Kame Sennin entry for Old Lumen challenge 2019 [hand made]

Big Thank You to all the contest team for the incentive to get our nose out of our PC screen and build something nice (well ... as nice as possible !)

I have several ideas for building small flashlights inspired from what i have seen or used when i was a kid here in France.

A good exemple is the little red Wonder "Pigma" that shared most of my childhood adventures (left picture) . :

(random pictures from internet)

From what i recall size is about 8 x 4.5 x 1.7 cm and it use a special small flat 4.5V battery

But there was many flashlights that shared the same design with various size from the "mini" (right picture, no reflector, about 6 x 3 x 1.5 cm, special 3V batt) to the "pieto" (about 12 x 6.5 x 2.5 cm, standart flat 4.5V batt)

So my general guidelines are :

  • small rectangular box
  • works from one or two AAA or AA
  • basic UI : on/off, maybe some dimming if i have time for that
  • floody, low lumen, low CCT
  • as much as possible i'll use what i have already lying around
  • hand wired prototype board for the driver

Depending on available time i expect this to be an iterative process with a first very basic build and further improvements if possible.

To be continued

That light reminds me of another someone made ;)

Welcome to the contest :THUMBS-UP:

I’ve thought of converting something like this several times. There a re a glut on ebay, some have coloured filters that you can flip over. Since next to no people make a rgbw light, I was tempted.
Can’t wait to see what you come up with! :slight_smile:

I like it, Good choice. Etsy.com has old vintage flashlights like the one you picked.
Our childhood flashlights hold a special place in our Hearts. :slight_smile:

Thank you :)

I don't intend to modify an existing torch but to build something that remind me of the ones i talked about in the OP, that beeing said and after seeing what CRX did with the same "spirit"i am now wondering why i din't just shut up ! So, please, don't put too much expectations on this build ;)

Run 1, 28 nov. Keeping it simple

Not sure where i am going exactly, so mostly "thinking with my hands" on a quick and durty prototype

  • minimal aluminum/wood case.
  • bare 5mm led
  • joule-thief type boost driver

As a starting point i used a piece of U extrude aluminum that i found some time ago in the metal trash bin.

Because the edges were very rough and somewhat torn, i sanded them before anything else.

Then i scavenged a piece of plywood from an other bin and sanded it to fit exactly inside the U.

That beeing done i started to remove some of the wood (hand saw and chisel) to make room for the other parts.

I need to remove more wood to make room for the battery without thining the whole width but 'ill do that tomorow because i want to use the dremel and it is too noisy for now (22h30 here)

Random thoughts :

  • even with crapy scavenged parts it looks better than i thought it will (low expectations helping ;) )
  • why not to carve the AAA battery holder into the wood ? (might be too late so i'll have to use an other wood block)
  • my first idea was to poke the bare led into a "conical reflector" shaped hole in the wood but this will require some better/harder wood

Good start :+1:
A bit sanding & polish when it’s all together can totally transform the look though I can see the potential now.
I like scavenging parts too.

:+1:

subscribed. Nice build idea :+1:

Another terrific home made light in the making. I know if I tried to do what you are doing it woodn’t work. :person_facepalming:

Looks like a this style of a host would be nice for LedLink Athena, 45 or 60 mm version:
https://www.ledlink-optics.com/2018/05/31/v-cut-reflector-2-2-2/

But you’re clearly going in a different direction. :slight_smile:

Yes! Eye of Sekhmet, that’s what you meant, right? :stuck_out_tongue:

Yes, that has been an inspiration for a few builds :wink:

Run 1, 29 nov. Joule thief

After writing yesterday's post i started to think about several modifications/improvements in the way i might use the wood block but still have some unanswered question (mainly about the on/off switch and battery compartment) so i decided to work on the driver instead.

Minimal boost driver recipe :

Take a length of enameled copper wire, the smallest toroid ferrite core you can get, one of these very nice 5mm high CRI 3400K led rngwn is selling plus a (small) npn transistor (PMBT2222 here) and a (even smaller) 1k resistor. Don't forget your schematic !

Assemble the parts on a piece of prototype PCB and, after verifying that everything is ok, switch the power on.

More about the joule thief after dinner ;)

Sweet idea! Great work there using the hands to think it out. :smiley:

:+1:

Thank you :)

The dinner was short but i had to do a lot of measurment so i am back only now !

I know that's a lot of numbers but i'm still searching a way to display them in a clear and nice graph (anyone knows how to have several secondary axis on a graph with Libreoffice Calc ?)

