Choosing components: DIY surgical headlamp

RadioCured · 2018-08-12T15:39:05.000Z

Hello everyone, this is my first post on BLF!

I'm a casual flashlight enthusiast and surgical resident. Being familiar with flashlights and LEDS with advancements in tint and CRI, I've been disappointed to see the offerings for surgical loupe mounted headlights - invariably these are marginally bright enough, cool-tinted, and ridiculously expensive for what is being offered.

I followed the BLF Q8 development and dipped my toes into modding with a spring bypass on my own Q8. Obviously I have a lot to learn and take in, but I'm certain I can build something much better for far less money. I'm also getting into 3D printing and modeling in Fusion 360, so I'd like to build something from the ground up. I need some help with the basics of choosing proper components as a first step to seeing if this is feasible.

This is the sort of product I'm hoping to emulate and improve upon:

https://www.orascoptic.com/products/headlights/endeavour-xl

These retail for more than $600!

Characteristics I'm aiming for:

- Battery (3-4x 18650) and driver housed in a hip mounted pack, leaving only the light weight LED/PCB, small heat sink, and lens mounted on my loupes

- At least 100 OTF lumens. I'm not sure how these companies are measuring light output, but Orascoptic claims 85 lumens on their more powerful light.

- Even beam filling the field of view through the magnified loupes. The example I linked claims 2.5" beam at 12" working distance, which should be about right. I'll likely need a convex/aspheric lens like in a cheap zoomie light to achieve even brightness across the beam. I know I'll lose a lot of output this way, but I think the even light will prevent distracting changes with small head movements

- Neutral white tint with high CRI to match overhead operating room lights

- Continuously adjustable brightness would be nice, either with a potentiometer or through firmware like Narsil

Here is what I have come up with so far:

LED:

CREE XP-E: small size should result in more efficient light output for an aspheric lens in fixed "zoom" configuration. I can adjust the lens distance as needed to create the perfect final spot size at my working distance. I found these on some fairly small PCBs:

https://www.aliexpress.com/item/Hot-Sale-5PCS-Cree-XLamp-XP-E-Blue-470-475NM-1W-3W-LED-Light-Emitter-w/1393000761.html

The PCB size and whatever heat sink I devise will likely be the limiting factor in how much light output I can get from this device since there isn’t a whole lot of mass to pull heat away

Lens: I think around 20mm will provide a good balance of capturing enough light and not being too obstructive or heavy. Any input on selecting a size?

https://www.aliexpress.com/item/2pcs-20mm-23mm-25mm-28mm-36mm-42mm-45mm-50mm-PMMA-Lens-for-CREE-Q5-R2-R5/32809626913.html?spm=2114.search0302.3.17.556156af39hsUE&ws_ab_test=searchweb0_0,searchweb201602_0_10130_10152_10151_531_315_10618_10059_10696_10084_100031_10083_10547_10624_10546_10623_10307_10548_10341_10065_10340_10068_10343_10342_10103_10620_10344_10325_10545_10622_10324_10621,searchweb201603_0,ppcSwitch_0&algo_pvid=1daaae56-9b7f-4647-b648-86df0777b625&algo_expid=1daaae56-9b7f-4647-b648-86df0777b625-2

Driver:

This is where I need the most help.

To figure out the output current I’ll eventually need I’d like to estimate OTF lumens based on the efficiency of the aspheric lens. CREE publishes luminous flux for all their LEDs which I assume is the total lumens out. Does anyone have a formula or resource for finding out how much will make it out the front?

I’m fine with using either a driver designed for a flashlight or a larger one since either way it will be hidden in the battery pack.

Some firmware with continuously adjustable brightness or ability to use a potentiometer would be ideal. Are there drivers from BLF lights available?

