Wooden Lantern Build

MLD03c

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Aug 4, 2021
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Hey guys, I make wooden toys and other gadgets. I am wanting to make a wooden camping type lantern and am truly overwhelmed by all that goes into LED light tech. I want to make a 100-200 lumen light, warm color. So not wanting a crazy bright expensive build, just something practical with a warm color that is also safe and not prone to overheating. I have soldered on project boards etc... and run electronics/switches in other toys so I am not worried about the physical execution.

On the super simple side I'm thinking I can just use a simple 1 watt cob led like this on a pcb, 3 aaa batteries and an appropriate 1/2 watt resistor that brings things down to 350ma Or maybe this guy instead of resistor. I am thinking no heat sink needed with that low a power?

OR, should I go the extra mile with 3 watt, get these LED's, and this board with build in linear driver and run it off 3aaa. Would I need a good heat sink at that point?

Or lastly, do either of the above but incorporate a 18650 and this charge controller?

Greatly appreciate any constructive opinions or guidance.

Thanks,

Lee

I know I am new but I did at least TRY to research before asking.
 
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cadcoke5

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For one project, I purchased some cheap $1 store LED candles. The flicker LED didn't need a resistor, and just wired to the battery. I wired them in parallel. That is I tied all the positive leads together and the negative leads together.

Of course, this ignores the fact that a lantern doesn't really flicker. It seems to be impossible to get a LED lantern that has a housing that looks realistic, but doesn't flicker like it is in the middle of a hurricane while an earthquake is happening.

Another approach is to buy an LED flashlight bulb. Though, it is harder to find ones with a warm color. Automotive and RV LED bulbs are also another choice, and are often available in warm white. But they typically are only available for 12v.


-Joe
 

LEDphile

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If you're going to run a single LED at 350mA, you're going to want more of a heat sink than just a metal-core star board to keep the LED temperature to an appropriate level, although a few square inches of aluminum plate to function as a heat spreader is probably sufficient. Alternatively, you could use a larger LED array with a lower power density - for a couple hundred lumens the power density is usually low enough to not require more heat sink than the LED PCB provides.

I'd consider something like this, although the 12V input requirement may present some challenges
 

DIWdiver

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A typical lantern has a 360 degree wide beam (with probably a few shadows in it), and maybe 90 degree vertical. That's pretty difficult to simulate with a single LED, unless you have just the right reflector. I've seen it done poorly, not well.

How accurately do you want to replicate a true "lantern' style light pattern? Or is that not a concern at all?

You probably want 2-3 square inches of exposed heatsink surface per watt of heat generated in the LED and driver. I would err on the high side.

With the latest, quality LEDs, as little as 50% or even less of the electrical power fed to the LED is turned directly to heat. With poor quality LEDs this could be 80% or more. Also, cheap ones will fade much faster, though you may never run these enough to get to that.
 

MLD03c

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Aug 4, 2021
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For one project, I purchased some cheap $1 store LED candles. The flicker LED didn't need a resistor, and just wired to the battery. I wired them in parallel. That is I tied all the positive leads together and the negative leads together.

Of course, this ignores the fact that a lantern doesn't really flicker. It seems to be impossible to get a LED lantern that has a housing that looks realistic, but doesn't flicker like it is in the middle of a hurricane while an earthquake is happening.

Another approach is to buy an LED flashlight bulb. Though, it is harder to find ones with a warm color. Automotive and RV LED bulbs are also another choice, and are often available in warm white. But they typically are only available for 12v.


-Joe
Hmmm…wouldn’t it take like a gazillion of those flicker lights to hit 100 lumens lol? That’s an interesting idea regarding the rv Led lights . I’ll check out their power requirements…thanks for the response.
 

MLD03c

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If you're going to run a single LED at 350mA, you're going to want more of a heat sink than just a metal-core star board to keep the LED temperature to an appropriate level, although a few square inches of aluminum plate to function as a heat spreader is probably sufficient. Alternatively, you could use a larger LED array with a lower power density - for a couple hundred lumens the power density is usually low enough to not require more heat sink than the LED PCB provides.

