Zee1usa

U.A.2.1.0.8. type Tri colored led circuit.
« on: July 02, 2004, 04:44:07 PM »
Hello,

 I was wondering if anyone has any info on this type of circuit.
 
1) Has any other company used this type of LED design?

2) I would love to use this type of circuit for a homebrew micpre
for fun.

3) If this is proprietary (classified ) information I will not
bother looking into this as I would like to be respectful
to the engineer who designed this type of circuit.

4) I am thinking this involves 3 LEDs some resistors
and a few capacitors. I dont know if any IC's are used?

5) Maybe Winston O' Boogie could comment on this?
I would appreciate it. If you would rather not offer
advise on this circuit I will understand.

Thank you
Quote from: "jrmintz"
Dave,
 The most important thing is to finish something and let it be heard instead of f*cking around making the "perfect" album for twenty years.


Svart

U.A.2.1.0.8. type Tri colored led circuit.
« Reply #1 on: July 02, 2004, 05:21:43 PM »
tri color leds are actually 2 leds in a single package.  usually one red, the other green, when both on they turn orange.  i think there are more choices these days though..  I don't know if that is what you are looking for but i thought i'd chime in anyway.

cheers
Welcome to the GroupDIY leper colony! when something falls off, we just replace it with a tube!
occupation: General Electron Mayhem

Alesis X2 information repository:
http://www.theopiumdenproductions.

Zee1usa

U.A.2.1.0.8. type Tri colored led circuit.
« Reply #2 on: July 02, 2004, 07:18:10 PM »
Hi Svart!

 Thanks for your reply. Actually I do know about a tri colored LED
in one package, but the one I am thinking of is I believe 3 seprate colored
LED's mounted together in the same lamp bulb kind of like one in  the UA 2108 :wink:


cheers n beers :sam:  :green:
Quote from: "jrmintz"
Dave,
 The most important thing is to finish something and let it be heard instead of f*cking around making the "perfect" album for twenty years.

mcs

U.A.2.1.0.8. type Tri colored led circuit.
« Reply #3 on: July 02, 2004, 08:16:48 PM »
Are you talking about RGB LEDs? You can get any colour by changing the current in the three LED chips in the package.

Best regards,

Mikkel C. Simonsen

Zee1usa

U.A.2.1.0.8. type Tri colored led circuit.
« Reply #4 on: July 02, 2004, 09:53:10 PM »
Quote from: "jrmintz"
Dave,
 The most important thing is to finish something and let it be heard instead of f*cking around making the "perfect" album for twenty years.

soundguy

U.A.2.1.0.8. type Tri colored led circuit.
« Reply #5 on: July 03, 2004, 02:39:46 AM »
what a good sounding box, winston did a fine job with that one.

1108's totally rule.  Probably my desert island preamp if I had to pick one.

sorry, nothing helpful to add about the leds...

dave

chips are good with dip...

PRR

U.A.2.1.0.8. type Tri colored led circuit.
« Reply #6 on: July 03, 2004, 02:51:40 AM »
"The SIGNAL indicator is a tri colored LED. It will be green when a low level signal is present, changing to amber, then red as signal strength is increased."

Simple conceptual reverse-engineering:

Rectifier, filter, giving a DC voltage proportional to the audio.

Two "window detectors". This is a comparator that gives a high output if the input is inside a certain voltage range, like "+2V to +3V", but is low for signals outside this range. A window detector is usually two comparators fighting each other.

One window detector might be set for "10mV to 1,000mV", the other for "100mV and up" (a simple comparator, not a full window detector). The first drives a green LED, the second drives a red LED, in the same place. From 10mV to 100mV you see just the green. From 100mV to 1000mV you see both green and red, looks yellow. 1000mV and up, you just get red. Taking 1000mV as "0dB", then green means -40dB to -20dB, yellow means -20dB to 0dB, and red means over 0dB. A useful range from "soft" to "loud".

With such a one-point tri-state indicator, rectifier action and filter speed may be critical to give useful indications. Too fast would be a muddy yellow. Too slow may give blips of red that are not noticed in the amber glow. Also the visual impacts of green, yellow, and red are not equal, so you have to fudge the LED currents for smooth transition.