A few possibilities that I’ve found so far:

https://www.ledsupply.com/led-drivers/buckpuck-dc-led-drivers

https://www.ledsupply.com/led-drivers/flexblock-buck-boost-dc-led-driver

http://www.dx.com/p/wy6890-drive-board-switch-board-for-head-lamp-car-light-green-162781#.W3BOJi2ZMlJ

Let me know what you think and if you have any suggestions!

Lightbringer · 2018-08-12T16:07:13.000Z

“Cree” and “high-cri” generally aren’t used in the same sentence. Nichia 9080s would be better.

Better would be interchangeable 20mm TIR lenses, variable angles (spot to flood), pebbled. They mix LED light nicely and minimise tint-shift.

Look into bike-light styles, small head and remote battery-pack.

zak.wilson · 2018-08-12T16:36:37.000Z

The XP-E doesn’t seem like a particularly appropriate LED for this. The Nichia E21A in your choice of color temperature would be ideal. If color matters, these are some of the best. They’re available here along with appropriate MCPCBs.

A driver with a single 7135 would be sufficient for over 100 OTF lumens with a decent honeycomb TIR. You could run two of them for 200+ lumens without it running terribly hot. A buck driver would be more efficient, but at 350mA, you’ll be getting nearly 10 hours per 18650 in your battery pack, so that’s probably not a huge concern.

gravelmonkey · 2018-08-12T16:36:54.000Z

Lightbringer:

“Cree” and “high-cri” generally aren’t used in the same sentence. Nichia 9080s would be better.

Better would be interchangeable 20mm TIR lenses, variable angles (spot to flood), pebbled. They mix LED light nicely and minimise tint-shift.

Look into bike-light styles, small head and remote battery-pack.

This is good advice.

I’ve seen a DIY surgical lamp used in a vet practice using a cheap Chinese headlamp mount and a modified 18350 convoy S2. Dummy cell used with contacts wired through the tail clicky to an external battery pack. I don’t have any further details but it looked like a tidy build.

Bob_McBob · 2018-08-12T18:46:47.000Z

How about Optisolis for this?

Lexel · 2018-08-12T19:00:34.000Z

100 lumens would run from a single 3500mAh battery about 10 hours straight at full brightness, 4x is overkill

if you look in my signature or topics you see I am building and selling drivers of all kinds and sizes

a Driver based on NarsilM Ramping would my be favorite, utilizing a simple button,
which could be even placed on the lights body

2 channel each one AMC with 350mA
double click for turbo any current up to 700mA (190 OTF Lumens)
ramping from 0.01 Lumens to any value you want like 85 Lumens

Nichia 9080 takes only about 300mA for 100 OTF Lumens

here the output from a 9080 Nichia

Nichia 219B 4500k D220 9080 CRI Emitter output test by Texas_Ace; Amazing tint and CRI! Output is what you would expect. Flashlight Modding and DIY Parts

Ok, like normal, tests done the same as all my others. These are the 219B 9080 CRI (basically the highest CRI you can get in a high powered LED). These are not meant as output monsters but as tint beauty queens. I tossed one on the bench just for giggles. The tint is really great, on the rosy side for sure but the CRI really makes colors pop. I have not put one in a flashlight yet so can’t comment too much on it. Output is pretty run of the mill for a 219B, pretty good for such a high CRI LED…

Lightbringer · 2018-08-12T21:26:10.000Z

If you’re feeling adventurous, you can even swap an S2+ with shorty tube, simple 1×– or 2×–7135 driver, and remove the switch (“rubber-boot” type, not the metal switch) and pack the boot with silicone to make it watertight, then run the wire directly to the driver, and out back to whatever battery pack you want with reverse-clicky switch.

Bap the switch to change modes. You can probably flash the driver (nanjg) with whatever firmware you want. Make it 20 brightness levels if you want.

There are a few headbands made for tubelights like the S2+. Go crazy…

manithree · 2018-08-12T22:02:23.000Z

This is probably overkill (higher current, more lumens, more batteries) than you need, but I saw this the other day and wanted the battery pack and driver:
Brett Headlamp

Since it’s set up for an XHP70, I think that means it should work with a high CRI Nichia E21 since, IIRC, they’re both 6V emitters.

