Vintage LED's - Page 1
Forum section: electronics / projects

author: zingzang
author_rank: Contributor
timestamp: January 09, 2019, 12:26:58 am
content: Hey Everyone,Came across EEV while searching for vintage LED's for a "history of LED" display I'm working on. I've amassed quite a few older LEDS; Monsanto's, fairchilds, national semiconductor, western electric, even a few from Texas Instruments.My ultimate goal is to make a small desktop/wall display that shows the evolution of LED's over the past 50 years. I'm hoping that an arduino will be able to drive all the LED's at their respective voltage while also demonstrating the unique qualities advance LED's have: color-changing, multidie, blinking, etc.Once I get a microscope objective for my camera I'll be photographing these to post along with the history I can find out about them.One such find so far has been a TIL209 made by Texas Instruments. In my hunt for old stock LED's I talked with a gent that had heard of a unique LED die designed by TI that was eventually packaged in a standard T1 casing. Thanks to a generous, kind, and older circuit designer I finally got my hands on some and they are indeed unique. It looks unassuming and modern at first glance but the die is on a larger platform/anvil than usual (for that period.) Very neat to be able to find the connection between stories/facts you hear while on this peculiar hunt.Does anyone have any experience using any of the modern micro-diy-computers to drive vintage LED's? Anyone find any really old specimens?

author: coromonadalix
author_rank: Super Contributor
timestamp: January 09, 2019, 01:11:21 am
content: You could use simple up / down counter ??You know the important thing is, to have the right voltage and current settings to drive your leds ......... check all the specs.

author: zingzang
author_rank: Contributor
timestamp: January 09, 2019, 01:16:00 am
content: Thanks. Yes, I've learned the hard (or fun way depending on your POV) that higher voltages = super hot LED/dead LED. Some of the ones I've found don't have data sheets available but it seems like red's take low voltages than yellow/green - atleast with the old ones.The vast majority of the ones I've come across so far seem to handle a short test with a 3v coin cell. Can output voltage be adjusted on the pin-outs or would it be better to use resistors for any outliers?

author: jeroen79
author_rank: Frequent Contributor
timestamp: January 09, 2019, 02:03:05 am
content: Resistors to limit the current would be most practical.Adjusting the input voltage to be in exactly the right spot on on the diode's I/V curve would be much more complicated.A 3V coin cell has an internal resistance high enough to limit the current.

author: Edison
author_rank: Frequent Contributor
timestamp: January 09, 2019, 02:08:28 am
content: The first LED made in Czechoslovakia

author: mvs
author_rank: Frequent Contributor
timestamp: January 09, 2019, 02:12:12 am
content: Quote from: zingzang on January 09, 2019, 12:26:58 amI have some where soviet red and green 0.1-0.2mcd LEDs in metal can (AL102 series). They were produced in '80s, but design is from the mid '70s.

author: james_s
author_rank: Super Contributor
timestamp: January 09, 2019, 02:34:56 am
content: That's pretty cool. Yes a microcontroller will work fine to drive the LEDs, the important thing is to select an appropriate resistor to limit the current of each LED or group of LEDs. Then if you want to control them individually I would suggest looking at the 74HC595 shift register, you can daisy chain as many of those as you want and control them easily from 3 pins of a microcontroller.

author: amyk
author_rank: Super Contributor
timestamp: January 09, 2019, 03:21:14 am
content: You may find this site very interesting:http://www.ledmuseum.net/museum.htmNote that some early LEDs used very different (much higher) voltages than the 2-3V of the ones today, and some others had very strict and small current limits, so it's best to find the specs before trying.

author: rrinker
author_rank: Super Contributor
timestamp: January 09, 2019, 06:13:48 pm
content: Fran Blanche has a YouTube video where she shows off a bunch of vintage LEDs she's collected. Actually there might be more than one now that I think about it.

author: spec
author_rank: Frequent Contributor
timestamp: January 09, 2019, 10:04:49 pm
content: Hi zingzang,I can remember when LEDs first became available at a reasonable price.Not sure if you already know this, but the best and most reliable way to drive a LED is with a constant current, rather than a constant voltage.

