Author Topic: I have an SMD LED which is 3mmx2.7mm which I cannot find, can you help?  (Read 5318 times)

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Offline TT_VertTopic starter

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It it parts the item below.  The forward voltage is 3V with a 20mA current draw and is powered by a 12V source.  There are 48 of these on this board.  I looked on digikey, mouser, etc.  Seems these do not exist.  Are these actually 3030s ?  I measured about 10 times thinking I was going nuts.

Dave



 

Offline Brumby

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Re: I have an SMD LED which is 3mmx2.7mm which I cannot find, can you help?
« Reply #1 on: February 24, 2018, 06:08:00 am »
Possibly 3528's

I found a datasheet where the white body is 3.2mm long x 2.8mm wide, but with the terminals included, it's 3.5mm long x 2.8mm wide.

If you only measured the white body to get your dimensions, then this puts you out by 0.2mm x 0.1mm.
 

Offline Brumby

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Re: I have an SMD LED which is 3mmx2.7mm which I cannot find, can you help?
« Reply #2 on: February 24, 2018, 06:12:39 am »
Make that 2835's.  They have the rectangular emitter area.

I've also found drawings with the external dimensions of two different data sheets, both for "2835 SMD LEDs":

One has: 2.74mm x 3.4mm
The other: 2.8mm x 3.5mm
« Last Edit: February 24, 2018, 06:21:54 am by Brumby »
 

Offline TT_VertTopic starter

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Re: I have an SMD LED which is 3mmx2.7mm which I cannot find, can you help?
« Reply #3 on: February 24, 2018, 06:21:24 am »
I did measure at the body of the LED and with the terminals and It's definitely a max of 3.0mm .  maybe 2.95mm w/o terminals, they don't protrude out much at all.

Dave
 

Offline Brumby

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Re: I have an SMD LED which is 3mmx2.7mm which I cannot find, can you help?
« Reply #4 on: February 24, 2018, 06:26:54 am »
I threw 2830 into Google and came up with a couple of hits on Alibaba.  One was a circular emitter and then there's this: https://hanhualed.en.alibaba.com/product/60267278940-801677488/shenzhen_led_diode_2830_snd_led_manufacturer_supplied_2835_smd_led_20_23lm.html

... but they seem to be 2835's
 

Offline TT_VertTopic starter

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Re: I have an SMD LED which is 3mmx2.7mm which I cannot find, can you help?
« Reply #5 on: February 24, 2018, 06:29:31 am »
If they were 2835s they'd be 2.8x3.5mm at some point though right? What makes you  think what i have may be the 2835s if they don't dimensionally match? 

Thanks much,

Dave
 

Offline Brumby

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Re: I have an SMD LED which is 3mmx2.7mm which I cannot find, can you help?
« Reply #6 on: February 24, 2018, 06:44:49 am »
Sorry if I wasn't clear - I meant the Alibaba ones that came up on a search for 2830 actually look like they are 2835's.

Not the ones you have.


Any idea on how thick your chips are?
 


Offline TT_VertTopic starter

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Re: I have an SMD LED which is 3mmx2.7mm which I cannot find, can you help?
« Reply #8 on: February 24, 2018, 06:58:24 am »
Yeah I also found tons of 3030s.  So is it possible these are just some one off or very hard to come by or obsolete chinese sourced LEDS?   I did buy on Ebay from a US seller a few years back and looking even now the LED is unidentified in his ad.

https://www.ebay.com/itm/10X-White-48SMD-Panel-LED-Festoon-T10-BA9S-Adapter-Interior-Dome-Map-Light-Bulb/122603838385?hash=item1c8bc21bb1:g:2z8AAOSw4HlZbGCH:sc:USPSFirstClass!60107!US!-1

Dave
 

Offline TT_VertTopic starter

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Re: I have an SMD LED which is 3mmx2.7mm which I cannot find, can you help?
« Reply #9 on: February 24, 2018, 06:59:07 am »
Sorry if I wasn't clear - I meant the Alibaba ones that came up on a search for 2830 actually look like they are 2835's.

Not the ones you have.


Any idea on how thick your chips are?

Ahh understood.  I'll check the thickness in the AM.

