lm3916 vu and dot..

[deadastronaut]

whats the best setup for the 3916 with guitar going straight in..?

heres the bog standard schemo:

  ....which doesn't react.

and here's how i have it now, so its sensitive for guitar (humbucker) going in..(not sensitive for single coils)

but then i lose the dot function...hmmmmmm..... ideally i woud like to have vu and dot functions..



ideas?..

[shrubbery]

I'm not sure what's the problem, humbuckers are louder but without boost I won't get near reference voltage either (I think that's ~1V RMS with 1.2k resistor).

What is dot function?  This IC has dot/bar mode but the only difference is that it lights up single LED in dot mode (eats less power).

Also have a look at this: http://sound.westhost.com/project60.htm

[duck_arse]

I dunno the lm391x are meant for guitar input. you'd need a buffer of some description, you could mess that about w/ a couple of resistors to pick between those nasty hummbuckers and those nasty singles. the datasheet suggest rectifiers.

there is a way to ?multiplex? the mode pin so that the dot holds the peak and the bar shows the average, or some such, was very popular in the eti circuits back when. is that what you mean by dot and vu?

[deadastronaut]

well apparently, if you connect pin 9 to v then it behaves as  a vu/bar meter...

when pin 9 is left open it goes to dot mode...  so you can choose either..

example.

https://www.youtube.com/watch?v=uz8IksRLopw

at 1:07 he takes off pin 9...

ive tried a buffer in front...no joy..

with the amount of times this chip gets recommended for guitar led fun use

i'm surprised there isn't a common guitar fun use schemo about....hmmmm....

[R.G.]

The LM391x chips will do either dot or bar, not both at the same time. They also will not do peak versus average. There are ways to mess about with the external voltage you feed them to get this kind of function, but you rapidly aggregate a lot of circuitry to do it. The base circuit reads peak amplitudes, but relies on the persistence of vision in the human visual system to "average" the brightness.

You really ought to use some kind of buffer to avoid any possible problems with loading on the guitar signal, and that then gives you the ability to muck with the gain of the buffer to match it to low versus high output guitars. If you leave it fixed, the 3916 does the obvious - it produces an output in log-ratio steps. A single coil is about 10-20db down from a humbucker, so a single coil is always down in the (mostly invisible) mud when the 3916 is set up for a humbucker. There are only ten steps it can produce.

You might want to look at ganging two of them for an expanded scale. It's in the app notes. This would extend the range so that single coil would be visible. Note that you can play games with ganging output pins and using steering diodes to make the output pull down pins on the LM391x series play games with which and how many LEDs are on. You might want to use two LM3916s for wider scale, but make each LED pulled down by two adjacent output pins so that you get double the range, but the same number of LEDs. There are many other tricks.

[duck_arse]

found a link to the eti I was thinking of:

http://www.google.com/url?url=http://www.epanorama.net/sff/Test_equipment/Meters/Wide%2520Dynamic%2520Range%2520LED%2520Level%2520Meter.pdf&rct=j&q=&esrc=s&sa=U&ei=DKw2VIvDEMT88QWupoK4BQ&ved=0CBQQFjAA&usg=AFQjCNEOeBSofaLIsTk11l37Hf5hR2E_ww

[deadastronaut]

@r.g,  i only have room for 10 x 3mm leds really for what i want to do with it..

so minimal the better really..


buffer?..i tried an npn buffer from amzfx , into it..no joy.

@da, hmmmm thats a lot bigger than i was hoping...

cheers guys..

[Mustachio]

Hey Rob, check out how merlin uses the lm3916 in the glassblower and the engineers thumb.

Looks like he uses a dual opamp in the glass blower with a few other components to feed the lm3916.

http://www.valvewizard.co.uk/glassblower.pdf

Scroll down to page 9 has the VU schem.

I remember playing with the lm3916 a few years back and I got it to work, but it was far from perfect , and then I think I knocked my breadboard into a large glass of soda pop haha.

We have funny timing, I just got 3 lm3916's in the mail today from Ti's free samples!

I was thinking about making one of those VU light towers.

[deadastronaut]

ahhhh brilliant, cheers jim / merlin..

i'll try that out today..

funny i got my 'samples' from them too...  ..i also messed with the 3916 a while back and never got it sorted properly...

so its well overdue...

yeah ive been looking at those towers too, very cool...

i ended up looking on ebay at plexiglass/perspex...i found a guy doing A4 2mm for £2.50,

so i got some for a volume pedal lightplate...bargain

but you can get some really nice thick stuff too 15mm etc.....cool.