LED 4-Pin help needed

Question

I could use some help choosing replacement 4-pin RGB lamps for my In Motion outdoor Xmas sets. I have 20 twelve-lamp “C9” sets on the house, end to end, each with a control module. They manage to stay in synch, so the modules must be absolutely identical electronically. Color combinations and solids rotate in sequence and can be steady or flash, etc. The colors include white, purple, orange, etc., not just RGB, so the controllers apparently mix RGB with varying current I assume.

When new I had sets that acted up, with sections of 3 or 4 lights staying solid white, or occasionally groups of lamps entirely out. The mfr. ultimately sent me more than 20 new sets, so usually now I just replace an entire faulty string with one of those, and later try to fix the original. But that’s a nightmare, and I now have 7 or 8 sets from years past clogging my workbench. Sometimes just juggling lamp positions works, but usually it’s a bugger ferreting out what’s wrong. It’s easy to suspect the controllers, but sometimes just replacing just the right lamp with a spare does the trick. But because there are 4 wires instead of just 2, I have a devil of a time finding the faulty lamp; my yellow LED Xmas gun isn’t useful on controlled 4 pin lamp sets.

Since there only 2 spare lamps in holders with each set (and some sets had no spares), I’d like to get spare 4-pin bulbs. If I just replace lamps one at a time until a set works, since they fail in straight groups of 3, that may be easiest. The pins are too long and often need trimming a bit to fit the holder or they jam going into the sockets. Problem is I’m not sure which lamp to order. Maybe you can assist. The tag on each cord says to replace with 3v fuses, and 4v. 0.25 w lamps. That’s it. In searching online I see options on Amazon (Chanzon), but they are clear lenses and mine are diffused. The ones at Amazon say 3v. More concerning is they come either common anode or common cathode, and I don’t know how to tell which that mine are. They are domed 5mm. I looked at Mouser.com but was still left with uncertainty.

Can you advise? I’d sure like to clear these 7 or 8 sets off my garage workbench, and for once have room for other projects as they come up!

Thanks,

Joel

Clackamas, Oregon

fmilburn · Answer

Hi Joel,

it is difficult to answer your question with the information provided. By the way, you need only post it once. Posting a photo of the lamps could be helpful.

I Suggest starting with some simple tests. The lamps should light at 3V. So using a 3V power source, or two 1.5V batteries in series, apply negative and positive to the various leads of a lamp until you find what lights them. To be safe put a 300 ohm resistor in series to limit current if you don’t have a current limiting power supply or you might burn the bulb out. If it only lights with the negative on one lead it is common cathode. If it only lights with the positive on one lead it is common anode. This can also be used to tell you where the RGB leads are. Now measure the spacing between the leads (pitch) on the lamps. With this information and the diameter of the lamps you have a good chance of ordering the correct replacements. Diffused lens are available from suppliers like Newark / Farnell.

ralphjy · Answer

I think that this tutorial should help you. It explains the pinout and different methods of controlling the colors.

https://www.circuitbread.com/tutorials/how-rgb-leds-work-and-how-to-control-color

Ralph

fmilburn · Answer

The video that Ralph linked appears to go into more depth and will provide useful information. The language on the tag is confusing. The LEDs don't really work at 4V or for that matter 3V. Depending on the color and way they were manufactured, they will start to conduct at different voltages called the forward voltage. For example, the red LED inside the case will probably start to conduct and thus light up around 1.6V. The voltage drop across the LED will remain fairly constant once it is at the forward voltage. The green maybe lights at 2V and the blue maybe at 2.5V depending on how they were made. The LEDs will probably fail quickly if the current is more than 20 mA for very long which is why I suggested putting a resistor in line. The controller on your LED strings probably has a constant current source to keep the LEDs from burning out too quickly.

Below is a photo of a LED I have at hand along with a 2032 button cell battery which puts out a voltage of around 3.2 V. The battery has internal resistance so it can't put out enough current to damage the LED.

