode, disconnect - dot mode)
Now I'm confused as to what you did.

[deadastronaut]

ha ha so am i...

i found this 3914 'battery monitor' version....which takes  9 to 11...theres heaps of different 3914 configs out there, so its hard to find the 'right' vu one...

http://www.electronics-lab.com/blog/?tag=lm3914

i tried the pin 9 on/off dot mode...no joy...weird eh!..

[deadastronaut]

hmmmm...being the worlds greatest dumbass again..i was looking at the datasheet for the an6884 led vu meter...which is great btw., 

there is a high gain amp on the an6884 , pin 8 in, pin 7 out..

http://www.e-ele.net/DataSheet/AN6884.pdf

could this be used for sound too?...in some way?..just curious,...and dumb.

[gcme93]

could this be used for sound too?...in some way?..just curious,...and dumb.

Yeah I guess so? You'd just need to work out how to amplify your signal enough to make it register in the right range for detection. (You wouldn't want to use this amplified signal for anything else after though)

[earthtonesaudio]

Since the datasheet refers to it as a "rectification amp" it probably rectifies and smooths an AC input, causing the output to be more like the signal's envelope than the original signal. 

This is just me guessing though; give it a listen and let us know. 

[PRR]

> could this be used for sound too?...

The way it's biased, it must only amp half the wave. And for smooth bargraph, you also want the cap which now gives the envelope not the waves.

So it isn't a good audio amp.

[Jdansti]

^ But possibly by adding the cap (and/or other components) and mixing the envelope with clean signal, you get a potentially desirable effect???  (Probably not but it just sounded like something to experiment with). 

[deadastronaut]

hmmm...i'll have a poke around then...cheers.

meanwhile...heres a vero of the 5 led vu meter, i got rid of the trim, stuck 2 resistors in place instead, great little meter..

[deadastronaut]

and heres a 9 led version...