LED forward voltage tolerance

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JohnRoberts

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At Peavey we made one old technology tube limiter (AMR VCL/2). It was basically a dual mono limiter with no attempt at matching gain elements. We had some customers add a stereo link capability but I make no claims for stereo imaging.

JR
 

Baderjoe

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I just bought a bunch of LEDs. This evening I tested 20 nominally identical RED LEDs with my Peak ATLAS tester which feeds a precise 5mA though them. The forward voltage drop ranged from 1.88V to 1.92V which is a range of just 0.04 volts. This compares to the 0.2 volt range I saw when testing five Vactrols. I remain suspicious of the Vactrols.

Cheers

Ian
You must keep in mind that LEDs are sorted by bins. That binning can be by forward voltage, color or light intensity. You may be measuring LEDs from a single bin. That might explain the tight grouping of the forward voltage.
 

Script

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If you want any kind of repeatability, like maximum GR ot just having the correct markings on the front panel
I don't trust faceplate markings (timing, ratio) one iota ;) but would expect a dual-mono and even a stereo-linked unit to be reasonably L/R matched (or at least user-matchable).
 

ruffrecords

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You must keep in mind that LEDs are sorted by bins. That binning can be by forward voltage, color or light intensity. You may be measuring LEDs from a single bin. That might explain the tight grouping of the forward voltage.
Thank you. I did not realise that. Presumably there is some indication of this on the LEDs themselves or their data sheet?

Cheers

Ian
 

gyraf

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datasheet usually only give a general range aimed-for in production.

batch is sold, the "good" ones kept and the unusable ones returned or sold to next buyer and so forth, until you have the really unspecified stuff left - which it will make sense to use for cheap vactrols where no one will ever see the light

When I surveyed the chinese vactrol market in 2016/17 I was honestly shocked about the spread (poor tracking, poor quality control) of just about any parameter I cared to measure. This to a degree where the different brand- and model numbers showed zero correlation to parameters like timing and resistance-vs-current

I hope it's gotten better somehow - it's actually not even in theory possible to make it worse than it was :)

/Jakob E.
 

Script

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How about buying only photoresistive cells from AliExpress... and then experiment with (red) LEDs. Shouldn't be worse than what they offer as finished optocells (often unclear over there what they are from description).
 

ruffrecords

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How about buying only photoresistive cells from AliExpress... and then experiment with (red) LEDs. Shouldn't be worse than what they offer as finished optocells (often unclear over there what they are from description).
That thought has certainly crossed my mind. About a year ago I corresponded with another member of groupDIY who wanted to make a Vactrol based compressor. In the end he found the off the shelf Vactrols to be very poor so he made his own with much better results - so this is indeed still an option.

Cheers

Ian
 

Audio1Man

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Some years ago I designed for a company that built stereo compressors. They used Vactrol’s and had a crude way of selecting them and many DUT unusable. I designed a test system for selecting them and it is still being used.

The system was an AP System 0ne, DCX-127 and a special test box. The program pulsed, timed & delayed the DUT to get it out of the dark mode. Then continued testing the cells for matching parameters. They were selected into about 70 different bins.

I used current mode in this system and didn’t need forward voltage matching.

Duke
 

Lee_M

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the LDR part of the vactrol (for technical reasons) always contains cadmium in amounts exceeding what can be rohs-certified for sale in EU (100ppm, 0.01%) - Compliance FAQs: RoHS
They should manufacture them in a nice metal can with a thick glass lens over the CdS cell, so that the CdS accounts for less than 0.01% of the total weight :cool:
Several companies - including xvive - has claimed to have ROHS-compatible solutions, but it always turns out to be outright lies. A company named Macron even presented falsified laboratory records to the EU group in charge of rohs/weee
Are you referring to the Xvive 5C3-R vactrols? I've seen those around online, I wasn't aware they were bullshitting about the RoHS compliance.


Luckily almost everything I build is for personal use (honest, officer!) so I generally don't worry about the RoHS side of things.
 

JohnRoberts

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Zep is pretty awesome. EaCo Chem Britenol HD is a big step above but it's pretty potent. Actually pretty safe, safer than their One Restore which will etch the glaze from tile, but cuidado still.
Oxalic acid (barkeeper's friend has this), White Ox...etc.....is great for rust stains....
I am finished with first quart spray bottle of ZEP and working on the second.

I ASSume that Britenol is a stronger concentration professional version...

I started out old and tired, so I am getting more tired of scrubbing. My shower walls are indeed getting cleaner but there are decades of hard water build up and I'm only down a couple decades.

I think I have heard you mention pumice stones for cleaning? Any thoughts about steel wool?

