3D printed 18650 light, playing with the idea.

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PeterF
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3D printed 18650 light, playing with the idea.

Hello!
Quite some time ago i sparked the idea to build a flashlight, it is a few months later now and i have a rough idea on how to do it.
In my parts bin are about ten 18650 cells, 20 LED drivers, a few Nichia LEDs and a 3D printer, all that needs to be put to good use.
So i am set on these four things, here is what i came up with so far, just made some prints to have something in my hand to play with:

http://imgur.com/qankruB

What i know so far, a 3D printed case seems to be viable (if printed in PETG), heat dissipation of the LED will be a problem, 18650 makes the light a bit too big then i would like to but i do not want to buy new batteries.

LED options:
Nichia NF2L385AR,170 Lumen, 2700K with 83RA
Nichia NF2W385AR,197 Lumen, 5000K with 83RA
Cree MK-R, 350 Lumen, 2700K with 80RA
I am unsure about a lens, either a whide angle or none at all, i want a floodlight.
If possible i want to put a temp sensor in there so the light can regulate the power down if it gets too hot, just a cheap NTC/Resistor solution.

LED Driver with no PWM
Texas Instruments TPS61165,i have 20 of them and they fit the LED nicely.
It has a digital interface and can regulate the current in 31 steps.

With a max LED current of 250mA it gives a resolution of 8mA per step and so the lowest light output is 8mA at roughly 6V.
Since it does not use PWM the main controller can go to sleep once the current is set.

USB rechargable with build in charger
Microchip MCP73833, i still have some of them as well.
It provides a thermal cutoff while charging if the cell gets too hot with a NTC and it has 3 pin status output.
Not too expensive and i really like the 3 pin output.
It indicates “power good”, “charging”, “full” and “fault” with 4 different states instead of just a light that goes on and of.

User interface
Two buttons for power up/down and on/off or whatever idea i got, i do not want a single button.
One RGB charge indicator LED.
One dual color battery level indicator with rough battery level aproximation through cell voltage.
I never tried that and guesstimating the charge of a Li* cell by the voltage alone is not a good idea but it is all i can do with the selected components.
As a controller i have chosen the ATTiny85 because they are cheap, i want a bit more flash then a ATTiny13A and everything else is too expensive and big.

Other things
The cell needs to have a second protection circuit, i am toying with the idea of a Texas Instruments BQ29700 cell protection IC, it is fairly cheap but i hate soldering compoents without legs and this thing is tiny.

The whole, how will i mount and cool the LED is still a bit problematic but solveable.
The electronics should be fairly cheap, all on one PCB with all components on one side except the switches, if possible.
I may have to mount the switches and LEDs on the backside, i only work with 0805 SMD parts and hate leg-less packages, so i am stuck with bigger components.
With 0603 and QFN packages everything would fit on one side.

That is about it, what to you guys think?

Edited by: PeterF on 12/27/2016 - 18:08
Rufusbduck
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Imgur link is bad.
At 250mA max don’t need a temp sensor
The attiny can easily handle voltage sensing and cell protection, protection circuits have parasitic drain.
0805 smd parts will fit on 0603 pads
Is one switch a clicky and the other momentary or is power also an e-switch.
With no parasitic drain a cell will last years just sitting there at nominal voltage.
Don’t gift it or sell it to someone who doesn’t get it. Liion cells can be dangerous with or without protection circuits and ignorance = genius when coming up with unforeseen ways of sidestepping design parameters. no such thing as idiot proof.

Three Tanna leaves to give him life, nine to give him movement. But what if he eats the whole bag?

Scott

PeterF
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Thanks for your reply!

Rufusbduck wrote:
Imgur link is bad.

Sorry, the forum software really does not like the link it seems.!
I can not get the link to work… i re-uploaded it:
http://imgur.com/qankruB

Quote:
At 250mA max don’t need a temp sensor

The test i ran says otherwise, the LED gets too hot with just a bit of aluminium sheet.
That is about 1.5W of heat produced by the LED.

Quote:
The attiny can easily handle voltage sensing and cell protection, protection circuits have parasitic drain.

The drain of the TI part is way lower then the ATTiny in sleep mode, 25µA in operation and around 100nA in shut down, once the UVLO is triggered.

Quote:
0805 smd parts will fit on 0603 pads

My pads are a bit bigger, i hand solder the stuff.
I just do not do this stuff often enough to be able to rationalise reflow soldering from a budget perspective Smile

Quote:
Is one switch a clicky and the other momentary or is power also an e-switch.