The current will only flow in one direction and the LED will block in the other direction. On my LED the long leg is the cathode, or negative. If I place the positive side of the battery between the other legs and the long leg / cathode the LED lights up. For example, the leg to the far right lights the red LED when the negative side of the battery is pressed against the long leg.

And the leg just to the left of the cathode / long leg lights the green LED.

The last leg on the far left will be the blue. Notice that I always have to press the negative side of the battery against the long leg or cathode of the LED. That is why it is called a common cathode LED - the cathode is common to all colors. Some LEDs are made with a common anode where current flows in via a common leg but the cathodes are separate and thus control is done by switching on the ground side. So, it is important to determine which type you have and always place the LED into the socket in the correct orientation or it won't light up.

I am going to guess you have 5mm common cathode with 0.1 inch pitch which is what I have seen the most but check. Frosted or non-frosted will work with perhaps a somewhat different look due to brightness. Let us know if you have more questions.

ralphjy · Answer

I took another look at Joel’s picture - the controller is a TY-16F which I think means that these are “smart” LEDs not common cathode or anode types. Take a look at the APA-106

jw0752 · Answer

Hi Frank, It looks to me like it is a case of a bad LED. I had trouble once when I set my power supply to 10 mA and had my Voltage set to about 10 volts. When I hooked up the LED the current limit didn't respond quick enough to protect the LED. You wisely set your current and then slowly raised the voltage. I have also seen LEDs that partially burn out. They will still light but weakly and draw too much current. Good luck on figuring out what is going on. John

fmilburn · Answer

Here is what I know now.... I hooked up an Arduino Uno using 5V as power and the Adafruit Neopixel library. I tested it on a known good WS2812 to make sure it worked. The APA-106 is supposed to use the same protocol as the WS2812. Then I hooked up one of Joel's LEDs using the pinout of the APA-106. It wasn't lit so I jiggled it around with my finger and lo and behold it lit extremely brightly. When I pulled my finger away it turned off. So I put my finger back on and held it a second or two but it started smoking. Obviously there was no current limiting / PWM. One down, one more to go :-). I stuck the other one in and it didn't light. So I jiggled it with my finger and it lit. I immediately pulled my finger away and it turned off. Put it back on and it lit, immediately pulled away. I entertained myself that way a couple more times and stopped while it was still working. Next time I will put a resistor in series. I could have it wrong but I have double checked the wiring and believe it to be correct for an APA-106. I am going to put it aside for the evening and think about it some more.

hafcanadian · Answer

I placed the question more than once and on separate boards because I got no reply the first time some days ago, and this time there was no confirmation it went when I hit the submit button.

Thanks Frank. I assume because three of the lamp leads are the same polarity and are RG & B. I can clip the second power supply lead to any of them? I am confused about the word “common”... does it refer to the 3 that have a common charge, or the single lead that I’m measuring that is the only one with that charge? In a 2-lead LED lamp the short lead is the cathode (negative) and is on the flattened rim side of the lens. But sales images online of 4-lead ones show the second lead in from the flat side to be the longest, and it has one charge; the other 3 leads share the opposite charge.

My power supply is 0-30v and 0-10 amps. But I don’t know if I can fine tune it down to .0625a or .083a. I previously mentioned that the UL tag on each set said, “replace with 4v .024 watt spare lamps”. .024w/4v=.0625a. .024w/3v=.083a. The lamps I see on Amazon are around 3v I think, but not frosted. I will look further at element14/Newmark.

Sorry for my naïveté, but I just thought I had standard LED lamps figured out, and along come 4-leaded ones.

The photos of my lamps don’t show a long lead because the mfr. clips them off to fit their lampholders. But I’m assuming the long lead will be the second one in from the flattened lens rim side.