Dave
 

Offline Brumby

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Re: I have an SMD LED which is 3mmx2.7mm which I cannot find, can you help?
« Reply #10 on: February 24, 2018, 11:02:30 am »
So is it possible these are just some one off or very hard to come by or obsolete chinese sourced LEDS?

It could also be some LEDs that were manufacturer rejects because of their size (or other reasons as well) sold off at the Shenzhen markets.
« Last Edit: February 24, 2018, 11:05:26 am by Brumby »
 

Offline Kjelt

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Re: I have an SMD LED which is 3mmx2.7mm which I cannot find, can you help?
« Reply #11 on: February 24, 2018, 03:15:31 pm »
It could also be some LEDs that were manufacturer rejects because of their size (or other reasons as well) sold off at the Shenzhen markets.
That would be very unlikely IMO, the plastick and metal base carriers are not made by the the led manufacturers themselves the same as that the ic housings are not made by semicon fabs. So on the intake these would have been rejected since in a 3030 manufacturing process it would cause a lot of problems.

My guess this is a niche product from one of the many chinese led manufacturers. Those small factories with their product range arre not so known in the rest of the world. I have some reels with leds where only chinese for me unreadable datasheet and catalogs exist. Some series are not even publicly for sale but are specially made on a mass contract for instance for some lighting manufacturer wanting to produce a series of a few million led lamps for the chinese or other market.
 

Offline TT_VertTopic starter

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Re: I have an SMD LED which is 3mmx2.7mm which I cannot find, can you help?
« Reply #12 on: February 24, 2018, 06:16:49 pm »
Well that is good enough for me.  I was trying to modify these lights I had to convert from 12 to 24V but it seems like more headache that it's worth.  I could probably make the 3030s work but it's just not worth it.

Thanks for the insight guys, these little things really do confuse a newbie!  I feel like I'm missing something and don't know what I don't know..
Dave
 

Offline Kjelt

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Re: I have an SMD LED which is 3mmx2.7mm which I cannot find, can you help?
« Reply #13 on: February 24, 2018, 06:45:39 pm »
Well that is good enough for me.  I was trying to modify these lights I had to convert from 12 to 24V but it seems like more headache that it's worth.  I could probably make the 3030s work but it's just not worth it.

Thanks for the insight guys, these little things really do confuse a newbie!  I feel like I'm missing something and don't know what I don't know..
Dave
What is the layout of the led string? If it is 12V they probably have only three leds or four in series and then many of these parallel. Are there resistors in the string? In theory you need to go from 4S12P to a 8S6P construction. Could be as easy as opening a pcb trace with a scalpel, cleaning the copper and soldering a few thin teflon wires.

Other perhaps better solution: place a high efficiency dc-dc converter in front.
 

Offline TT_VertTopic starter

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Re: I have an SMD LED which is 3mmx2.7mm which I cannot find, can you help?
« Reply #14 on: February 24, 2018, 06:56:44 pm »
I will have to double check but it's a PCB w/ 6 rows of 8 LEDS.  I am also trying to better understand how it is currently wired.  There is one 8.25 ohm resistor on the positive side and one on the negative side.    I was hoping to cut it in half and wire the two in parallel to make it 24V.  I did this and got it to work on 24V doing this but it is getting very warm and I think drawing too much current.  But i really don't know what i'm doing other than just experimenting :)  If you are interested in adding input I could get you the drawing I made of how I think it's wired.  I could also tell you the current draw as it is in my config but every LED resistor parallel/series calculator I see does not show a recommended method as it is now even in its current configuration of two 8.25ohm resistors so I'm confused there as well.

Dave
« Last Edit: February 24, 2018, 08:07:50 pm by TT_Vert »
 

Offline drussell

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Re: I have an SMD LED which is 3mmx2.7mm which I cannot find, can you help?
« Reply #15 on: February 24, 2018, 09:20:35 pm »
I was hoping to cut it in half and wire the two in parallel to make it 24V.

That would make it 6V.

Why don't you just change the resistors or add some other kind of current regulator?
 

Offline TT_VertTopic starter

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Re: I have an SMD LED which is 3mmx2.7mm which I cannot find, can you help?
« Reply #16 on: February 24, 2018, 09:33:10 pm »
I'm sorry I meant I wired the two in series to make it 24V.

