Couple of LED lights using Joule Thief circuits ...

wquiles

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You would think that given how many flashlight projects I do that I actually own a lot of lights. Actually, I own very few lights (well, to a non-flashaholic I own an "arsenal" - but in reality I only own a few lights - most are customer lights that I photograph before sending them out to their respective owners). A couple of weeks ago we lost power here where I live and it happened right at 6AM - right when we wake up to get ready for work and take the kids to school. Still pitch black, and with no power, I scramble to get several LED lights scatered throughout the house so that we can all get ready. Problem was that I did not have that many lights to start with, so I started thinking about the "need" to make more emergency lights to keep around - specially/mostly indoors, where you only need a little bit of illumination, specially lights that can stand on their tail to light up a room, bath, kitchen, etc..

I already had two "big" output lights: two of my own custom 1xD's, direct driving a P7, from a 3xAA adapter. But those are way, way too bright for a small room indoors, so I needed something with less output, and that would run for a LONG time as well. Since I recently have been playing with my own Joule Thief circuit, I decided to build a couple of lights to take advantage of the abundance of used AA cells and LOTS of new D cells (that come free with most D Mag's that I buy from Fry's, HomeDepot, etc.). I also though about making my own P60 drop-in with a super low output, for night adjusted vision, so I started working on these.

First is the P60 drop-in. I bought a "kit" from Asia for the P60, so I started looking at what emiter would work well with the smooth reflector. I started with an older P4:
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But decided to use a more efficient LED instead. Looking at my parts bin revealed a neutral white XM-L, so I reflowed it into a datiLED 8mm board:
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When I tried it on the smooth reflector, I was able to get a great beam :D
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So I soldered and epoxied the Joule Circuit on the back:
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And tried it with a few cells:
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I soldered a wire to the spring (Bat +) that comes with the kit:
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And simply (although not "pretty) used hot glue to keep everything in place - very solid, firm setup:
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The fit of the base to the reflector in these kits is horrible, so I used a thin piece of copper tape to set the focus to the right spot in a press-fit:
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And this is how it looks in the Solar Force host:
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Home made P60 drop in:
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Nice tint:
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I can use new or used CR123 cells, but since my circuit can operate down to 0.8 volts I decided to make an adapter/sleeve so that I can also use AA cells in this host:
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With an AA cell it was a tad shorter than an 18650 cell, but the springs more than make up for the difference:
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The next light uses some really old 3W LED's that I got many years ago, but that were vf-matched to 3.5-3.6 volts), so I decided to build a floody light using 3x of these LED's, each driven by its own Joule Thief circuit, everything feed from 3xAA cells (using another of my own custom 1xD's as a host). Since I wanted to re-use parts I already had, and I did not have any reflectors for these weird looking LED's, I decided to modify a home-made Mag D P7 reflector and make a sort of "dish" reflector out of it.

I started with the P7 heatsink to hollow it:
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It is hard to see in this picture, but I cut a lot of "facets" in the heatsink, going from outside towards the inside, using my very sharp PCD insert to achieve a polished effect on the Aluminum:
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Then drill and chamfer the hole for the wires on both sides:
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I then did a dry fit to see how I can place the 3x "weird" emiters. Note that I had to cut/trim their wires to give me clearance:
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In this photo you can see a little bit better the facets in the heatsink - nothing too fancy but seems effective:
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I then proceeded to glue them:
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I then carefully solder the wires:
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And since this is going to be floody and very open, I put a good dose of glow in the dark powder with 2-part slow cure (30-min) epoxy:
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I then solder each of the 3x Joule Thief circuits:
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And test it:
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Here it is running:
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Ready in the host (heatsink is a press-fit):

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I carefully cut/fitted the reflector so that it would line up over the heatsink, to provide additional "focusing" on the sides:
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Here is how it looks from the front after being turned off - notice how the heatsink reflects some of the light, as well as the cut Mag reflector:
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Of course, in raw form the image is fairly "ugly", so I planned on using a diffusing film to even out things:
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Here it is OFF:
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Here it is ON:
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And although not quite focused, here is the afterglow:
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OK, now for the last "emergency" light. I already had the floody light, so I decided I wanted one with more throw. So I decided in a neutral white MC-E, using another of my own custom 1xD's as a host, so it can be driven from a single D cell or a 3xAA adapter. First, I had to once again modify the P7 heatsink in order to facilitate installing the MC-E. Fairly easy on the mill thanks to the DRO:
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I am using a left over metal reflector for P7's that I had handy:
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So I prepared everything:
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And used the reflector to position/center the LED by eye as best as I could:
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I then solder wires:
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Wired a single Joule Thief circuit:
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Prepared the stock switch:
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Here is the finished product:
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And although not in focus, here is the afterglow:
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That is for now. By the way, guess which of these 3x my kids LOVED? Of course, the weird one with the 3x LED's and the massive afterglow of the glow powder :D

Will
 
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Mike S

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Very nice. Those turned out great.

Do you use the same components in all of your joule thief circuits regardless of which emitter is being used? Also, which power LED's perform the best?