So while we can guess a way to get a similar function, the fine-tuning could take a lot of experimental trial and error and judgement.

And while my straight-forward approach could work, I suspect that it could be simpler, even radically simpler. Straight-forward is probably best in DIY, but in Commercial Production you will work all night to design-out a penny in cost (either to reach a price-point or so you can put that penny where it will sound better). I'm wondering about a triangle-wave and a 2-pin tricolor LED. Not a lot more complex than the old neon lamps on lowest-price recorders.

U.A.2.1.0.8. type Tri colored led circuit.
« Reply #7 on: July 04, 2004, 02:23:14 AM »
Sir Winston O'Boogie Bell.
Jeffrey Toobin: "This is the most embarrassing week" ever.

Rudy Giuliani: "Hold my pants..."

Zee1usa

U.A.2.1.0.8. type Tri colored led circuit.
« Reply #8 on: July 04, 2004, 03:47:42 AM »
Thank you all for the comments on this as I really appreciate them.

 WOB- you may have cobbled this together...but I think my 2108 has the
*coolest* set of multi :oops: colored LEDS that I have ever seen.
 I like the frequency of them as they fade in and out.
 
I think it would be cool if you used this idea again in the future on another piece of gear.

Thank-you

Nick :thumb:
Quote from: "jrmintz"
Dave,
 The most important thing is to finish something and let it be heard instead of f*cking around making the "perfect" album for twenty years.

wowandflutter

U.A.2.1.0.8. type Tri colored led circuit.
« Reply #9 on: July 04, 2004, 06:48:01 AM »
Hey what was the deal with that mod that   they sent out to everyone
somthing abouout the led indicator sending a slight cklick?
Though I didnt hear the noise before i did the mod anyway.  
You probably know what i am talking about winston.


SSLtech

U.A.2.1.0.8. type Tri colored led circuit.
« Reply #10 on: July 04, 2004, 08:29:33 AM »
The old Aphex type B had a tri-colour LED for the 'Drive' setting... didn't someone just post that schematic recently...?

A word of caution on tri-colour LEDs: Neve used them in the V-series consoles to display dynamics-section gain reduction. -It seemed like a good idea. -However, when the combined action of a compressor with a typical release tail, and a gate with a similarly moderate decay would make the dratted thing useless. All that happened was that whether it was osed on something like a drum, or even an occasional backing vocal, the light would seemingly randomly flash different colours, and the engineer's brain couldn't draw any useful information from it.

Even on the Aphex, it was compact and cute, but ultimately not very easy to read.

There is a certain 'help' that the brain gets from seeing the LEDs in a spaced array, which allows the brain to 'read' the result much better.

The Neve situation was so bad that a company even manufactured an aftermarket metering solution with a pair of 'ladder' LED arrays per channel for compression and gating GR display. All Japanese consoles were specified with factory-original bargraph ladder GR metering, since the Japanese (very sensibly) absolutely refused to accept the original tri-colour LED nonsense.

The Neve application was worse because there were two signals acting upon the same tri-colour LED (Compression GR and expander/gate GR) and long periods of silence on a backing vocal (solid red from hard gating) would start flashing like traffic lights on acid whenever the gate opened!

Keith
"A waist is a terrible thing to mind"
Quote from: PRR
Ah, but that was 1999; we don't party like that any more.

U.A.2.1.0.8. type Tri colored led circuit.
« Reply #11 on: July 04, 2004, 01:15:49 PM »
Winston O'B Nobs 'n' a pot of tea for two please
Jeffrey Toobin: "This is the most embarrassing week" ever.

Rudy Giuliani: "Hold my pants..."

Mark Burnley

U.A.2.1.0.8. type Tri colored led circuit.
« Reply #12 on: July 04, 2004, 03:26:27 PM »
Aaah, sweet tea...

Anyone interested in looking at a 2-window comparator overload/signal present indicator circuit can have a look at Page 2 of this Rane schem:

Rane MS1 Schematic PDF

Very simple- basically a textbook window comparator.