I'd consider something like this, although the 12V input requirement may present some challenges
If you're going to run a single LED at 350mA, you're going to want more of a heat sink than just a metal-core star board to keep the LED temperature to an appropriate level, although a few square inches of aluminum plate to function as a heat spreader is probably sufficient. Alternatively, you could use a larger LED array with a lower power density - for a couple hundred lumens the power density is usually low enough to not require more heat sink than the LED PCB provides.

I'd consider something like this, although the 12V input requirement may present some challenges
Ok, thanks for the advice. So do you think an array of 3 LED’s could work? About 50 lumens a piece on their own circuit board star? I have purchased most of these items so I plan to experiment. I like that 3LED chip you sent. May have to try that with a voltage booster! The good thing about a lantern is that you have more space to monkey around with inside! Maybe could get away without having a heat sink? Only reason I’m questioning the heat sink is that I’ve seen plenty of cheap ~50 lumen lights without heat sinks and plastic bodies that barely get warm.
Thanks for the insight. You guys typically make your own heat sinks or do you buy them as well!
 

MLD03c

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Aug 4, 2021
Messages
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A typical lantern has a 360 degree wide beam (with probably a few shadows in it), and maybe 90 degree vertical. That's pretty difficult to simulate with a single LED, unless you have just the right reflector. I've seen it done poorly, not well.

How accurately do you want to replicate a true "lantern' style light pattern? Or is that not a concern at all?

You probably want 2-3 square inches of exposed heatsink surface per watt of heat generated in the LED and driver. I would err on the high side.

With the latest, quality LEDs, as little as 50% or even less of the electrical power fed to the LED is turned directly to heat. With poor quality LEDs this could be 80% or more. Also, cheap ones will fade much faster, though you may never run these enough to get to that.
Ok I will experiment with heat sinks and keep that in mind. Do you typically make your own or buy them?

As for the beam, I plan an casting something out of resin…something like 2/3rds of a 2 inch sphere. I will probably put some gold glitter or something similar in there for affect…at least that’s what I am picturing. So yeah it’s definitely gonna be more on the decorative side of things, but I want to make sure that it still has a real
Degree of functionality. The goal is something vaguely reminiscent of an old school Coleman lantern, but smaller, made of wood, and with the aforementioned “bulb”. Something for a mature kid, but surprises the adult that it’s actually useable.

Thanks for the advice. I’m sure it will take me a few wacks at it to get it right!
 

LEDphile

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Mar 8, 2021
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Maybe could get away without having a heat sink? Only reason I’m questioning the heat sink is that I’ve seen plenty of cheap ~50 lumen lights without heat sinks and plastic bodies that barely get warm.
Thanks for the insight. You guys typically make your own heat sinks or do you buy them as well!
The issue isn't the temperature of the outside of the unit, it's the temperature of the LED chip itself. Having a poor thermal path (e.g. due to lack of heat sink) will result in the outside of the light being cooler, even though the temperature of the LED chip is higher. There's no magic to heat sinks - their purpose is to transfer the heat from one location into the ambient environment.

As far as getting away without one in the design, it generally comes down to power density. If your power density is low, it's often possible to use the copper of the PCB as the sole heat sink for the LED and still keep the LED temperature in a reasonable range. OTOH, if the power density is high, you'll need more sophisticated thermal design to transfer the heat from the LEDs to the environment. As a rule of thumb, the point at which LED heat sinks start becoming important (vs. just using the PCB) is above 1/4W per LED with typical LED spacing (so LEDs perhaps 20mm on center).
 

turbodog

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Ok I will experiment with heat sinks and keep that in mind. Do you typically make your own or buy them?

As for the beam, I plan an casting something out of resin…something like 2/3rds of a 2 inch sphere. I will probably put some gold glitter or something similar in there for affect…at least that’s what I am picturing. So yeah it’s definitely gonna be more on the decorative side of things, but I want to make sure that it still has a real
Degree of functionality. The goal is something vaguely reminiscent of an old school Coleman lantern, but smaller, made of wood, and with the aforementioned “bulb”. Something for a mature kid, but surprises the adult that it’s actually useable.

Thanks for the advice. I’m sure it will take me a few wacks at it to get it right!
be sure to throw up a pic of the finished item
 

alpg88

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Apr 19, 2005
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up to 700ma, you can get away with a large chunk of aluminum or copper inside a sealed plastic body.
 
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