Maybe mod one of these with a virence board and emitter. I have no idea how feasible any of my harebrained suggestions are, since both items are on my want list but I haven’t purchased either of them yet.

Phlogiston · 2018-08-12T22:09:58.000Z

I’ve heard of operations taking 8 hours (perhaps longer still?).

As others have said, a single 18650 would do 100lm for about 10 hours, but I can understand why a surgeon might want more than that to make absolutely certain he doesn’t get caught short. The last thing you want is a cell change at a bad moment.

Two 18650s wouldn’t be drastically bigger, but double the runtime, so you’d have time for unexpected overruns and also extra capacity for unnoticed aging of the cells reducing their capacity.

3 or 4 18650s would run for a lot longer than I’d want my surgeon to be awake but there could still be a use for that if the unit needed to be reused in an emergency without having had time for a full recharge.

Having the extra 18650s also helps avoid running them down to lower voltages that might cause the driver circuit to drop out of regulation.

Many people consider Nichia’s high CRI LEDs to have a more natural tint than Cree’s high CRI offerings. I’d strongly recommend trying LEDs from both manufacturers as you refine your prototype.

Some people react poorly to PWM, either because they can see the flicker and it distracts them, or because they get headaches even without consciously seeing the flicker.

I would lean towards constant current for this project. Rather than use a flashlight driver, I’d consider an adjustable constant current regulator, which would allow you the potentiometer control you want. At the likely 350mA range - or even 500mA to give a bit of leeway - even a relatively simple, linearly regulated circuit would be dissipating well under than a watt, which isn’t too bad for heatsinking, given the likely space available within a belt-mounted powerpack.

I presume this device needs to be sterilised; sealing your enclosure well enough to withstand that will take significant work. Alcohol is really good a getting round seals, for example, and will perish some rubbers and plastics. You can’t autoclave something with a Li-Ion cell in it; the 100+ °C of an autoclave drastically exceeds the 50 - 60°C maximum for a Li-Ion cell.

You might consider swappable battery packs, so that they can be permanently glued shut - no alcohol leaks - and swapped out for recharging, as long as you use a locking connector to avoid it being pulled apart by accident in use. Obviously, your connectors will have to be a type that won’t allow liquid ingress. I don’t know if it’s practical to have a battery box with a wire to a control box with another wire to the loupe-mounted light emitter?

Finally, beam profile: a beam that’s 2.5 inches diameter at 12 inches is about 12° in diameter. As Lightbringer says, you can get TIR optics going from 5° to over 60°, in clear, pebbled or frosted types to achieve all manner of beam profiles. They’re cheap enough for you to buy several types and experiment to your heart’s content.

The beam is affected by both the TIR and the LED you use, so you’d definitely need to try different combinations to make sure you got the best result. That’s no loss, though, because similar issues apply to reflectors and aspheric lenses.

Is it a problem if the beam spills some light beyond the 12° you’re looking for? You might have to set the LED / optical assembly quite deeply into a black tube if you need a sharp cutoff at the edge of the beam. A 20mm optic would need to be set inside a 90 - 100mm tube for that. It is possible to get smaller optics, though; a 10mm optic would get that down to 45 - 50mm, for example.

All in all, an interesting project!

RadioCured · 2018-08-26T22:56:15.000Z

Thank you everyone for the responses so far! Sorry for the delay in getting back to you. I've taken your advice into account and have put together the following parts. Let me know what you think!

