Help identifying an LED and also an application question - Page 1
Forum section: electronics / beginners

author: TT_Vert
author_rank: Regular Contributor
timestamp: January 25, 2019, 03:19:00 pm
content: I have a car mirror which has a yellow color temperature which I want to replace w/ a white LED. I've disassembled the mirror and found the LED to be a type I've never seen. It looks like a transistor that has the hole in it to mount to a heatsink. My first question is, the way they designed it is using two different colors. The center leg is ground the left leg is blue and the right leg is orange. They are both illuminated together to make this yellow color. My questions is why would they do this? I checked the forward voltage and the amber draws 20mA at 2V and the blue 20mA at 3.3V. My second question is, what is the name of this LED form factor? Third is, can I just get away w/ a 5000K LED In this form factor and modify resistors as required to get correct current limiting? The way this is designed I really need to stick w/ the existing form factor. I looked on mouser and I cannot seem to find anything like this and nothing in amber/blue.I included a quick drawing I did. The top hole is the mounting hole.Thanks guysDave

author: rrinker
author_rank: Super Contributor
timestamp: January 25, 2019, 04:37:48 pm
content: I would suspect that it does more than just light up with that one color. Different conditions or settings would probably activate just the blue or just the orange. Possibly options you don;t have in the car this came from, but are available, or maybe something that isn't frequently encountered. I can't imagine they would ever use a dual color LED just to make other other color that is readily available as a simple LED.Frankly - if this is on the side facing the driver, I would NEVER use a white LED, it's distracting and more harmful to night vision than other colors.

author: Zero999
author_rank: Super Contributor
timestamp: January 25, 2019, 05:14:19 pm
content: It probably adjusts its colour, depending on the ambient lighting conditions.Why do you want to change it?

author: Domagoj T
author_rank: Frequent Contributor
timestamp: January 25, 2019, 05:29:33 pm
content: Is this what you're looking for?http://www.farnell.com/datasheets/526930.pdf

author: TT_Vert
author_rank: Regular Contributor
timestamp: January 25, 2019, 05:37:29 pm
content: Thanks guys. To clarify this is an aftermarket mirror by gentex for my convertible. The LEDS illuminate when door is opened and also when i turn on the lights w/ the switch (Always the same warm white). I want to go to a more white cool white LED as I do not like the warm white color temp and all the other LEDS (footwell, etc) are a cool white (around 5000K). There is no other functionality with these lights and the way this is designed it is only downward facing light in chrome light direction bezels so they cannot be used to illuminate buttons, etc. That's sort of why I am confused as to the reason they'd use both colors to make one color. It could be that given this mirror design is probably over 10 years old he technology just wasn't there?@Domagoj T htat is the correct form factor (maybe a bit smaller but close) but only a 2 leg whereas the OE is a 3 leg. I suppose I could squish the legs together a bit to make that work if need be.Dave

author: Domagoj T
author_rank: Frequent Contributor
timestamp: January 25, 2019, 06:09:48 pm
content: The original has three legs so it can power two different colors (one leg for each LED + one common). Since you want white, there are only two legs. Alternatively, you can look for RGB, but that one will have four legs.You could play with your existing one and reduce the current to the orange LED. That will lead to the blue one being more prominent and shifting the overall color more towards the cooler side of the spectrum, at the cost of lower total brightness.

author: TT_Vert
author_rank: Regular Contributor
timestamp: January 25, 2019, 07:04:33 pm
content: Yeah I need all the brightness I can get so i think these you linked me to will work as I don't need two colors to make what i want. With that said I can't seem to source what you linked me to. Mouser doesn't have any TO220 LED stuff nor does anyone else it seems.Dave

author: Domagoj T
author_rank: Frequent Contributor
timestamp: January 25, 2019, 07:37:04 pm
content: Try going straight to the source:http://www.omc-uk.com/components/led-lamps-displays/high-power-leds

author: TT_Vert
author_rank: Regular Contributor
timestamp: January 25, 2019, 07:50:06 pm
content: Thank, I've done that but given they are in UK and I'm in the US it may be cost prohibitive. I may have to get creative w/ another LED type.Dave

author: Domagoj T
author_rank: Frequent Contributor
timestamp: January 25, 2019, 08:03:19 pm
content: Maybe they can point you to a US distributor or just feel sorry and send you a couple of LEDs, who knows.I had surprisingly good experience with Herpa (the model making company). While moving, I lost one engine of the 747 and they shipped me the replacement at no cost to me.