Joel

fmilburn · Answer

I am going to speculate a bit here. The LEDs have the following characteristics: They don't behave like a traditional "dumb" RGB LED They have the same length leads as an APA-106 and the same flat edge on the side From my testing the GND pin and VDD seem to be the same as an APA-106 Adafruit sell something similar that is said to work with their NeoPixel library The Adafruit NeoPixel library for the WS2812 doesn't quite work with these LEDs I remember reading about a change to the WS2812 and found this May 2017 post which references WorldSemi: Heads up – WS2812B NeoPixels are about to change! – Particle Blog. In the 2017 article they state that: According to WorldSemi, the new WS2812B NeoPixels have a longer required reset interval, up to 280us from 50us. They go on to say that their product would not light the WS2812Bs as a result. What may be happening is that Joel's LEDs use the old reset interval of 50 us and the NeoPixel library uses the newer interval. When I hold my finger just so (it doesn't always work) I may be changing the capacitance or something that changes the reset duration and allows it to turn on but they still don't function properly. I have the Arduino in a loop sending a new signal each pass and it turns off when I pull my finger away. Some years ago I wrote a driver for the WS2812 and a MSP430 microcontroller. I suppose I could dig out that code and modify it as necessary to change the reset period and test a lamp or we could use a logic analyzer or oscilloscope to determine what the reset period coming out of the TY-16F is and whether it matches the APA-106 protocol. But I am not sure how much good that would do if the older lamps are obsolete and can't be found. Assuming these are old APA-106 with a shorter reset duration I am running out of ideas other than ordering some new APA-106 and seeing if they work with the controller. Small quantities are available on Tindie and probably elsewhere.

hafcanadian · Answer

Toyo/Roundtripping offered 15-20 lamps at first, but ultimately put together 50 at no charge. They shipped from China through Hong Kong and arrived yesterday. They were good enough to airfreight them DHL. The only delays were through several stages of customs holds. They did have some confusion over my address, somehow getting my house number confused with the zip code; fortunately my contact there was aware enough to catch it was destined to Indiana or Massachusetts or somewhere, not Oregon. Postal address configurations in China are apparently much different than in the U.S. Along with the good faith offer was a note that if a set has lamps go out I should go buy a replacement set rather than try to replace the lamps, and that these sets are meant to last only 7-8 years at best, maybe only 2 if left outside very long - that they are sensitive to ravages of weather and handling. My sets are on the house usually about 6 weeks, Thanksgiving to a week or two after New Years, whenever my Grandson can get over to put them up and take them down off the roof ridges that my disabilities prevent me from accessing. I do the gutters and fascia reachable by ladder. The lights I already have should be adequate for many years yet, but I still want to maximize that by addressing faults in sets where I can. It hadn't dawned on me that a specific patent was involved, such that the LED bulbs are not attainable except through one manufacturer, especially one like Toyo that's big enough to effectively dominate the holiday lighting industry, a monopoly of sorts. But it's been over 7 years, so the patent would be expired; maybe it's different in China. It would still be good to know the lamp's specifics, but tracking the patent may involve more aggressive research than its worth. I'd like to take this opportunity to thank Sean, Ralph, Doug, John, and most especially Frank for your input and attempts to help me solve my problem. I regret that I could've saved Frank's time had I earlier endeavored to contact the manufacturer through the retailer's buyer system, as I ultimately did when Frank came to an impasse. Seven years ago that was the only way to get a response out of Toyo. And they didn't respond this time either until the buyers got involved... money talks with large companies. That all said, I cannot disregard all that I learned about these LEDs in the process. That's due to the commentary each of you threw into the mix... it was all very enlightening. And very, very much appreciated! Joel Photo doesn't do the "in motion show" aspect justice, as the lights move and change colors in synch There are 20 sets of 12 lamps each. You can see if one lamp gets finicky, a group of 4 usually goes all white, which screws up the "show". If it's up on the Ridgeline I have to wait for my Grandson to get away from his National Guard duties to come switch out the set with a new one. Then the faulty set sits on my workbench until the Holidays allow time to juggle lamps or try to sort out what's wrong. Sometimes I've gotten lucky and replacing one lamp does it (if I can find the right one), switching bulbs around works on occasion, or I have to replace all 12 lamps when only 4 of them light at all, and usually 3 of a group of 4 with another one by itself much further down the string. Weird. And frustrating. Toyo would just as soon I go buy another set, of course. Hopefully that won't be necessary anytime soon.

