Building the perfect medical penlight

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atomix's picture
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Joined: 07/20/2019 - 18:16
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Location: Germany
Building the perfect medical penlight

As a med student I now need a penlight to look at patients. What I’ve noticed with most available “medical penlights” is, they either

  • use incandescent bulbs, which have a really inhomogeneous beam and do not portray colours accurately (yeah the CRI is 100, but it is still very warm yellow light)
  • use cool white 5mm LEDs, which is way worse.

So I’ve decided to build my own, using the Lumintop IYP 365 as a host, because it looks very sleek (no giant Nitecore logo on the side) and has a good clicky, which seems pretty hard to activate accidentally. Now, while this is already a better light than what most doctors use, there is still a few things I want to change:

  1. The LED: It comes with a 219C which is already pretty good, but because of the low R9 I want to change it to a E21A
  2. The beam: I would prefer a flat “inspection style” beam instead of a hotspot and spill, so the light intensity is the same everywhere I point it at.
  3. Modes: The lowest mode on the IYP is way too low for my taste and two modes (medium, for checking pupils, and high for general examination) is enough and less confusing. Also: No mode memory! Accidentally roasting someones retinas because you forgot the last setting you used should be avoided.

Now, I still need some help/advice with those three issues:

  1. I’m assuming I can just switch out the LED, because the forward voltages (219C: 3.0V, E21A: 3.0-3.3V according to the data sheet, if I remember correctly) are very similar, right? It’s not a high powered light anyway.
  2. So far I have spraypainted the reflector black, which almost completely erases the hotspot. But this feels very unelegant, because that way I lose a lot of light. Does anybody know where to buy a small TIR, or better an aspheric lens which I can fit in there? The inner tube diameter is 12mm and I think there is about a 7mm distance between the lens and the LED.
  3. How can I reprogram the driver, or where can I find a suitable one which I can program myself? I’ve seen a 10/11mm FET driver on MTN Electronics, but I’m assuming direct driving a 3.0V LED with 3.0V from two AAA batteries won’t work out? I also took out the driver in my Tool AA for inspection, and it has a small 6 pin IC (probably a microcontroller), so I’m thinking the IYP will have something similar, but while I have limited experience with embedded programming, I could need some firmware which I can modify… The markings “LBPJ” on the IC also didn’t tell me what kind of uC it is and how I can reprogram it.

I’m thankful for any helpful pointers Smile

HenrysCat's picture
Last seen: 1 week 15 hours ago
Joined: 02/23/2019 - 12:50
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How about this one? soft/warm light and white light all in one + USB rechargable.

korpzgrinda's picture
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If you can’t find a suitable lens, maybe an application of DC-Fix will help to smooth the beam profile.

Last seen: 1 hour 42 min ago
Joined: 03/10/2019 - 14:28
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Location: USA

You would be surprised at just how little you need your own personal light. If you must build your own light then I recommend a high CRI warm light w/ as little flood as possible. Probably max lumens 50 or less.

Flying Luminosity
Flying Luminosity's picture
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Wuben have just released a High-CRI penlight.

The_Driver's picture
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Location: Germany

The light needs to be waterproof and should have a simple, "flat" body style so that it can easily be desinfected.


It should also have a very robust switch. I modded a Thrunite Ti4 Ti with a Nichia 219B R9080 for a friend of mine who is a doctor. After about 2-3 years the switch became unreliable and Thrunite doesn't keep replacement tailcaps in stock for older lights. After waiting for the replacement switch to arrive I need to put it into the tiny tailcap (quite difficult).

BabyDoc's picture
Last seen: 1 day 6 hours ago
Joined: 05/29/2019 - 09:37
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Location: Beachwood, Ohio

Check out the Nitecore MT06MD.
It is a high Cre medical flashlight, that I personally use and recommend. It doesn’t have a well defined hotspot, which makes medium mode great for looking in the mouth and pharynx. It has low, medium, and high modes in that order, which I like, so that I don’t ever accidentally “blind” a patient, as I begin my exam. However, I do wish, the low mode at 4 lumens was a bit lower.

Lumintop also makes a highly regarded IPY365 hi Cre penlight. There is little need to modify it. It starts in medium mode, then low, and finally high. Its low mode is 1.5 lumens, which is useful when checking extra occular movements. (You will have patients squinting with 4 lumens. You will seldom use high mode with either light.)

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Sorry for my bad English (gogole transtorla)

buck91's picture
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Location: Michigan

Not as nicely finished as the IYP365 but something like the Gerber Foreman with a Yuji swap might be nice. When I was in the field I just used a Solarforce Z1 and put up with the cold white. Had a nice low moonlight at least. Now that I’m inside I just use the wall mounted ottoscope.

If I went back into EMS I’d go with something like the Eagtac D25C with the 219. Or swap an SST-20 into your choice of host originally equipped with the XPG/2.

Last seen: 1 month 5 days ago
Joined: 04/06/2015 - 14:06
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Location: Sweden

Another med student here. Did you consider using Convoy S2 as host? I’m investigating on building the perfect med-light myself.

Last seen: 4 hours 10 min ago
Joined: 05/23/2019 - 21:59
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Location: CA, USA

Wouldn’t an S2 be way thicker than a penlight?

korpzgrinda's picture
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Yeah, I don’t think an S2 is going to fit well in the chest pocket of a lab coat.

Big_Sam's picture
Last seen: 9 hours 19 min ago
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Location: UK

This is a great project! I really like the idea for a good rendering penlight.

Have you though about bringing out a second version with a 485-500Nm Blue LED, this is very useful for using with fluorescing dye for checking eyes ( I had a doctor friend ask me to find a blue pen light for eye exams, ended up with a blue LED Niteore tube which works well).

The ones available on medical supplies websites are usually incandescent with a terrible blue filter.

This is the Nitecore Tube Blue:

Giveaways running until 31st Jan:

Lick's picture
Last seen: 4 weeks 1 day ago
Joined: 10/19/2015 - 14:53
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guardior wrote:
Another med student here. Did you consider using Convoy S2 as host? I'm investigating on building the perfect med-light myself.


This is a brilliant idea, he can use a 18350 tube, and a diffused lens, with maybe 1x or 2x 7135 chips. Wouldn't be too hard, the SST40 sounds like a great led for it as well.


Last seen: 7 hours 56 min ago
Joined: 06/02/2013 - 16:56
Posts: 929
Location: France

Its a shame you destroyed the reflector. The solution was to replace the glass with a frosted glass or sticking a frosted film.

For the LED : SST20 4000k LED This is a good LED with 95 CRI not too warm and the 10mm star will fit the light. Its easy to replace but you will need a little thermal paste for good heat contact.

The no memory driver is positive because you always know what mode the light will turn on. The IYP 365 is an excellent light.

RobertB's picture
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I gave an IYP365 219c to a Physician friend of mine and he loves it.

It looks like Lumintop has discontinued the IYP365, and has the IYP25 now. No idea how the modes work, but medium is now 70lm instead of 40lm. It’s two AA’s now, plus they added a friggin strobe for some stupid reason. They also have the Tool AA which is the exact same thing as the IYP25, except it looks like a tool instead of an IYP.

hank's picture
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Please, please, make it autoclave-friendly.

Doctors spread diseases: