DIY Flashlight kit

[kalel]

There's a simple DIY Flashlight kit for about $1.7, called:

"DIY FLA-1 Simple Flashlight Circuit Board Electronic Kit"

Basically, there's a little case, a little PCB and a few components (pretty neat for the price, that a case is included).

There are some "practice" pads, which is interesting:



I'd like to ask you two questions:

1 - How the voltage boost works (battery 1.5 to ~3 for the LED) - I only see an inductor, a resistor, and what looks like a transistor (note that on Banggood I don't see a parts list), I thought it might be a "Joule Thief" type circuit. But, the inductor has 2 pins - I don't see a center tap. There are usually 4 pin chips, e.g. QX5252 for solar lights which work with a single added inductor, which determines the current, but the kit has a 3 pin part, whatever the part may be exactly. Perhaps there are 3 pin variants of similar ICs. There's a marking "161007" on the PCB, but I wasn't able to find what that might be.

2 - Any interesting modifications that could be made, perhaps using the "practice" pads on the PCB. One I can think of is maybe adding a small li-po battery and minimal amount of necessary components, but the micro-USB port would require a new hole in the case. I'm not sure if the flashlight would be used so frequently that a rechargeable lithium is an interesting upgrade.

Considering just the parts (case, a nice on/off switch, built-in battery holder) and the price it seems like an interesting thing to get. What are your thoughts about this simple kit?

[Gary350z]

The transistor looking device is a LED driver IC, part number YX8115. See the following links.

FLA-1 Simple Flashlight Kit DIY Module 1.5V 55x35x11.5mm DIY Kit:
http://www.icstation.com/simple-flashlight-module-55x35x115mm-kits-p-11877.html

YX8115 datasheet:
http://www.datasheetcafe.com/yx8115-datasheet-pdf-led-driver/

YX8115 information:
https://www.google.com/search?q=YX8115&rls=com.microsoft:en-US:IE-ContextMenu&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwi6sIunoIjVAhXGVyYKHR-6CesQsAQIJw&biw=1336&bih=755

[kalel]

The transistor looking device is a LED driver IC, part number YX8115. See the following links.

FLA-1 Simple Flashlight Kit DIY Module 1.5V 55x35x11.5mm DIY Kit:
http://www.icstation.com/simple-flashlight-module-55x35x115mm-kits-p-11877.html

YX8115 datasheet:
http://www.datasheetcafe.com/yx8115-datasheet-pdf-led-driver/

YX8115 information:
https://www.google.com/search?q=YX8115&rls=com.microsoft:en-US:IE-ContextMenu&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwi6sIunoIjVAhXGVyYKHR-6CesQsAQIJw&biw=1336&bih=755

Thanks - that explains everything. Seems like a nice little chip (I assume it's the simplest way to step up voltage for the purpose).

[Red Squirrel]

On sort of similar subject, I've found that an 18650 cell fits perfectly in a piece of 3/4" copper pipe.  Could make an interesting use for building a custom flashlight.  Was just a total random thing I thought of checking.

[kalel]

On sort of similar subject, I've found that an 18650 cell fits perfectly in a piece of 3/4" copper pipe.  Could make an interesting use for building a custom flashlight.  Was just a total random thing I thought of checking.

It's always nice to get a proper case for a project. And since that's a copper pipe, it can provide some cooling (I mean heat dissipation) too? Perhaps a more powerful LED can then be used, with slight heat-sinking connected to the pipe somehow (might be a challenge to find the perfect shape).

[kalel]

I've received the kit from Banggood. Now I can also see it on AliExpress. It goes for around $2.

Here's my experience and some screenshots.

It uses an IC that simplifies the voltage boost from AAA. So only one inductor is needed (vs two inductors or a coil with two windings if using a Joule Thief). I'm not sure how different they would be in practice beside that one part.

Here are the parts that you get (they arrive in the case):





Zoomed in:


The inductor is covered by some heat-shrink. Here are the values of measured components.