It's interesting to see how few components are needed to boost voltage from a 1.5V cell. I have a few cheap lights which only have a transistor and an inductor, and that's it.
 

wquiles

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Yes, same circuit. I made my own boards to use this specific Zetex part (ZXLD383):
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I can change the inductor to adjust the current setpoint, but the overall current varies with the battery supply - as the battery drains the current lowers as well, down to 0.8 volts - lower than this the circuit will not work. Right now I am using the 4.7uH to 5.6 uH size of inductors to get a fairly high current level, as the max recommended value per the data sheet is 4.7uH, but the larger the core of the inductor the less saturation at the higher current levels. Still, it is all relative - this is not a high power boost circuit :D

Will
 

TriggerHappy

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Hi
Thanks for posting the circuit - all the Joule Thieves I have seen have required winding a little transformer etc - that little chip makes it so much neater!

Pete
 

wquiles

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Hi
Thanks for posting the circuit - all the Joule Thieves I have seen have required winding a little transformer etc - that little chip makes it so much neater!

Pete
Yup - the tradeoff is having to deal with surface mount parts, which could be a pain if you don't have experience with them. Pretty much everything I do is surface mount now-a-days, so it is not too bad once you have boards made.


I'm certain you could sell alot of those circuits. I would certainly buy a few; price dependent of course!
If there were enough interest I could start a proper sales thread. Email me if interested.

Will
 

^^Nova^^

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Those pcb's look good Will. What diameter are they, they look very close to a AA battery?

DatiLED made and sold some JouleTheifs a while back and they didn't last long, I am sure you could sell many of these boards.

Cheers,
Nova
 

wquiles

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Those pcb's look good Will. What diameter are they, they look very close to a AA battery?

DatiLED made and sold some JouleTheifs a while back and they didn't last long, I am sure you could sell many of these boards.

Cheers,
Nova


Thanks. I got enough emails to justify opening a formal sales thread for these. As to size and other details, I put all of that in the sales thread.

For now we can keep this thread focused on lights/projects that use these circuit boards.



Admins - I am linking to the sales thread - I hope it is allowed/permitted: Link to sales thread



Will
 
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Kestrel

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I'm very interested in trying a P60 joule thief with 2xAA in a three-cell SF body. Taking an excerpt of the data you posted in the 'hurricane lamp' thread:
  • Vin = 1.0v, Iout = 0.016A, eff = 27%
  • Vin = 2.0v, Iout = 0.120A, eff = 78%
Therefore, using two depleted AA's rather than one will be an excellent configuration IMO. There seems to be a lot of potential here. I love doing this kind of stuff with my C3's. :thumbsup:

Edit: The above data is outdated, see Will's post below.
 
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wquiles

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Kestrel,

Yes, the 2xAA configuration (or 2x D in a Mag 2D body) is awesome. I took one of my 4x CR123 bodies and used to of my home-made AA to 18650 cells and built a 2xAA equivalent, and it works great.

The only thing to note is that those higher current levels were achieved with those HUGE inductors I used in my first evaluation since that was what I was able to get my hands on. Unfortunately wiring those large inductors is a royal pain and on top of that using the large inductors leave you very little room for a P60 module, so I am now using the surface mount inductors which give me a little bit less current.
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With the much smaller surface mount 4uH inductors I am now using I am getting about 50-60mA at 1.5volts and 100-120mA at 3.0 volts, which is still very decent/effective in sucking whatever life is left out of primary cells :D

Will
 
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Kestrel

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[...] With the much smaller surface mount 4uH inductors I am now using I am getting about 50-60mA at 1.5volts and 100-120mA at 3.0 volts, which is still very decent/effective in sucking whatever life is left out of primary cells.
Ah, good, thanks for the clarification.
 

Darvis

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Will... :rock:

You truly possess some mad skills my man!!!

I have to admit, I'm super jealous of the whole machining aspect you bring to the table whilst I'm relegated to plumbing parts and tupperware for my lights...

This is great stuff!

BTW, the AVR programming is a hoot!! A few days into it and I've gotten all kinds of blinking LED madness going on here... which brings me to a question for you: I see Atmel sells some chips that have boost circuits built in, have you played with these and the PWM outputs? I wonder if they can be JT-ish if programmed right?
 

wquiles

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Thank you :eek:

Glad to hear you are enjoying the AVR stuff. It is very neat to be able to get things working fairly quickly - it is a great platform. I have not seen the Atmel chip you mention, but would love to take a look. Got a link/URL?
 

Darvis

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I was looking at the Attiny25v, but misread the min voltage requirement to be .8v when instead it's 1.8v... too many late night learning sessions on the net for me!!
 

wquiles

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This was completed recently by Drywolf


Hey Will,
Got my package today. Very professional. I'll post a pic or two of my completed thief later today.

thief_01.JPG


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3 x Nichia NSDW570GS in parallel, one driver and two x AA in parallel.
Thanks,
Frank

:)

.


I really like that!


Will
 
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wquiles

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By the way, I am planning on perhaps offering a "kit" for the next wave of boards, so that folks can have a "project" - perhaps something like a "father and son" (or daughter!) Saturday project. Or perhaps something that could/would be a good project for boy scouts, for camping, etc..

Will
 

sassaquin

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By the way, I am planning on perhaps offering a "kit" for the next wave of boards, so that folks can have a "project" - perhaps something like a "father and son" (or daughter!) Saturday project. Or perhaps something that could/would be a good project for boy scouts, for camping, etc..

Will

I am very interested in a kit.
 
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