JR
 

gyraf

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They should manufacture them in a nice metal can with a thick glass lens over the CdS cell, so that the CdS accounts for less than 0.01% of the total weight :cool:

Are you referring to the Xvive 5C3-R vactrols? I've seen those around online, I wasn't aware they were bullshitting about the RoHS compliance.
No, that won't work off course - would have been done long ago.
The catch is that Cd content is specified in "separaple compounds" i. e. What you can scrape off with a lab-grade knife. And as the cadmium sulphide needs to be at some sort of a surface (to react to light) , it will always exceed the limit. Believe me, people have been working this for a while, but no solution...

Jakob E.
 

scott2000

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I ASSume that Britenol is a stronger concentration professional version...
Hard to say. I was surprised to hear Zep was Glycolic acid. Zep facials?...lol
Britenol doesn't really smell anything like Zep whatever that means. It's pretty great. Use it in sections with some abrasive stuff like barkeeper's friend or whatever and it works quite a lot better than zep using the same technique...working/rinsing sections just to be safe. I usually just keep a small bucket of water with a (green scotchbrite is potent) scrubby and keep it wet enough to make powder or whatever easier to work.

it's pretty industrial stuff. That Eaco Chem Company has some incredible chemicals. Their One Restore and Cleansol BC are others I'm also familiar with.... I think they sell samples...


I started out old and tired, so I am getting more tired of scrubbing. My shower walls are indeed getting cleaner but there are decades of hard water build up and I'm only down a couple decades
Chemicals can replace much of the labor but, at some point, mechanical removal is necessary. Pool tile guys use glass bead blasting to work off deposits along the water line for instance... I've used a DA sander in showers before with some aggressive compounds like stone scrub...... Wonder if pumice sticks/stones would do anything to shower tiles. Seems they would. Would like to test that .... I used to flip rentals for some investors to sell back in the 2000's boom and dealt with some pretty nasty showers...
Replacing them was common.
Some of those grout cleaning companies do some pretty amazing work with tile restorations too. Groutsmith is one here and other places..Pic is from one of their TX locations.... Maybe there are some near enough to you.
Maybe even spring for a new shower. Can make it a handicap/curbless floor with a seat and even a couple of bars.... Already fancying one for myself.... ;)

Any thoughts about steel wool?
Have an airline pilot friend who says they use the fine type and vinegar for the airliner glass. Never had too much luck with it where I've tried using it and the rusting of it was aggravating. But it seems like it should work in theory with some things....

Veer...lol
 

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JohnRoberts

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Hard to say. I was surprised to hear Zep was Glycolic acid. Zep facials?...lol
yup, mild acid and pretty skin friendly
Britenol doesn't really smell anything like Zep whatever that means. It's pretty great. Use it in sections with some abrasive stuff like barkeeper's friend or whatever and it works quite a lot better than zep using the same technique...working/rinsing sections just to be safe. I usually just keep a small bucket of water with a (green scotchbrite is potent) scrubby and keep it wet enough to make powder or whatever easier to work.
Barkeeper's friend is oxalic acid, so oxidized glycolic acid... I don't have any BKF sitting around, all I have is comet powder, and that doesn't play nice with acid (could release chlorine gas). I need to order some BKF
it's pretty industrial stuff. That Eaco Chem Company has some incredible chemicals. Their One Restore and Cleansol BC are others I'm also familiar with.... I think they sell samples...
I still cant find Britenol for sale. But I haven't asked my professional friends. This is quickly becoming moot.
Chemicals can replace much of the labor but, at some point, mechanical removal is necessary. Pool tile guys use glass bead blasting to work off deposits along the water line for instance... I've used a DA sander in showers before with some aggressive compounds like stone scrub...... Wonder if pumice sticks/stones would do anything to shower tiles. Seems they would. Would like to test that .... I used to flip rentals for some investors to sell back in the 2000's boom and dealt with some pretty nasty showers...
I have a pressure washer that I typically only use outdoors.. It might do something interesting on my shower, but I need to hurry, the shower is almost clean already. :unsure:
Replacing them was common.
I seriously considered reskinning my shower but I am too cheap... ;)
Some of those grout cleaning companies do some pretty amazing work with tile restorations too. Groutsmith is one here and other places..Pic is from one of their TX locations.... Maybe there are some near enough to you.
Maybe even spring for a new shower. Can make it a handicap/curbless floor with a seat and even a couple of bars.... Already fancying one for myself.... ;)
My shower walls are already night and day cleaner, after I have already consumed the first 1 quart spray bottle of Zep. Now I am working on the second quart bottle. Since I am single I could just declare my shower clean now (It was clean enough for me the last few decades). :cool:
Have an airline pilot friend who says they use the fine type and vinegar for the airliner glass. Never had too much luck with it where I've tried using it and the rusting of it was aggravating. But it seems like it should work in theory with some things....

Veer...lol
I have some cheap steel wool soap pads. I haven't tried them yet in the shower...

I sometimes use white vinegar (acetic acid) in my carpet shampooer, works like a charm. I also soak my bare feet in a dilute white vinegar solution to clean out toenail fungus (5 minutes per foot, once a day).

Thank you

JR
 

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