Inductor:


Resistors:



There's only one resistor marked on the PCB, so two values might be available for experimentation, and one extra piece of each for redundancy.

Here is the PCB:



I'm not sure what the practice pins holes are intended for exactly.
Assembly is relatively simple, as everything is marked on the PCB.

Here is the result:



I didn't properly support the switch, which now might be easier with some glue. The LED is working and in a completely dark room it does bring some light. It will probably work until a relatively low battery voltage, by measuring an old battery it stopped working at around 0.8v, but I haven't tested it on a suitable supply. The brightness is definitely quite low but we can't expect too much from one 10mm LED. The beam pattern is focused. Runtime has not been tested, but is likely long enough with a proper battery.

[DGfromMTL]

Hi newbie electronics tinkerer and fan of mr. jones, big clive, here.

I just bought a couple of these kits on ebay for $1.80 ea. - with the intention of trying to work a joule thief into the circuit so it can be a flashlight to use old spent alkalines with. Given the cut little kit comes with a litle section of protoboard "practice area" I should have room add the transistor, a toroid coil and a resistor.

https://www.ebay.ca/itm/DIY-Kits-FLA-1-Simple-Flashlight-Module-1-5V-LED-Light-Lamp-Module/362135593679

I've sucessfully built a joule thief before (use it to light a little LED strip) - but I'm not sure where to start to rework this kit into a joule thief configuration.

I assume I won't need either the YX8115 driver chip (Looks like a transistor) or the 47uH inductor.

Looking for suggestions on how I could appraoch re-jigging the circuit as a joule thief powered  light?  I appears at first glance I should be able to simply replace the coil, chip and maybe a resitor.

Any help, pointers greatly appreciated.

Cheers

Dave

[soubitos]

If anyone is interested, i recently made 150 pcs pcb for a joule thief night light which i will be selling shortly (I still miss the capacitors needed, damn POST).....

[phil from seattle]

It would be great if you could characterize the switcher IC. At least figure out how low a voltage it will run on.  You may find that does the same as a JT.

[kalel]

It would be great if you could characterize the switcher IC. At least figure out how low a voltage it will run on.  You may find that does the same as a JT.

This lamp kit is already a "kind of" joule thief (as in a basic step up converter). For me, this lamp did work on low charge "run out" batteries (although I think it was visibly dimmer than a fully charged battery). I did not characterize the exact voltage where it turns off (lacking the proper supply), but it seemed to work down to about 0.8v (measuring the battery while the lamp was running).

The characteristics are here:
http://www.datasheetcafe.com/yx8115-datasheet-pdf-led-driver/

Which are similar to my measurements:

Feature
1. Low operating voltage : 0.9 ~ 1.5V
2. Low start-up voltage : 0.9V
3. High efficiency: 80% or more

Also, it seems you can get up to 5 LEDs, from that page.

What I would recommend (if you have a couple), is that you simply build one as is, and then check if it satisfies your requirements. After building that one, if you still want to build a Joule Thief either for fun or to get improved low voltage performance, you will have something to compare it with (e.g. does it work better in practice than the existing circuit on low voltage).

The interesting part is that some of these ICs are even called "Joule Thief IC" by the Chinese creators.

[soubitos]

YX8018 is a similar ic for garden solar lights.. i found this interesting page about them https://dzrmo.wordpress.com/2012/05/29/garden-light/

in the photo from that page which i also attach here you can see the datasheet "internal view"

[DGfromMTL]

Yes, that is a great suggestion to compare one built to spec and then a modified one, given that chip spec is has a low start-up voltage : 0.9V
I think I'll breadboard a bit to see how different coils / winding will affect the output with YX8115 as well.

Thanks

[kalel]

Yes, that is a great suggestion to compare one built to spec and then a modified one, given that chip spec is has a low start-up voltage : 0.9V
I think I'll breadboard a bit to see how different coils / winding will affect the output with YX8115 as well.