LED and PCB:

- Nichia E21A 5000k mounted on a 16mm PCB from Virence

https://www.virence.com/product-page/vr16s1

- I also ordered a few other cheaper Nichia 219C mounted to a 16mm PCB to play around with while I'm experimenting

Driver:

https://www.ledsupply.com/led-drivers/buckpuck-dc-led-drivers

I'm thinking of going with this 500mA constant-current driver with built in potentiometer. The voltage range required (7-32v) should work well with 3x 18650 in series. Advantages I see here:

Simple UI, just on/off and brightness control
Ability to trim the output with the build in trim control if a full 500mA creates too much heat at the PCB
Easy to place inside housing
Easy to wire to other components with less critical soldering operations

Most people thought 3 batteries was overkill, but sometimes we have 12+ hour days, and I would like the light to be able to last for several days between charges. Also, the extra size and weight is less of a problem in a waist mounted battery pack.

Lens:

I ordered a variety of different 20mm Carclo TIR optics as well as a few 20mm convex lenses so I can try different configurations

Charger:

Here I need some help again. I would really like to include the ability to charge the batteries via micro USB instead of having to remove them every time. This way I could charge on any cell phone charger or from a computer USB if necessary. It would also make my enclosure design less critical - I can use screws instead of having to design a battery door or something for easy access.
I found this really nice little charger circuit, but it's obviously built to charge to 4.2v. Since I'm planning 3 batteries in series to run my driver, is there any way to include this or something like it? http://www.mtnelectronics.com/index.php?route=product/product&product_id=135
Here's another charger which seems to have flexible input and output. Would this be safe to use to charge 3 18650s in series using an old laptop charger? http://www.mtnelectronics.com/index.php?route=product/product&path=79&product_id=136

Other:

1/8" aluminum stock to cut some heat sink for the PCB to mount to - is this necessary for my intended output or will the PCB alone be sufficient?
3x 18650 battery pack https://www.banggood.com/New-Version-DC-11_1V-3-Slot-3-Series-18650-Battery-Holder-Box-Case-With-2-Leads-And-Spring-p-1269512.html?rmmds=buy
Will need some thermal epoxy at some point

Phlogiston mentioned sterilization - this will not be a concern as the light does not have to be sterilized in any way. During surgery the only the region from the hips to the chest are considered sterile. We wear clean caps to keep hair out of the operating field and masks to prevent spreading bacteria from nose/mouth, but glasses, loupes, head lights, shoes, etc are not actually sterile. For this reason any buttons or control mounted to the light would not be helpful, so controls at the battery pack that can be adjusted through the sterile surgical gown are necessary.

Let me know if you have any more suggestions!

skinny_tie · 2018-08-26T23:36:39.000Z

I can’t find the thread right now, but I think BLF user Clemence (owner of virence.com) designing a headlamp for a surgeon so it might be worth discussing the project with him.

Barkuti · 2018-08-27T01:40:38.000Z

If this serves anything, about a couple months ago I modified a reflector based headlamp with this marble grain TIR lens from Yajiamei Optics: https://www.aliexpress.com/item/led-lens-35-8mm-Marble-grain-Led-reflector-lens-power-1W-3W-lenses-LED-Optical-lens/1320075802.html

Very nice, uniform wide beam.

Cheers ^:)

Barkuti · 2018-08-27T02:00:23.000Z

By the way, in the opening post there's a link which seriously messes up with the page format, the one to the AliExpress' aspheric lenses sale in Professional Outdoor Lightings: https://www.aliexpress.com/item/2pcs-20mm-23mm-25mm-28mm-36mm-42mm-45mm-50mm-PMMA-Lens-for-CREE-Q5-R2-R5/32809626913.html

If you don't mind, RadioCured, you could edit it and replace that page format messing link with the tidied up above one. Damned links full of bullsheesh…

Cheers ^:)

Yokiamy · 2018-08-27T05:27:46.000Z

You need the cells in parallel, in series won’t give the required runtime.
What about the amutorch SS (AA/14500) modified to a surgical light?

Phlogiston · 2018-08-27T14:48:54.000Z

RadioCured:

Charger:

Here I need some help again. I would really like to include the ability to charge the batteries via micro USB instead of having to remove them every time. This way I could charge on any cell phone charger or from a computer USB if necessary. It would also make my enclosure design less critical - I can use screws instead of having to design a battery door or something for easy access.