fmilburn · Answer

Assuming the lamps are APA-106, then the TY-16F is a controller that sends signals to the individual lamps. It would not have a resistor because the microcontroller in the individual lamps will use pulse width modulation (PWM) to turn the lamps on and off quickly so that the averaged current appears to dim the LEDs to our eyes (we don't see the flicker) and also keeps them from burning out. It is useful to know that the LEDs in your possession have two long and two short pins like the APA-106.

fmilburn · Answer

jw0752 dougw ralphjy I am hoping you might be able to help with this... I had Joel send me two of his RGB LEDs described above and I attached them to my bench power supply assuming the long lead was cathode. I set the maximum current to 3 mA and then increased the voltage to the red lead. On the first LED I got a dim red response at about 2.4V and then the LED went out. The green and blue did not light at all but I could get current across them. Thinking it was a bad LED I hooked up the second one. This time I got a brighter response and took a photograph. See the image below... The LED on the right is the one from Joel. The one on the left is a fresh one that was in my box of LEDs. You can see my LED is much brighter than the one from Joel at the same current and it turns on at a lower Vf. I couldn't get the green or blue on the second LED from Joel to turn on (mine worked as expected). Then I tried the red on Joel's again and now it won't light. I guess I fried it at 3 mA. So I don't have an idea of what is happening. It appears the long lead is cathode and red is in the same location as my LED. Joel sent me LEDs that were working in his string but they appeared to burn out at only 3 mA in my test. Any ideas? I was thinking I might send him some of mine that he could try in his string. Thanks for any help Frank

dougw · Answer

I don't think any LED will burn out with just 3 mA, either forward or reverse current. Presumably your power supply or a DVM will tell you if the device is common cathode or common anode. I tried several LEDs limited at 3 mA forward and reverse with a 25 V supply. Two of them did not conduct in reverse even at 25 V, the other acted like a 21 V zener. They all survived fine - they only light up when forward biased. 2.5 V is very high for a red LED. If you short the LED leads out to prove your power cables are good, then the issue would appear to be with the LED. Some LEDs may not emit much light at 3mA, try 20 mA. I have "seen" old LEDs (old technology) that don't emit visible light at 3 mA.

hafcanadian · Answer

The buyers at the seller’s main offices finally got a response from the vendor of the light sets. They passed the job through 4 of them before one got it done, but got back to me in less than a day. It would seem the company, I believe Toyo or their associated entity Roundtripping, have a patent on the lamp such that only they can supply it - it isn’t available in the US market. That’s why Frank couldn’t identify it with his tests. They told the buyer they would “make up” 15 or 20” lamps for me. When the vendor contacts me I will try to buy more than that, as I was hoping to get a package of 50 or 100, which is commonly available in other similar models, and because sometimes a set must have all 12 lamps replaced to work. With 40+ sets, I need some good backup into future seasons.

colporteur · Answer

Are the LED's common cathode or common anode type.

If you look through the side of the diode, the cup is always the cathode. You might be able to figure out what common they are by the physical construction.

fmilburn · Answer

They may have resistors installed to work at 4 V or some other scheme I haven’t seen. If you can spare some LEDs then just slowly turn up your power supply and see what happen. They should light up briefly even if you toast them and you can determine the equivalent forward voltage and whether they are common anode or cathode. Else you can put current limiting resistors (edit: or a potentiometer so that you can ramp up current) in series as suggested earlier. If all else fails let me know and I will give you my address by private message so you can send one to me and I will test it.

LED 4-Pin help needed

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