Both are soft switches, controlled by the ATTiny.
I expect the circuit to be drawing about 100µA in “standby mode”,
with a battery capacity of around 3Ah i am comfortable with that.

Quote:
Don’t gift it or sell it to someone who doesn’t get it. Liion cells can be dangerous with or without protection circuits and ignorance = genius when coming up with unforeseen ways of sidestepping design parameters. no such thing as idiot proof.

The cell will be build in/non removeable and the charging port is just a micro USB connector, not that much can go wrong with that.
Leaving out proper cell protection, even if the only user is me, is a bad idea.

Rufusbduck
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If it overheats with only 1.5W then you probably need to figure out how to get more than a bit of aluminum sheet in there. I made this one that does just fine at 13.7W(4.5A/3/4V) for short periods and 4.7W(1.5A/3.2V)continuous. In any case I would think it preferable to have stable operation at 250mA max rather than a step down from there. 31 steps from there to 8mA is maybe 28-29 in excess. Not trying to be mean here just my opinion based on experience with 350m lights and at 250mA/6V it’s comparable to .5A/3V which is on par with many single AA lights that don’t get too hot or need very many lower modes.
I think “protection circuit” is a misnomer possibly leading to a false sense of security but if the concern is of a short circuit then not misplaced and I won’t tell you it’s a bad idea. Just don’t forget that you are your best protection. If the cells are to be built in permanently and charged in place then instead of individual cell protection you might consider BMS (battery management system)which monitors each cell individually as well as the battery as a whole both in charge and discharge conditions. You asked for input, that’s my .02.

Three Tanna leaves to give him life, nine to give him movement. But what if he eats the whole bag?

Scott

PeterF
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Hello and thanks again for your reply!

In case i came over a bit grumpy, im sorry, your feedback is apreciated! Smile

 

Rufusbduck wrote:
If it overheats with only 1.5W then you probably need to figure out how to get more than a bit of aluminum sheet in there.

 

Yes, i have been thinking about that, i have come up with another way but i am not too happy about it.

I can do a aluminium body, no problem, but... the whole idea is to make this thing only with a 3D printer, it is kind of a design challenge, just two PCBs and the 3D printed parts with a few screws. Nothing else.

 

A custom aluminium PCB cost about 4 bucks with shipping when i order 10 pieces and i want to use that as integral part of the body, sandwiched between the head and the body of the housing.

So... as a design challenge that is my only "heatsink". At around 100mA that works just fine, at 250mA it gets too warm.

 

Another way would be to just stack two of the aluminium PCBs back to back, that only incrases the mass by double but not the surface area.

 

Quote:

Not trying to be mean here just my opinion based on experience with 350m lights

 

No worries, i never build a flashlight, every feedback is appreciated!

 

Quote:

If the cells are to be built in permanently and charged in place then instead of individual cell protection you might consider BMS (battery management system)which monitors each cell individually as well as the battery as a whole both in charge and discharge conditions. You asked for input, that's my .02.

 

Yes, the protection IC along with the charger form a complete BMS, they monitor the voltage and current during chargeing and discharging including the temperature of the battery itself.

Over voltage, temperature and current protection during charging.

Under voltage and over current during discharge.

 

And the ATTiny with the TI part forms a 2 level discharge protection, the ATTiny shuts the light down below 3.3V and then if it gets further discharged the TI part cuts it completely of at 2.8V before the cell gets damaged.

 

As far as i can make it out that is the "industry standard" for every build in Li* battery in handheld devices like your phone.

You could use a protected 18650 but they cost double what a unprotected cell costs and, this is the important bit, i only have unprotected cells and do not want to buy new ones.

 

Since i use only a single cell i do not have worry about balancing and i get the 6V for the LEDs from the boost driver, i mainly choose this path because the Nichia LEDs are very cheap at just 1,50 Euros and are authentic and i got the LED driver ICs at very low cost.

cia212
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Instead of an aluminum sheet, can you print the top/heatsink with a metallic filament? Filament Innovations has a good aluminum (40%) version that prints pretty well.

PeterF
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Interesting idea, thanks!

I made a very rough mockup on how the thing is supposed to go in 3D printed body:
http://imgur.com/eOZ0YV5

Not the real shape and form but so not too much has to be imagined.

Rufusbduck
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Maybe even print metallic filament fins?

Three Tanna leaves to give him life, nine to give him movement. But what if he eats the whole bag?