I found this really nice little charger circuit, but it’s obviously built to charge to 4.2v. Since I’m planning 3 batteries in series to run my driver, is there any way to include this or something like it?

As you know, you won’t be able to use that to charge 3 cells. Don’t be tempted to try and wire 3 of them with one per cell - even if you use 3 separate USB cables, many USB power supplies are wired in a way which will create a short circuit in that configuration.

For 3 cells in series, you’ll need a BMS (“battery management system”) module (a.k.a. “balancing charger”) with balancing connections to each cell. As you already know, you’ll need a higher voltage power supply for that.

RadioCured:

Phlogiston mentioned sterilization - this will not be a concern as the light does not have to be sterilized in any way. During surgery the only the region from the hips to the chest are considered sterile. We wear clean caps to keep hair out of the operating field and masks to prevent spreading bacteria from nose/mouth, but glasses, loupes, head lights, shoes, etc are not actually sterile. For this reason any buttons or control mounted to the light would not be helpful, so controls at the battery pack that can be adjusted through the sterile surgical gown are necessary.

That’s interesting, I didn’t know that. Learned something new today

Yokiamy:

You need the cells in parallel, in series won’t give the required runtime.

If the driver is a switch-mode buck driver with reasonable efficiency, then the runtime will be unaffected by whether the cells are in series or in parallel. Part of the prototyping process would obviously include runtime tests to make certain of that.

RadioCured · 2018-09-04T13:35:01.000Z

Phlogiston:

As you know, you won’t be able to use that to charge 3 cells. Don’t be tempted to try and wire 3 of them with one per cell - even if you use 3 separate USB cables, many USB power supplies are wired in a way which will create a short circuit in that configuration.

For 3 cells in series, you’ll need a BMS (“battery management system”) module (a.k.a. “balancing charger”) with balancing connections to each cell. As you already know, you’ll need a higher voltage power supply for that.

I’ve been looking at these series charger modules which would allow me to charge up to 3 cells in series using an external power adapter. Pairing this with a BMS module to ensure the cells are charged equally without over or under charging any I think may be a good solution. Any thoughts on these components?

https://www.ebay.com/itm/MAX745-Step-Down-Charging-Board-for-1-4-Packs-4-2V-4-35V-Lithium-Battery-adjust-/201426143584

banggood.com

Banggood Sitemap - Wholesale Sitemap - China wholesale

China wholesale Sitemap, dropshIP wholesale from China, Professional Chinese wholesaler for general merchandise on wholesale price.

https://www.amazon.com/TAIFU-Switching-Converter-Adapter-Interface/dp/B071RKBW51/ref=sr_1_4?s=electronics&ie=UTF8&qid=1535583879&sr=1-4&keywords=15v+2.5A+power+supply

In general how reliable are these cheap electronics components? Would you still recommend using protected cells for a setup like this for extra reassurance, or do you think these BMS modules are more reliable than the small protection circuits on 18650s anyway?

This video is close to what I’m aiming to assemble, minus the voltage step up because I plan to use a 15v charger: https://www.youtube.com/watch?v=SyiUzZJHVx8

It would probably save a lot of headache to find a lower voltage driver that can run on 2-3 cells in parallel so I can use the micro USB chargers, but I haven’t been able to find one that can be controlled using a simple potentiometer. I would at least like one that allows for very simple high-medium-low selection separate from the power switch.