author: zingzang
author_rank: Contributor
timestamp: January 10, 2019, 01:46:27 am
content: Thanks for the info guys! I've emailed Fran begging/propositioning her to trade old LED's with meI hope it goes without saying that if anyone comes across any extras they'd be willing to part with, please, speak up or contact me. I'm a reasonable guy.Quote from: spec on January 09, 2019, 10:04:49 pmI'm not sure if I know that - you mean DC verse AC but I was under the impression that DC current is constant and that the only issue in my situation would be not to feed too much voltage into them. I'm a novice with electronics so feel free to teach me what I'm missing!Quote from: jeroen79 on January 09, 2019, 02:03:05 amThat's why I love em! I've tested many older LED's with a 3v without many negative consequences. One exception is a TIL 209 LED made by Texas Instruments whose epoxy cracked after a second of contact at 3v. Needless to say I'll be more careful with the remain 209's. Talk about brittle epoxy!Quote from: mvs on January 09, 2019, 02:12:12 amI come across these on ebay quite often. It looks like the soviets had a "if it ain't broke don't fix it" mentality with LED's as there seems to be 100x as many older style soviet LED's than there are US manufactured ones.

author: james_s
author_rank: Super Contributor
timestamp: January 10, 2019, 01:57:44 am
content: Quote from: zingzang on January 10, 2019, 01:46:27 amNo, AC vs DC has nothing to do with it, LEDs are DC, ignoring special purpose types. Perhaps a better term to use here would be "limited" current, you don't feed voltage into an LED, the voltage pushes current through the LED. You have to have a resistor to limit the current or the LED will try to draw as much as the source can provide. To calculate the resistor value you need to know the forward drop of the LED in question, then you subtract that from the supply voltage and plug the results into Ohms law. If you don't know the forward drop, you can measure it by using a resistor that will limit the current to something you can be reasonably certain is safe, like under 1mA then just measure the voltage across the LED.

author: zingzang
author_rank: Contributor
timestamp: January 10, 2019, 02:03:58 am
content: Quote from: james_s on January 10, 2019, 01:57:44 amAh gotcha! Thank you for the info. I knew I'd need resistors but I see what your saying now. I'll try the test you suggested on the mystery LED's (or the ones I can't find data sheets for.)Incidentally, I only learned about forward voltage a few months ago while hunting. I came across a strange LED (still in packaging) that was backwards. It was indicated on the packaging so it wasn't a manufacturing error. Turns out it's likely a TI led that is yellowish-green at higher volts but turns orange-red as voltage decreases. The guy who told me about the TIL209 mentioned he'd heard of such an odd LED when he was starting out there back in the day.I'm guessing it was intended to be a cheap/simple battery meter? No expensive logic to deal with and only one LED needed... could see it being used in a calculator or radio to let the user know the batteries were running low. Maybe?

author: spec
author_rank: Frequent Contributor
timestamp: January 10, 2019, 04:55:26 am
content: Quote from: zingzang on January 10, 2019, 01:46:27 amOK No problem.No not DC versus AC- just DC.The forward voltage of a LED for a given current is indeterminate and varies from sample to sample even of the same LED type and from the same batch. The forward voltage is also dependent on color, age, and temperature, especially with the earlier LEDs.The main objective with a LED is to have it look as you like, in terms of brightness etc. But once again, there are more variables in this because the efficiency of LEDs also varies quite a bit. With early LEDs the variation in brightness is quite large as is the beam angle.So the best way to illuminate a LED is to feed a defined DC current through it (in electronics this is called a constant current). The LED will then be able to have whatever voltage across its pins that suits it at a particular brightness and temperature.You can generate a semi constant current by putting a resistor in series with the LED and connecting the circuit to a DC voltage, but this is not very accurate unless the voltage is relatively high. Or you can use a simple circuit to generate an accurate constant current. Note that although the current is constant, it can be set to any value that you like, within reason that is. But once set the current stays constant irrespective of the LED forward voltage and any changes in the LED forward voltage with temperature etc.Quote from: zingzang on January 10, 2019, 01:46:27 amIt would be harder than that.Quote from: zingzang on January 10, 2019, 01:46:27 amAfraid this is not true.

