12V LED and drivers

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bob_ninja
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12V LED and drivers

I am trying to build a simple lamp using 3×18650 power source.
I want to use this LED:
12V LED

I am looking at 2 power levels, high at 1A and lower one around 0.1A-0.3A
I found these:
10W driver

Which is specified for 12V 1A producing about 10W.
Now I assume its input and output are both 12V right? And it draws about 1A to supply to the LED.

The lower mode driver is:
1W driver

This is where I got confused. Title says 1W so expect 1 / 12 = about 0.1A
Instead specification is 0.33A

So why is current looking odd and is output voltage still 12V?

Can someone clear up?
thanks

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mattthemuppet
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the drivers that you’re looking at are for 12V desktop light bulbs that typically have a single LED. So they buck the voltage down from 12V to 3.5V or so. The 1W driver should then supply ~330-350mA, which fits.

Either way, if you want to drive a 12V LED from a 3S pack you can’t use a buck driver (Vin > Vf) and might not be able to use a boost driver with a 11.1V pack.

What’s the application? There might be easier ways to skin the cat you have in mind Smile

texaspyro
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Those drivers are buck mode drivers. Their ouput voltage must be less than the input voltage minus a couple of volts. That LED is a 3×3 array of LEDs. It needs around 10V to drive it to full power. A 4×18650 pack should work well with those drivers.

bob_ninja
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Ok I find the specs confusing:

CURRENT DRAW 330 mA
INPUT TYPE 12V
POWER CONSUMPTION 1 W

So input is 12V but what is missing in description is output is about 3.5V which is typical for LEDs, hence 3.5 * 0.33 is about 1W

Then I am guessing this LED I found is actually 3 LED elements in series that need about 12V, something like that. Got it. Then I am not sure how to drive it if all drivers output 3.5V

I am making a portable light for general room lighting, so don’t need a reflector.
Since a 3s pack produces about 12V I thought using a 12V input LED would be the best match.
So I simply need a driver to regulate the current, 2 levels around 1A and another lower around 0.1A-0.3A

Or am I looking for some other device to regulate current? Or different driver type that outputs 12V?

Another possibility is simply use 3 separate normal LEDs with individual drivers. I have a 4 way switch so I can simply wire them in series; in each switch position bring additional LED into circuit in series. Something like that. Is that the reason why some drivers have AxB spec, like this:

3×1W driver

Does this mean output for 3 LEDs in series, 1W for each (330 mA)?

thanks

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bob_ninja
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texaspyro wrote:
Those drivers are buck mode drivers. Their ouput voltage must be less than the input voltage minus a couple of volts. That LED is a 3×3 array of LEDs. It needs around 10V to drive it to full power. A 4×18650 pack should work well with those drivers.

Well 3S pack would produce around 12V. Why 4 cells?

I am just concerned that LEDs may pull more than 1A without regulation and would overheat.
Right?

Ohhh, you mean I need 4 cells so then I can use a buck driver to bring down voltage to 12V as rated.

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bob_ninja
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How does a particular driver know that it is powering a single LED and needs to output 3.5V or 3 LEDs in series that require around 11V?

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texaspyro
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Those are constant current drivers. They will output whatever voltage is needed to cause 350 mA or 1A to flow into the LED. They can output voltages up to the input voltage minus around 2 volts. Thos particular drivers have a bridge rectifier and filter cap on the input. You can drive them with either AC or DC. That 10W one is good to about 30V in.

A 3S pack could output 9V if it is near empty. You need 4S to have enough headroom to drive the array.

bob_ninja
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So my choice of LED and drivers works fine, just need a 4S pack.
18650s will drive it nicely.

Great explanation, thanks Smile

And sorry for newb questions.

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Shadowww
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Why don’t you just use normal ~3V LED and high efficiency buck driver? :S

bob_ninja
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Shadowww wrote:
Why don’t you just use normal ~3V LED and high efficiency buck driver? :S

Because I am trying to use about 10W, 1A from 3 or 4 18650 cells.
Maybe the latest XML could handle it but it would be pushing it too hard, no?

I have a 3 x XML light using 2 18650 cells at 2A and 4A modes. My cells are recycled from laptop packs, so 1A is probably much more realistic. Better ones can handle 2A but wouldn’t last.

I suppose I could push 1A for about 4W max into a single XML or something like that.
Hmmmm, maybe that is the way to go. Simpler.
I will have to check what is the max power rating for XML. I though I read some place it is 1A-2A range.

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Shadowww
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Why not to use 6V MT-G2 then? It can handle as much as 18W of power, and still it’s voltage is low enough to easily drive it from 3 cells.