Barkuti · 2018-09-04T17:10:35.000Z

RadioCured:

… Any thoughts on these components?

https://www.ebay.com/itm/MAX745-Step-Down-Charging-Board-for-1-4-Packs-4-2V-4-35V-Lithium-Battery-adjust-/201426143584

https://www.banggood.com/3S-20A-Li-ion-Lithium-Battery-18650-Charger-PCB-BMS-Protection-Board-12_6V-Cell-p-1118043.html

https://www.amazon.com/TAIFU-Switching-Converter-Adapter-Interface/dp/B071RKBW51/ref=sr_1_4

In general how reliable are these cheap electronics components? Would you still recommend using protected cells for a setup like this for extra reassurance, or do you think these BMS modules are more reliable than the small protection circuits on 18650s anyway?
…

These electronics aren't exactly the cheapest options. First of all, your MAX745 charging module, but cheaper:

https://www.ebay.com/itm/Switch-Types-1-4-Series-Li-ion-Lithium-Battery-Charge-Board-Regulator-Buck-Modle/183358555853
https://www.ebay.com/itm/Step-Down-Charging-Boards-Current-Voltage-for-1-4-Series-Li-ion-Lithium-Battery/202388385772

For even cheaper:

https://www.aliexpress.com/item/5A-DC-to-DC-CC-CV-Lithium-Battery-Step-down-Charging-Board-Led-Power-Converter-Lithium/32864870509.html Proven good XL4015 buck modules, fully voltage and current adjustable.
https://www.aliexpress.com/item/-/32855809021.html Same as above, but different seller, price and shipping options.
https://www.aliexpress.com/item/5A-DC-To-DC-CC-CV-Lithium-Battery-Step-Down-Module-Charging-Board-LED-Power-Converter/32799532951.html Same stuff again, I usually wishlist two or three sales of the same item if I buy it often.
https://www.aliexpress.com/item/New-Upgrade-3S-40A-BMS-11-1V-12-6V-18650-lithium-battery-protection-Board-with-balanced/32838253888.html Beefy 3S BMS with balance, I have one running inside a battery overhauled Bosch PSR 1200 drill.

With regards to the power supply there are plenty of inexpensive 15V power adapter offers out there, for example:

https://www.aliexpress.com/item/High-Quality-AC-DC-15V-2A-Power-Adapter-Supply-Charger-15V-1-2A-adaptor-UK-UE/32767135327.html

Or brand name 19V laptop power supplies for cheaper than $17.59.

Reliability speaking, these electronic devices usually are very reliable. And do not mess with protected cells if using a BMS, that won't end up well. A BMS is a battery management system, this includes protection circuitry.

Cheers ^:)

johnhunt · 2019-01-18T18:39:33.000Z

Can anyone help me with this question? I’ve got a very expensive LED light on my loupes-connected by a cable to a two pin co-axial plug and into a rechargeable battery pack. After a few years use, the black plastic cable cracks, and a green fluid seeps out. What is this??
I just contacted Orascoptic to buy a new lead with new lamp ( it’s a sealed unit, of course…the last thing they want is people repairing things)…guess what…no longer manufactured, but will happily sell me a new light and battery for £1000+

The cable is in good order where it comes out of the lamp, and at the co-axial plug end. Could I splice/ join some new cable somehow? …and what sort of cable.

Any help/ advice appreciated.

Yokiamy · 2019-01-18T19:05:44.000Z

johnhunt:

Can anyone help me with this question? I’ve got a very expensive LED light on my loupes-connected by a cable to a two pin co-axial plug and into a rechargeable battery pack. After a few years use, the black plastic cable cracks, and a green fluid seeps out. What is this??
I just contacted Orascoptic to buy a new lead with new lamp ( it’s a sealed unit, of course…the last thing they want is people repairing things)…guess what…no longer manufactured, but will happily sell me a new light and battery for £1000+

The cable is in good order where it comes out of the lamp, and at the co-axial plug end. Could I splice/ join some new cable somehow? …and what sort of cable.

Any help/ advice appreciated.

If you could upload some pictures (on a 3rd party hoster) and link to them, that would give us more information, and we’ll try to help !

hank · 2019-01-18T23:12:42.000Z

I’ve had spring earhooks for eyeglasses split and green gunk seep out — it’s copper corrosion in that case.
Gooey not runny/liquid though.