author: TT_Vert
author_rank: Regular Contributor
timestamp: January 25, 2019, 09:20:34 pm
content: The 747 will fly on 2 engines so you were still good. Now if you lost an engine in a P51 you'd be in for a ride.With that said, I did ask just that and told them I wasn't looking to buy in bulk. For the time being I used White T1 LEDS. It works fine but I'm going to wait until tonight to see if they'll be bright enough. Not the best way to do it but you can't really see this as it's recessed in the mirror. if someone has a source for BRIGHT cool white LEDS that are 1W or less I'd be interested. Or other possible solutions one w/ more experience has than myself. Sorry for the angle as it makes the LEDS not look center (they are), I didn't want to open the door and floor the camera w/ light.

author: Brumby
author_rank: Unknown
timestamp: January 25, 2019, 09:34:25 pm
content: Quote from: TT_Vert on January 25, 2019, 09:20:34 pm I believe anempty747 can fly and land on only 1 engine Interesting package. I can't say I've ever seen that before ... but then I don't get out much.

author: TT_Vert
author_rank: Regular Contributor
timestamp: January 25, 2019, 10:50:51 pm
content: From what I've read you cannot maintain altitude on one engine in a 747. It can help w/ the glide slope thoughSo can anyone recommend a fairly bright light hat would fit my needs here? I have confirmed the T1 does actually illuminate well but I'd like a hair brighter if possible. Even something that isn't so long so i can use more of the reflector to help w/ lighting. Maybe even round LEDS on a PCB w/ a metal round plate w/ wires to main pcb would work.

author: TT_Vert
author_rank: Regular Contributor
timestamp: January 25, 2019, 11:04:17 pm
content: Just came up w/ a much better solution. Using some 1W 6500K replacement lights for my aquarium lighting I just reamed the holes a bit and did this. I'll use jumper wires from the pcb to these. These are much brighter also. Question, anyone know of an adhesive that is resistant enough to the head of these LEDS but is removable? I was almost thinking of using a dab or two of RTV. I have used it on turbo manifolds in lieu of gaskets so I know it's up to the task as far as heat goes.Perhaps one of you can answer something about these LEDS I may potentially use. The specs are as follows "QuoteMy question is that is says the forward voltage is between 3.4-3.6V but the current is 350mA. Isn't that extremely high for a white LED? Don't they usually draw around 20mA? Is this spec assuming some type of heat dissipation or the voltage it can support w/o active cooling? As of now I have the light powered at 2.70V and the back metal part of it is at 93deg F. I then increased it to 3.3V and 170mA were being drawn stabilizing at 151 deg. F. I just don't know what an acceptable temp is w/o any active cooling. Plus is's going to be in a plastic housing so I don't want to melt that. Not sure at what temp that plastic melts however.ThanksDave

author: alsetalokin4017
author_rank: Super Contributor
timestamp: January 26, 2019, 02:48:46 am
content: Well, those are "One Watt" rated LEDs, right? So how do you get to one watt, if you only draw 20 mA? Answer: You don't. You give them enough voltage so that they draw about 350 mA and that's probably going to be 3.5 volts or so.Those LEDs are designed to be mounted on a heatsink, or at least a PCB with sufficient copper area to carry away the heat when they are fully powered at 350 mA.Of course you can power them at lesser brightness with lesser current and have less heat to get rid of (as you have found out by giving them only 2.7V). But that's inefficient.

author: TT_Vert
author_rank: Regular Contributor
timestamp: January 27, 2019, 12:23:47 am
content: Thanks, given the mirror is in many pieces/boards and to get it apart to measure voltage while still assembled it would have been difficult to measure the actual voltage while emulationg door open so I don't know what the input voltage was. Given it has 38 ohm resistors for each of the 3.3V@20mA LED I'd have to assume it's under 5V but I don't know for sure. I did keep the light powered on w/ 3.3V (which is about what the led that was on that circuit was probably getting) and it didn't get over 151 degrees while on for about 20 minutes so hopefully for this application it won't get near that hot. What do you guys think of that thinking?Dave