It's lighting up a 3d printer and this PCB is on a custom bracket on the printhead (Extruder) and I don't have a bunch of space.  I could add some type of current regulator but it'd have to be near the power supply.  I did play w/ resistors but I'm still learning and not exactly sure what I'm doing but they were getting hot so I was clearly doing something wrong.  I've been going through calculators and trying to understand what I"m doing and why it's having the effect it is but it's taking me some time.  I am more of a hands on learner and really learn by doing and noting results to be honest.  I did check the PCB again and this what I came up with (See attached pic).   It's an 8x6 array of LEDS, the left 16 (left 2 rows) share the same ground and the right 16 share (right two rows) the same hot.  THen the middle 16 are in series.  Would this be a 3P?  This is what I think it is but I'm not even remotely confident in that answer.  Or perhaps S3P3 or 1S2P?  The current draw @12Vdc is 130mA and forward voltage @12Vdc is 3.08V. 

I'm also trying to find out how/why the 8.25ohm resistors work in this circuit, it just doesn't make sense to me.

Thanks again,

Dave
« Last Edit: February 24, 2018, 09:40:26 pm by TT_Vert »
 

Offline Kjelt

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Re: I have an SMD LED which is 3mmx2.7mm which I cannot find, can you help?
« Reply #17 on: February 25, 2018, 12:32:02 am »
It does not make much sense to me either.
Most white leds are slightly more than 3V, around 3,2-3.3V depending on the current.
If you have exactly 12VDC the string length will usually be 3 leds since 4 can be too much, certainly over time as the voltage slightly increases.
So that would make the PCB consist of 16 paralel strings of three leds in series.
Since you say there are only two resistors instead of 16 my guess is that each 8 paralel strings get one resistor.
So this would make it two times a 3S8P configuration. can you verify this?
« Last Edit: February 25, 2018, 09:08:48 am by Kjelt »
 

Offline Brumby

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Re: I have an SMD LED which is 3mmx2.7mm which I cannot find, can you help?
« Reply #18 on: February 25, 2018, 01:00:18 am »
Following the PCB as best I can, I make it 2P-3S-8P ... like this:



(Sorry for the rough line work ... I'm not too crash hot drawing with a mouse.)

If so, then I think your connections are on the wrong side of the resistors ... but I can't see that clearly enough to be certain.  The resistors will be for current limiting.
« Last Edit: February 25, 2018, 01:08:44 am by Brumby »
 

Offline Brumby

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Re: I have an SMD LED which is 3mmx2.7mm which I cannot find, can you help?
« Reply #19 on: February 25, 2018, 01:14:05 am »
With so much parallel connection of the LEDs, the risk of uneven current distribution due to variances in each LED is significant.  However, these variations tend to be much less when all the LEDs come from the same manufacturing run ... and that is how a lot of these cheap arrays can get away with it.
 

Offline TT_VertTopic starter

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Re: I have an SMD LED which is 3mmx2.7mm which I cannot find, can you help?
« Reply #20 on: February 25, 2018, 01:20:01 am »
Yes Brumby, you are correct with your drawing.  The connections are correct as i have another unmodified one which works fine. Care to explain how you get to the 2P3S8P?
 

Offline Brumby

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Re: I have an SMD LED which is 3mmx2.7mm which I cannot find, can you help?
« Reply #21 on: February 25, 2018, 01:32:46 am »
Each row of 6 is as follows:
LED 1 and 2 are in parallel - 2P  Call this group A
LED 3 and 4 are in parallel - 2P  Call this group B
LED 5 and 6 are in parallel - 2P  Call this group C

Groups A, B and C are in series - 3S .... so each row is 2P 3S

You then have 8 rows in parallel - so 2P 3S 8P
 

Offline Brumby

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Re: I have an SMD LED which is 3mmx2.7mm which I cannot find, can you help?
« Reply #22 on: February 25, 2018, 01:36:23 am »
Do your power wires go directly to the LED rails down each side - or do they go through the resistors?
 

Offline TT_VertTopic starter

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Re: I have an SMD LED which is 3mmx2.7mm which I cannot find, can you help?
« Reply #23 on: February 25, 2018, 01:38:42 am »
I will absorb this in a bit but answer your question the hot and ground go through resistor first
 

Offline Brumby

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Re: I have an SMD LED which is 3mmx2.7mm which I cannot find, can you help?
« Reply #24 on: February 25, 2018, 02:10:11 am »
That's good.  They should.
 


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