Scott

wle
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a 1xAAA would be super light, as well as having less heat issues…

heat is only an issue with high output – 18650 can have low output too Smile

wle

Rufusbduck
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The wattage he’s considering is already comparable to a single AA light. It’s not the cell he’s using but the lack of enough metal to disperse the heat. At the moment the design is of a point source for heat surrounded by insulation. I’m intrigued by the possibilities and the metallic filament might be enough to solve the issue.

Three Tanna leaves to give him life, nine to give him movement. But what if he eats the whole bag?

Scott

PeterF
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I think i came up with a semi-decent solution that should work:

http://i.imgur.com/OFcwDGC.jpg

Since the PCBs are damn cheap i can just use two and put two spacers between them and screw the whole sandwich together.
The spacers are easily made since they are just two aluminium tubes, maybe i can even glue them together with thermal adhesive.

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A few months back I made a 3D-printed 18650 light. It’s a wide-area camping light, running 8 XP-Ls in series on a boost converter from 2 series 18650 cells. It was primarily made as a test of hacking the MT3608 boost converter modules to turn them into constant-current LED drivers. It actually works pretty well – you can dim by PWMing the enable pin, as long as the frequency is pretty low. This one is boosting from 8V to 24V at 500mA (output). The firmware is my basic single-channel momentary switch UI, which is essentially a stripped down version of MELD. I mentioned in the video below that I made it open source, which I thought I had, but now can’t seem to find where it’s stored! If anyone is interested I will be happy to share the source code.



A quick demo video:

PeterF
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Thanks for the reply!

You have no problems with the heat in that setup?
It looks like you mounted all the emitters on one sheet of aluminium and sandwiched that between the case halfs?

tterev3
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PeterF wrote:
You have no problems with the heat in that setup? It looks like you mounted all the emitters on one sheet of aluminium and sandwiched that between the case halfs?

Yep it’s just a 1/8” sheet of aluminum that comes all the way out to the outside edges. I ran it for about an hour while camping at probably ~50% power and it had no issues with temperature. I haven’t run it at maximum (12 Watts) for any significant time though, it would probably get pretty hot if I did.

PeterF
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I think i finally got a decent way to get the thing cooled, ill try to get something drawn tomorrw and post it.

Maybe someone is still interested Smile

cia212
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Forgot to ask what kind of 3D printer you have.

PeterF
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cia212 wrote:
Forgot to ask what kind of 3D printer you have.

It is a “Duplicator I3 V2.1” that is often re-branded as a “Monoprice Duplicator I3 V2.1”, it is a damn nice printer for the price i think.
The prints look way better then i thought they would be, very happy with it so far:

http://imgur.com/a/aBbus

PeterF
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This seems to be a viable solution, it is not pretty but gets the idea across.
I upgraded to two Nichia LEDs, they get to around 394 Lumen for cold white and 338 Lumen for warm white at max current.
This perticular type is used because i can get them for only 79 cents a piece and they run at 129 and 159 lumen per watt efficiency at 100mA.
Those are pretty good numbers for the price it think.

This still is a very odd combination of parts and LEDs used but the idea is odd in general.
Since the metal core PCBs are rather cheap i can just use 3 of them, one has the LEDs on it, the others just serve as a heatsink, if that is not enough i can just stack more PCBs for more surface area.
Everything sandwiched together with spacers and M3 screws, M3 since i use them everywere in my projects allready.

The cables for the LEDs go through two small aluminium tubes that to through the stack, they serve as alignment pins as well.

There is no optic, this is very intenionally a flood light, the “lens” i plan to use is from a LED strip cover.
A mock up with some duct tape and my bench supply and the two LEDs that i have showed that the beam looks nice that way, it looses a bit of brightnes but finding a proper optic for this was not easy.

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Ledil makes some interesting shapes for optics. It’s looking more reasonable now.

Three Tanna leaves to give him life, nine to give him movement. But what if he eats the whole bag?

Scott

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I hope you put those Ultrafire cells to recycling soon
Such nice emitters and then those 600mAh fire ells

tterev3 wrote:
A few months back I made a 3D-printed 18650 light. It’s a wide-area camping light, running 8 XP-Ls in series on a boost converter from 2 series 18650 cells. It was primarily made as a test of hacking the MT3608 boost converter modules to turn them into constant-current LED drivers. It actually works pretty well – you can dim by PWMing the enable pin, as long as the frequency is pretty low. This one is boosting from 8V to 24V at 500mA (output). The firmware is my basic single-channel momentary switch UI, which is essentially a stripped down version of MELD. I mentioned in the video below that I made it open source, which I thought I had, but now can’t seem to find where it’s stored! If anyone is interested I will be happy to share the source code.