Thanks

In case you like these ICs, they are fairly cheap from Aliexpress. But I (think) it might be possible to get an even lower voltage from a custom Joule Thief, but I'm not sure about the exact calculations, in fact, my first Joule Thief was following BigClive's video, and did not follow any exact calculations or winding length - in fact I did not even have proper enameled wire for the windings, so I used some cheap stranded copper coated wire. It still worked well (visually), but from what I understand efficiency might depend on getting these parameters to optimal values. There might be some calculators already available online, since it is a famous circuit.

One other thing to note, which you may know already, since the most basic Joule Thief gives only pulsed voltage, color changing LEDs will not work properly (perhaps also some blinking LEDs or other specialized LEDs). This is solved by adding a diode and a small capacitor (to stabilize the voltage somewhat). These things could be fun to measure with a scope (and no mains issues to destroy a scope since this is battery powered) for those that have one. 

[DGfromMTL]

Thanks,

One other thing to note, which you may know already, since the most basic Joule Thief gives only pulsed voltage, color changing LEDs will not work properly (perhaps also some blinking LEDs or other specialized LEDs). This is solved by adding a diode and a small capacitor (to stabilize the voltage somewhat). These things could be fun to measure with a scope (and no mains issues to destroy a scope since this is battery powered) for those that have one.

Well, I did happen to buy myself an old $50 analog oscilloscope for my birthday   
( been looking for awhile per the Dave Jones videos)  - so, this project would be a good use for it.
(just been goofing around with lissajous stuff so far)

In case you like these ICs, they are fairly cheap from Aliexpress.

Looks like there are a number of similar chips on Aliexpress & ebay , I searched for "LED Lawn chip" and found this one: YX8018  seems rather common..

Just noticed the englsh datasheet for YX8018  soubitos kindly posted above..

[soubitos]

What got me involved with joule thieves in the first place was a chinese YX or QX chip, similar to those already mentioned but charging a LITHIUM battery instead of NiCd or NiMH. I had it in my shopping list for quite some time and by the time i was ready to order it, it was no more! I searched for it but didnt find it so i started looking around for other means to do what i wanted....  i built several joule thieves and had several YX chips from no more working garden lights to experiment with.... It is quite exiting to light up an LED or two with an otherwise "empty" battery but the result is not "bright" enough for me... so i experimented more... the joule thief night light i mentioned above uses a single common axial inductor which makes it very cheap and simple to make is originally designed to light two LEDs. I experimented with various LEDs available to me and the best choice so far is a 3W epistar led, intended for flashlights as far as i can tell.... BUT especially this one, although very bright and long lasting with the JT, brings out the main problem of the design... it dims out gradually and although it is lit after several days, it is nothing but a spot in the dark than a bright light source it was when the battery had some more juice to it in the beggining..... it is better than the 2 3-5mm LEDs though at least those i tested and there is an endless variety of LEDs out there to test it with... It is a very nice circuit to experiment with and learn from it quite a lot of aspects of using transistors and inductors etc...

These issues mentioned above lead me to change the original design in another project... with small changes i am using a small solar panel to charge a lithium battery instead of an AA-AAA NiCd-NiMH and using a beefier transistor in the output i am lighting a 12V Led Strip... i even managed to light the LEDs from a flood light (says 10W, i think for like 5) but after 10-15minutes the transistor is very hot...

So, joule thieves are very interesting and they come in many forms and shapes as it seems...
The most important though for me is they are fun to experiment with and they can be used in a lot of applications

[IanMacdonald]

I could suggest some of the smaller COB LEDs for making work lights. They give a more even light. The single LEDs are good for torches that need to throw light, but for a work light I'd suggest the smaller COB units. Advantage is wide even illumination.
 
Ranpo Lighting have the 3W types at ten for under £2. No kidding.

They are 3, 5 or 7 chips in series so need higher voltages, but no problem for driving from 6v or whatever if you use a step-up.  If run at full power they need a heatsink, but would take 1W or so as is for a small light. 

If you use lithium, take heed of the safety issues of course. Charge balancing/protection board, regulated charger and care over wiring - you don't want a short.

Here's my effort using 3 of the 3W COBs in a surplus halogen flood housing.