Of course you can add more "windows" by extending the voltage-reference divider, and adding more comparators (or op-amps in this case  :roll: )

Watch out when buying a multicolour LED though! Make sure you get a three-lead device. If you get a 2-lead device it is a red and green LED connected in reverse-parallel. So you need an AC drive to make it yellow. A three-pin type has a red and green LED connected "nose-to-nose" as a common anode or common cathode. This way you can use the tri-state window comparator with diode-OR switching to get the result.

 :thumb:

Mark
O_O tape is life O_O

PRR

U.A.2.1.0.8. type Tri colored led circuit.
« Reply #13 on: July 06, 2004, 07:36:14 PM »
> 2-window comparator overload/signal

I don't think that is a window comparator.

Winston:

I didn't steal your colony: my folks were Brit, Scot, Irish in 1776.

Are the approximate threshold point a Trade Secret? Obviously they can be measured by anyone with this box, so it isn't a tightly guarded secret. Having some idea what levels are useful would help a clean-sheet design.

3915 is one way to do it. Seems like overkill, but the price is reasonable and the part is probably already in inventory (always a factor in production).

U.A.2.1.0.8. type Tri colored led circuit.
« Reply #14 on: July 06, 2004, 10:52:31 PM »
...
Jeffrey Toobin: "This is the most embarrassing week" ever.

Rudy Giuliani: "Hold my pants..."

PRR

U.A.2.1.0.8. type Tri colored led circuit.
« Reply #15 on: July 07, 2004, 02:29:55 AM »
I recall that the 3915 is tough to use except as intended (LED loads); still I don't see how that can work. But I didn't ask for the circuit. And amazingly enough, the 3915 is not as easy to find today as it once was; for one-off DIY I'd tend to use incredibly generic substitutable junkbox parts. After all, it is only a 3-bit ADC and super-slow as ADCs go.

Going by dim recall of how the 3915 is biased and what the outputs do, I get these levels:

0.4 to 1.8
3.1 to 6.5
9 and up

No real soft-threshold (there is a little built into the 3915, but with those gates on the output it will probably hard-switch).

You are using the full 30dB dynamic range (3915 is the 3dB/step version, isn't it?) so I can't get away with passive rectifiers.

I was curious if it went down to few-milliVolt level, which would rule out 10-cent comparators like LM339.

Oh and BTW: my very old DBX compressor has a tri-color LED to indicate under/at/over threshold. It is a narrow range of "at threshold", but if I play my levels right I can nail it on the loudest note of the movement without going "over". I forget how DBX did it, and a DBX box is a mini analog computer to begin with so this may be trivial for them.

Hah! Who wants a challenge? Do the "3-bit ADC" in vacuum tubes! Neon lamps, of course. Orange is standard, but there are green neons. Not sure what orange+green together behind frosted-glass looks like. Not a new idea: when RCA had those nasty ribbon-shutters for optical film sound, they built 10-step Neon "meters" because mechanical meters were too slow to avoid clanging the shutters.

Time for bed.

Mark Burnley

U.A.2.1.0.8. type Tri colored led circuit.
« Reply #16 on: July 07, 2004, 09:29:24 AM »
PRR,

Thanks for "the grumping"- it's not a window-comparator, but a 2-bit AD converter. Serves me right posting from memory rather than checking the schem  :oops:

I know the RCA neon-meter you're talking about- it's in the Audio Cyclopedia, and there is a block diagram. A bridging input feeds a buffer amp which feeds two voltage dividers with taps feeding the neon tube drivers. The neons are set at -45, -35, -25, -15, -10, -8, -6, -4, -2, -1, 0, +1 and +3.

There are no schematics, but if anyone is interested I'm sure I could put a pic of the block diagram up.

Retro VU bargraph- great!

Mark
O_O tape is life O_O

PRR

U.A.2.1.0.8. type Tri colored led circuit.
« Reply #17 on: July 08, 2004, 12:58:25 AM »
Here goes a first-hack.

The "ADC" is actually trivial once you get your head screwed straight to get the right voltages and polarities to the right pins.

Image part A

Six resistors, one $0.39 chip, and your LED(s).