A quick demo video:

PeterF
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Thanks for the reply!

Rufusbduck wrote:
Ledil makes some interesting shapes for optics. It’s looking more reasonable now.

My main problem is, that i went from a single LED to two and want as close to a 90° beam angle as i can get.

That makes the choice of lens… difficult, for a single LED there as plenty of lenses available, not so much for two.
But i think i am fairly happy with the thing i found, 50cm cost <5 bucks and i can saw at least 40 out of them, pretty good bang per buck.

PeterF
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The head is mostly sorted out, the next step is trying to fit everything else together.
This is a very rough sketch on how the internals are held together, i just wanted to shove everything into a tube and slather it in hot glue but i want it to be pretty on the inside as well.
There is not a big chance that i will be able to get away with those buttons, most likely i will have to use low profile ones.
That means i got to figure out how to mount buttons caps on the thing.

I mainly have to figure out the rough size of the PCB and how to mount it.
Then route the whole thing so i can model the body and button caps for the PCB.
The main issue is, how i get the USB plug poking out somewere at the bottom.

Since i want to use screws in the base it will be a bit thick…

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Slow and steady progress, before i can finalise all the dimensions i got to figure out how to do the switches and cover for the micro usb connector.

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i build many lights that are sealed, up to 700-800ma on a chink of aluminum, or copper under the star is enough, it does get hot, but it never went over 70c, measured at the star, none of the leds visibly degraded, my plastic surefire g2 with 700ma drop in, has no issues either, no visible degradation, it is still as bright, to the eye, as it was the first day i turned it on, even thou the pill is brass.

PeterF
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alpg88 wrote:
i build many lights that are sealed, up to 700-800ma on a chink of aluminum, or copper under the star is enough, it does get hot, but it never went over 70c

Thanks for the reply!
I want to stay below 60°C on the heatsink, in case i want to print it in PLA.
It should be no problem i think with 3 PCBs as a heatsink.

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at 250ma max you shoudl be fine, how thick is your mcpcb? is it direct path, or insulated one?

the gap between mcpcb looks too small to be effective for passive cooling, but with your low current, it shoudl not be an issue, i’d use 1pcb but thicker. or have a pcb with a skirt.

PeterF
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Hello and thanks for your reply!

alpg88 wrote:
at 250ma max you shoudl be fine,

Thanks! It is 250mA at 12V though, both leds have two dies, four in total.
Bit strange but a product of a few design variables, most likely i will run them at just 200mA.

Quote:
how thick is your mcpcb? is it direct path, or insulated one?

The quote i got is for a regular 1,6mm board, everything else is too expensive, that includes insulation on all pads.
One of the reasons i wanted to use two LEDs is that the heat is not all produces just in one spot/LED.

Quote:
the gap between mcpcb looks too small to be effective for passive cooling, (…) i’d use 1pcb but thicker.

Since the whole thing is just stacked together, the gap can easily be expanded or a few PCBs can be stacked together without a gap.
I got a lot of room for experimentation there.

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that chages things, 1,6mm is too thin, imo, 250ma at 12v is about 3W, you are basically running 3w on pcb alone. that is too much. in my experience anything higher than 50-70ma (at 3v) is too much for star alone. puting stack of pcd’s on studs isn’t gonna help much, i’d use an aluminum “puck” that is shaped like pcb and put pcb with led on it firmly.

PeterF
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Now that i got a rough idea how much space i got for the PCB i want to make sure the electronics even work properly before i print parts.
A bit of late night tinkering, most likely with a bunch of mistakes…

Here is a first draft of the schematic:
http://i.imgur.com/dZj5LCs.jpg

Charger, LED driver and Battery protection, it looks like i might have to use a ATTiny84 instead of a ATTiny85.
The lack of pins that leads to compromises does not sit too well with me.
The 6 more pins i can put to good use.

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alpg88 wrote:
that chages things, 1,6mm is too thin, imo, 250ma at 12v is about 3W, you are basically running 3w on pcb alone. that is too much. in my experience anything higher than 50-70ma (at 3v) is too much for star alone. puting stack of pcd’s on studs isn’t gonna help much, i’d use an aluminum “puck” that is shaped like pcb and put pcb with led on it firmly.

Hmm? 50ma? A star alone should be able to handle 3w and keep the light below 60. I put a star in a plastic headlamp at 1amp and it does fine. That is with less effitient emitter as well. But maybe someone who has done some tests with data logging could chime in?

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