At first i measured a led alone, varying the curent and measuring the led voltage and light output and calculating the led efficiency :

Supply curent
(mA)
Supply Voltage (V) Supply Power (mW) Light output (lm) Led Efficiency
(lm/W)
1,0 2,59 2,7 0,3 129
2,0 2,62 5,3 0,7 128
3,0 2,64 7,9 1,0 126
4,1 2,66 10,8 1,3 125
5,0 2,68 13,4 1,6 123
6,0 2,69 16,2 2,0 122
8,0 2,72 21,8 2,6 119
10,0 2,74 27,5 3,2 116
12,0 2,76 33,1 3,8 114
15,0 2,79 42,0 4,6 111
20,0 2,84 56,8 6,0 106
25,0 2,88 72,0 7,3 102

Then i did the same kind of measurements on the driver + led and used the (roughly interpolated) led efficiency calculated in the previous table in order to obtain the driver efficiency :

Supply Voltage (V) Supply curent
(mA)
Supply Power (mW) Light output (lm) Total Efficiency
(lm/W)
Led Efficiency
(lm/W)
Driver Efficiency
( %)
0,60 10,1 6,1 0,4 65 128 51
0,70 15,6 10,9 0,7 67 128 52
0,80 22,7 18,2 1,2 69 125 55
0,90 25,5 22,9 1,6 68 122 55
1,00 27,9 27,9 1,9 67 122 55
1,10 29,8 32,7 2,2 66 120 55
1,20 31,4 37,7 2,5 65 119 55
1,30 32,7 42,5 2,7 64 118 54
1,40 33,7 47,1 3,0 64 117 54
1,50 34,8 52,4 3,3 63 116 54
1,60 38,1 60,8 3,8 63 114 55

The efficiency is not too bad for a "wet finger" type of design but the light output is a bit low for my taste.

For comparison here are a few values that i measured on a warm white Sofirn C01 :

Supply Voltage (V) Supply curent
(mA)
Supply Power (mW) Light output
(lm)
Total Efficiency
(lm/W)
1.0 38 38 3.0 80
1,5 54 81 5,5 68

So now i have two options :

1) Try to optimize the joule thief driver for more output (find a better transistor, test various parameter changes for the transformer)

2) Use a more conventional (and predictable) regulated boost driver

Well it's 03:15 so the only real option right now is to go to bed ...

Edit : corrected a few errors in the driver + led table

2nd edit : C01 data with more accurate test

I really like that driver out of a few simple items. :slight_smile:

Run 1, 1 Dec. More tests

So i was balancing between trying to improve the joule thief or going for something more conventional ... and i eventually decided to keep the JT for this prototype.

Several, reasons :

  • it's cool ;)
  • i like to tinker with new things and i don't know that type of converter very much
  • i usually prefer a regulated output on my flashlights but the "less volts, less output" works well for a small vampyr light
  • there is plenty of time for improvements and tests before the end of the contest and i'll still be able to change my mind later and go with an other driver if i feel like it.

While i intent to do a lot of measurements on the driver for each modification i have to improve my test setup !

One thing i went through friday evening while doing the first tests set was that it was teddious to read the display of the two multimeters and the luxmeter because they were not leaning at the same angle so i improvised a "deluxe foldable measuring stand"

Ok let's work now !

I expected to be able to use a breadboard with traditional "through hole" component for easier components changes but the result was not very good (unstable measurements caused by bad connections) so i had to ruin the nice prototype with a lot of soldering/desoldering.

An other problem i met was i had no good way to fasten the protype to my integration sphere which caused some variations in the measured light output so i eventually soldered the led on his own board with a long wire running from the driver and taped the led board to the sphere so i was able to work on the driver without disturbing the led position.

Eventually i was able to obtain stable and repeatable readings and went through many tests series

The following picture shows the final setup :

Not much else to show for now as i tested several transformer configurations along with several resistor value during the weekend but this is still a work in progress and i don't want to frighten everyone whith pages full of numbers !

Run 1, 4 Dec. Still testing

Just a quick update as i don't have anything new to show but a lot of boring tables full of numbers, a poor abused prototype and some weird 3 or 4 legged toroids

I am still working (maybe 20 hours total now) on the joule thief driver, trying to obtain the right tradeoff between output and efficiency, and i feel that i have gone as far as i could with the PMBT2222 so i have ordered a few other references that i expect to be better in that application (mainly higher gain and lower Vce-sat) and hope to receive them before the weekend !

Nice effort so far!