Max. power range for XM-L is 3A, btw (10W).

bob_ninja
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Shadowww wrote:
Why not to use 6V MT-G2 then? It can handle as much as 18W of power, and still it’s voltage is low enough to easily drive it from 3 cells.

Max. power range for XM-L is 3A, btw (10W).

I am having a hard time finding MT-G2. Also I am trying to keep it a low budget little experiment.
I can find XML T6 on usual sites like dx and ft, etc.

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Shadowww
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Well, then just use XM-L, it won’t have a problem with 10W (as long as you cool it down properly!)

bob_ninja
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So if I downgrade to less power then best combo would be:

XML T6

buck drivers:

high level ?W

(page says 10W 1A, but single XML at 1A and 3.5V would be 3.5W)

low level 1W mode

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bob_ninja
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Shadowww wrote:
Well, then just use XM-L, it won’t have a problem with 10W (as long as you cool it down properly!)

Certainly since it is a desk lamp, size is not a problem. I am going to attach some PC type passive heat sinks.

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dthrckt
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I’ve tried a couple 12V/10W emitters, similar to what you linked, but from DX.

IMO, the only reason to use them instead of Cree emitters (since they offer emitters with 3.x, 6, 9, 12, an even higher Vf) is because they’re very floody

sometimes that’s useful, particularly in an area type light, like say lighting a yard, dock, or in your case, a room.

xm-l is pretty floody though, but if lumens/Watt is more important than a very floody beam profile, go with xm-l, since they’re a bit more efficient.

using a single 12V emitter could simplify the project, if you figure out the right driver

here’s a good reference for finding them. it isn’t all inclusive, but if you email Ian (he’s also a member here), he does update the info

http://www.videofoundry.co.nz/ianman/laboratory/research/driverlist.php

Shadowww
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If you’re still looking for 12V driver, take a look at this one: http://dx.com/p/t6-2500-3000ma-3-mode-regulated-led-driver-circuit-board...

Cheap & suits all your needs Smile

dthrckt
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I would think 2.5 – 3A would fry that 12V/10W emitter pretty quick

Shadowww
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dthrckt wrote:
I would think 2.5 – 3A would fry that 12V/10W emitter pretty quick
I meant it for use with XM-L, not with 12V emitter
bob_ninja
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I settled on using 2 cheaper XPGs:
XPG

And 2 buck drivers for 2 modes, 1A and 0.3A:
1A

0.3A

I forgot that my switch is rated for 1A so don’t want to go to 2A and 3A levels. I can stay with 3S supply and get about the same light as from 1 XML.

Also will try one of these for cooling:

Active

Passive

Or maybe try to combine them … TBD

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dthrckt
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good luck. take pictures Smile

bob_ninja
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Shadowww wrote:
If you’re still looking for 12V driver, take a look at this one: http://dx.com/p/t6-2500-3000ma-3-mode-regulated-led-driver-circuit-board...

Cheap & suits all your needs Smile

I looked at it last night, but was confused about switched. In the comments someone suggested switches rated at 1.5A but driver is well over 2A.
I didn’t feel comfortable with higher current while my and other listed switches are rated for 1-1.5A

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Shadowww
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bob_ninja wrote:
Shadowww wrote:
If you’re still looking for 12V driver, take a look at this one: http://dx.com/p/t6-2500-3000ma-3-mode-regulated-led-driver-circuit-board...

Cheap & suits all your needs Smile

I looked at it last night, but was confused about switched. In the comments someone suggested switches rated at 1.5A but driver is well over 2A.
I didn’t feel comfortable with higher current while my and other listed switches are rated for 1-1.5A


Input current is ~1A at 12V, so if you’d switch input, not output (switching output on such driver, actually, is not recommended at all!) you’d be fine.
bob_ninja
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Thanks for all the help Smile
Here is current build. The questions are for the next build that should double light output.

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Werner
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I have the same led as mentioned in post 0.
Any datasheets available? Who is manufacturer?
I tried it and it looks very nice.

I have this driver which is 1A capable and dimmable like the other one.
http://www.fasttech.com/p/1110703
I want to mod my desk lamp

texaspyro
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A lot of those PT4115 10W drivers have 0.2 and 0.3 ohm current sense resistors in parallel. This gives around 750 mA out. You can parallel them with another 1 ohm resistor to get closer to 1 amp output. When I tried pushing one to the 1.2 amp rating of the chip, it went into thermal shutdown mode. Also, it would probably be a good idea to not let that filter cap rest on the driver chip… it gets warm.

Werner
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So what is this LED, datasheet?
http://www.fasttech.com/products/1103511