This is a concept, not a Popular Electronics schematic. The three batteries would really be taps on a resistor voltage-divider network, pin numbers not picked, supply bypassing not shown, etc.

The LM339 is fed from +15V and -15V (not ground).

The voltage steps are rough guesses. They can be changed to suit your taste by fudging the resistor network (not shown).

The LEDs are fed a little funny. Logical would be to wire them to ground and switch the current on and off. But that dumps clicks in the ground, a bad idea. Many designers wire the LED from V+ to V-, never letting LED current into ground. (Not always an easy design.) To go a little further: don't switch the current on and off, leave the current running and short-out the LED when you want it dark. All of this is "wasteful", eating about 1/3 Watt all the time, but leaves ground quiet and supply rails quite clean. Instead of 6mA clicks in ground or supply, we have 0.3mA clicks.

The next trick is the LM339. This is an open-collector comparator, very widely used (i.e. available now and in the future). The open-collector means we can "wire-OR" the outputs, doing a little logic without extra parts. In this case the green LED is Off if the bottom 339 sees less than 0.4V, OR if the middle 339 sees more than 5V; otherwise the green LED is On. A true Window Comparator. (The Red LED just comes on above 1.5V.) Result:

Image part B

Input DC voltage across the bottom, labeled in dB, arbitrary reference level. Vertical scale is voltage on the LEDs: at 1.6V they light, less than 1.6v they go dark.

You "could" feed raw audio into this, but it would be dim, too much green, and half-wave. We need a rectifier and filter to smooth out the audio so the slow eye can make sense of it. There are a zillion ways to do this, but I am liking this idea stolen directly from National Semiconductor's LM3916 data sheet:

Image part C

Originally this was unity gain and DIN PPM balistics. The red scribbles are my suggestion for a gain of 5 (so the sloppy LM339 does not have to switch on very low levels) and a somewhat faster (more VU-like) decay for more lively action. You can fiddle this to your taste, or use another rectifier and filter.

{EDIT: updated image-links -PRR}
{EDIT: updated image-links AGAIN... thank you, Brian :( -PRR}
« Last Edit: October 27, 2013, 06:25:00 PM by PRR »

PRR

U.A.2.1.0.8. type Tri colored led circuit.
« Reply #18 on: July 08, 2004, 03:54:41 PM »
Here is a plan showing a test-session variable resistor divider.

The divider:
3-LED-e.gif

How it connects:
3-LED-d.gif

Starting with all pots centered, feed signal. You should get 3-color action.

Feed a very strong signal and trim the Yel-Red pot for "Red is way loud".

Feed a small signal. Trim the "Grn" pot for "Green means weak signal".

Feed a just-right signal and trim the Grn-Yel pot for "Yellow is just right".

For DIY one-offs, you might leave the pots in. For multiple copies, when you get the settings set, measure the three voltages (and supply voltage). Then figure the voltage differences. Multiply those by 1,000 (or 1K) and find the nearest resistor values. Say you got nice LED action with 0.32V, 1.47V, and 5.8V, with 15V supply. The scratch-pad looks like this:
3-LED-f.gif

10% variations are only 1dB differences, so I would try 10K, 4.7K, etc, instead of those oddball values.

{EDIT: updated image-links -PRR}
{EDIT: updated image-links AGAIN..... -PRR}
« Last Edit: October 29, 2013, 12:55:49 AM by PRR »

TomWaterman

U.A.2.1.0.8. type Tri colored led circuit.
« Reply #19 on: July 08, 2004, 06:39:06 PM »
Hi!

That is awesome stuff PRR - will be on the right click - save as ala Kev!!

Thanks Tom!

 :guinness:


 

Related Topics

  Subject / Started by Replies Last post
6 Replies
2468 Views
Last post June 14, 2012, 11:48:57 AM
by okgb
0 Replies
1094 Views
Last post November 18, 2008, 07:54:20 AM
by Steve Jones
10 Replies
3316 Views
Last post December 13, 2008, 04:38:43 AM
by helterbelter
20 Replies
7724 Views
Last post August 09, 2013, 04:22:16 PM
by tv