LED Volume Indicator?

[jishnudg]

Seen these in hi-fi applications (home theatre systems etc) where there's an LED array or something that shows the volume at which the music is playing,dynamically. Can a 9V version be made for stompboxes (just for visual appeal)...and I'm supposing some sort of trimpot must be present on board to fine tune the sensitivity of the thing..
Anybody tried this?

[Mike Burgundy]

Usually employs a dedicated chip, such as an LM3915.
google LED VU meter.

[deadastronaut]

lm3914/5

i had the 3914 and managed to get it as a volume level meter....haven't got the schematic now but checkout the datasheet for those..

another interesting vu meter chip is the AN6884. 5 led vu meter.

http://www.aronnelson.com/gallery/main.php/v/chickpea/5ledvumeterpcbDA2013.jpg.html

[hex_void]

Another way to build it is to use opamps. This is what I could come up with in 20 minutes.

http://www.aronnelson.com/gallery/main.php/v/Schematics-etc/VU_meter_opamp.jpg.html

The first two opamps form a precision rectifier, the third is used to create a floating ground to shift the signal level to 1/2 the power supply voltage and the rest are used as comparators.
I'll leave the resistor calculations to you. The potentiometer is optional. LED resistors should be 680R to 1k for 9V supply voltage.

[jishnudg]

Looks like the 3914 would be a more compact solution, right? Could I just use a trimpot so I can fine tune the VU meter to be sensitive to the preamp circuit behind it?

[jishnudg]

lm3914/5

i had the 3914 and managed to get it as a volume level meter....haven't got the schematic now but checkout the datasheet for those..

another interesting vu meter chip is the AN6884. 5 led vu meter.

http://www.aronnelson.com/gallery/main.php/v/chickpea/5ledvumeterpcbDA2013.jpg.html

Which resistor should I replace with a pot/trimpot for variable sensitivity?

[deadastronaut]

@jish:

for the an6884?..

look at the application circuit.

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

i swapped the trim for 2 resistors , 220k/330k...note: this is a vu meter, not a volume level meter.

[jishnudg]

Got it, thanks

[jishnudg]

Also, how do I make similar bar graph displays to, say, display a parameter that has been dialled in with a knob (say, Gain)...I understand that I may need dual ganged potentiometers for such a thing, which I'm okay with.

[Jdansti]

To clarify, are you asking for an LED array to show the position of the knob, or to show the output power. (I think you're asking for the former, but I'll ask anyway).

[deadastronaut]

heres a cool example of the lm3914.  with dot display too..

it would look cool around a pot with 3mm leds.

[jishnudg]

To clarify, are you asking for an LED array to show the position of the knob, or to show the output power. (I think you're asking for the former, but I'll ask anyway).

Both... my first query was regarding the latter (an array to show the output volume dynamically) and the second question was regarding the former - say I have a gain pot, can I have an LED array underneath it showing how much gain I've dialled in with the potentiometer - purely a visual element.

[deadastronaut]

ive always fancied these, no idea on what you have to put together to drive it though...looks cool eh!

a guy on here built one into his 'competition winning pedal'' i believe..

http://www.ebay.co.uk/itm/1-3-Annular-LED-Ring-Display-w-Red-Bars-Yellow-Dot-Rotary-Encoder-or-Clock-/281077952677?pt=LH_DefaultDomain_0&hash=item41718d30a5

http://www.ebay.co.uk/itm/1-3-Annular-LED-Ring-Display-Red-Bars-Yellow-Dot-Rotary-Encoder-or-Clock-/251243360872?pt=LH_DefaultDomain_0&hash=item3a7f457268

[jishnudg]

ive always fancied these, no idea on what you have to put together to drive it though...looks cool eh!

a guy on here built one into his 'competition winning pedal'' i believe..

http://www.ebay.co.uk/itm/1-3-Annular-LED-Ring-Display-w-Red-Bars-Yellow-Dot-Rotary-Encoder-or-Clock-/281077952677?pt=LH_DefaultDomain_0&hash=item41718d30a5

http://www.ebay.co.uk/itm/1-3-Annular-LED-Ring-Display-Red-Bars-Yellow-Dot-Rotary-Encoder-or-Clock-/251243360872?pt=LH_DefaultDomain_0&hash=item3a7f457268

This is Exactly what I was asking about Wanted to put this around all my pots...

[deadastronaut]

i can't seem to find a datasheet for those...hmmm...

might be tricky to fit...

[duck_arse]

if you had bi-colour leds around yr pot dial, it *should* be possible to use a single lm3914/5 with some input/output switching, to display yr pot setting in one colour, and yr output/signal/something level in the other colour.

[deadastronaut]

^ good idea!..

[duck_arse]

I don't know about "good". and I think you would need common anode bi-colours, or it would un-light the leds as the voltage increases.

the more I think about it, the less difficult it seems. and you could hang it on the xmas tree during the holiday period.

[mth5044]

Anybody have ideas besides an LED bar graph/line of LEDs? I've always fancied the Echorec's EM81 eye tube.

[merlinb]

Anybody have ideas besides an LED bar graph/line of LEDs? I've always fancied the Echorec's EM81 eye tube.

How about a DM160? 
http://s81.photobucket.com/user/merlinblencowe/media/CIMG4628.mp4.html?sort=3&o=55