author: spec
author_rank: Frequent Contributor
timestamp: January 10, 2019, 05:31:19 am
content: + zingzangJust to get the scope of this project:Can you say what the maximum number of LEDs on display will be?Will you want the LEDs to be illuminated one at a time or simply all on, or perhaps any number of LEDs on and any number off in any combination?Will you want to vary the brightness of the LEDs. If so, all together, or individually in any combination?Will you be displaying any modern high-power LEDs (say 1W) as a contrast with the older LEDs?What will be the power source: battery or mains?

author: CatalinaWOW
author_rank: Super Contributor
timestamp: January 10, 2019, 06:45:29 am
content: You have some real human factors challenges in your project. I have some very early red LEDs and by today's standards they are nearly invisible. If any modern LEDs are on the eyes will adapt to make them invisible in reality. As I recall the instantaneous dynamic range of the eye is about 40 dB which probably definitely doesn't cover the brightness difference between high power illumination LEDs and those early units.

author: cdev
author_rank: Super Contributor
timestamp: January 10, 2019, 03:26:32 pm
content: I have a bunch of old LEDs in a bunch of different colors/shapes that I got from the estate sale of an engineer neighbor/silent key.One thing thats useful about some of them, especially the 7 segment displays, some make pretty good varactors when back biased, they act like variable capacitors. (not emitting any light)This property is not consistent from one to the next, some are substantially better than other identical displays.

author: zingzang
author_rank: Contributor
timestamp: January 10, 2019, 09:22:44 pm
content: Quote from: spec on January 10, 2019, 04:55:26 amExcellent write up! Thank you. I'm not terribly concerned with getting the exact voltage for maximum brightness so I'll likely error on the side of caution. The early LED's are still pathetically weak compared to modern (or even late 70's) LED's so they'll look underpowered either way.Quote from: spec on January 10, 2019, 05:31:19 amAiming for somewhere between 10-20 but it could end up being fewer than 10 depending on what display case I go withUnknown - I've thought about keeping it simple and having them all power on at once. But with the abilities that come with arduino I have been thinking of having a delay between LEDs.Probably not for most of them. There is one LED that is yellow at peak voltage but turns red as the voltage decreases - I'd like to have that bad boy cycling to show off the feature. The other LED's that change are either 3 wire (so just alternating between one die and the other or they have an IC built in (a slow blinking LED I had.)Probably not anything that powerful. I have a few early white LED's but they aren't that bright. I'm still deciding what post-2000 LED's deserve to be included. I'm focusing on 3mm and 5mm LED's so I'd like to avoid the SMD super bright LED's.Most likely battery but that could change if I need more powerI'll be consulting with everyone here as the build progresses so stay tuned. Probably won't even begin to play around with the circuits until next month.Quote from: CatalinaWOW on January 10, 2019, 06:45:29 amAgreed. Thats why I'll probably leave out the high powered LED's. I did find an individually addressable 5mm from one of those neopixel websites that I feel fit's in with the T1's (the classic "bullet" shaped LED) If the brighter LED's wash out the dimmer one's then I'll likely resort to having the series of LED's light-up on a delay.Quote from: cdev on January 10, 2019, 03:26:32 pmInteresting effect. I've not messed around with the 7-segments much but I have seen first hand the unusual qualities some of these LED's have.

author: zingzang
author_rank: Contributor
timestamp: January 10, 2019, 09:31:26 pm
content: Forgot to mention that I was going through some new arrivals and found a bi-polar red LED. Both dies are red (the anvils are a cool design) but I'm wondering why go through the trouble of designing it?I get if one of the dies were a different color - that way reversing polarity would produce a different color. But why have two identical dies? Was this an attempt to power LED's using AC?

author: james_s
author_rank: Super Contributor
timestamp: January 11, 2019, 01:24:22 am
content: Yes, there have been a number of LEDs made for use in AC that have two dies in them. It solves two problems at once, producing light on both half cycles, and protecting each other from reverse voltage. Many early LEDs are easily damaged by reverse voltage. They are also not very bright so need all the help they can get.

author: cdev
author_rank: Super Contributor
timestamp: January 14, 2019, 10:10:59 pm
content: probably a way to have a light that just required a resistor to work with AC.Quote from: zingzang on January 10, 2019, 09:31:26 pm