My DIY Joule Thief Hurricane Lamp Project: Lots of pics!

Darvis

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All,

I wanted to sit down and give a little back to CPF since it's been so good to me over the past few years; I have learned much here from a lot of real smart folks!!

I have long been dying to dabble in a bit of circuit building, so naturally, I thought I'd start with a pretty easy and fun circuit that we all may know and love: The Joule thief… yes, It's been discussed here before, and in many other places, so not something really new, but:

The twist is that I took the concept and made it into a AA emergency (hurricane) lamp using parts found in basically any electronics and hardware store (I shopped at the well known major chains). I thought this would be a fun and practical project for the family.

For those that are new to this, like me, the Joule thief is a very simple circuit that essentially boosts the voltage of any AA battery (especially ones that appear to be dead from a remote control or kid's toy) so that It can power a white or blue (or any) LED that requires a forward voltage (vf) of about 3.3 volts. I did not know this coming into the hobby, but diodes (LEDs) have very specific voltage requirements and will not run when the voltage is too low, hence the need to boost the voltage source.

So, parts, here we go (total cost for this project, btw, assuming you have the tools: ~10-15 bucks)

1.25 inch PVC repair coupler (bigger if you want to use D batteries)

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5 gallon bucket lid (for caps and the circuit board) the plastic that these are made out of is super pliable and easy to cut, but is also quite sturdy; a great combo for all sorts of parts.

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One switch. I highly recommend the Gardner Bender model GSW-24 push button lamp switch that I got from the major chain hardware retailer. I tried cheaper toggles and they were terrible. These puppies are way over-engineered for this project and come with pre-wired leads. Well worth the 4 bucks.

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And here's a look down the tube at how the switch mounts on the inside:

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Some phone wire or cat 3 wire, or any thin gauge solid wire… You'll need this for winding your coil and all of the rest of the leads

One 2N 3904 transistor (or 4401). Buy a pack of these as the little leads are fussy and I snapped more than a few off, be careful with these!! I mount them and leave them alone!!!

One 1k ohm resistor

One Ferrite Bead for making the coil

One white or blue led with a vf of 3-3.5 volts

AA battery holder

Drill and bits, wire strippers, soldering iron and solder, pliers, wire nippers, electrical tape and/or shrink tubing (found at any hobby or electronics store)

So first things first, I drill a 3/8" hole in the side of the PVC coupler for mounting the switch. Your bit size needs will vary depending on which switch you buy/prefer; but for the model above, this bit works with just a bit of reaming.

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Next, I cut some bucket lid to fit inside the coupler ends to make the bottom and top caps

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Using a 3/16" drill bit, I drill the Led hole in the upper cap, nearest the switch (a 5mm LED will fit perfectly through this and hold nice and tight with no glue) The skirt on the bottom of the LED will keep it perfectly set in the hole and will not allow it to pop through. You'll see some better pics of this in a bit.

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That prep done, I then make the "circuit board" using another little square piece of lid and a 1/16" drill bit. Not rocket science and you can drill this out any way you like. You'll see this in a bit.

That prep out of the way, I then go to work on the circuit. Now I'm not going to diagram out the circuit as there is tons of info on the internet about how to craft this little gem and I think half to fun is researching this; but I'll add some lessons learned here to make things a bit easier. That said, look up "joule thief" and go to the link for the "evil mad scientists." This particular video was all I really needed and they also have a very detailed toroid winding tutorial with great, detailed pictures.

First, I highly recommend using a breadboard to get it right the first time; it will save you tons of headaches!!!!
Then, one must wrap the coil, and this is the trickiest part… I have found via trial and error that one needs at least 10 turns to get the right voltage boost. I went with smaller coils at first with fewer wraps and had dim LEDs, took me a while, but I came to this conclusion after some frustrating attempts on the breadboard. Do this part right!!! It pays off big in the end. After you are done, wrap that puppy in some electrical tape because if the wires come loose and cross, it will not work!!!

Next, take your bread board circuit and mount everything up on the board; make sure you leave leads for the battery and LED. I test this once before putting it all together. Here's that circuit board I mentioned earlier… and a bottom view of the LED mounted through the hole. No shots of this, but all connections are soldered in the back of the board.

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Solder it all together in the light. The switch is wired between the negative lead from the battery and the board. The positive lead is wired right to the battery holder. I typically use red for positive and black for negative to keep it all straight. All the extra wire also helps keep things from bouncing around inside. Make sure to put your shrink tubing on first!!! But no worries if you forget, it's nothing that can't be fixed with some electrical tape.

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It's a tight fit! Just sort of stuff it all in there and use care when shoving the coil on down in. I actually try very hard to kind of make things fit nicely and not twist the leads. Wrapping the whole circuit board up in electrical tape helps a lot, you'll just have to fiddle with it.

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Here's a view of the battery/bottom end:

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Once it's all together, click and enjoy!!!

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I used PVC end caps at first on the top, but quickly settled on the end cap that comes with the coupler and bucket lid piece as the recessed LED works better… no annoying shine in the eyes since this thing really needs to ceiling bounce anyway.

Another thing is that some will say the Joule Thief will take a AA down to .30 volts, but I only get to about .70v- Might be the smallish coil, but I'm not complaining as this thing seems to run forever off a fresh AA.

My eyeball integrated sphere calculations put this powerhouse at about 5-10 lumens, surprisingly bright in pitch black with dark adapted eyes. Heat from the LED (HA!) is not an issue and things got real kooky when I built the big "triple" which I actually recommend one shoots for. It's really the best in terms of output and is super easy to do, just wire three LEDs in parallel, no magic needed. I drilled a triangle hole pattern and put it all together.

Build your first light as a single to get it right (you'll want to build lots of these once you get going anyway) then build the triple for real world use. The output difference is noticeable and any beam artifacts from the cheap LEDs tend to go away with the triple.

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I also ordered some higher quality higher output LEDs online and will see what they can do…

My kids love these things and decorate them with all kinds of stickers and such, I'm going figure out how to add some GITD epoxy to mine for that "find it in the night" feature. Hope you all enjoy them as much as I do. Please feel free to PM me with any questions or if I need to clarify anything in this thread.

Please also post pictures of your builds (if you build that is); I'm eager to see what other mods/ideas people come up with.

Darvis

Update: A couple of things I've tried in the last day since this post...

Got some real nice basic ferrite beads from a website called kits and parts; so if you're wondering where to source these, this would be the place. I went with the FT50-43 beads and was able to get 9-10 wraps on the toroid. All brightness was the same vs. my other beads and a straight 123A

Also received and tried some great 15 and 30 degree 5mm LEDS that were 18,000 MCD from Super Bright LEDs. the 15 degree ones are a little blue, but not too bad. Going to mount the 30 degree ones in the triple and see how it goes, but these are definitely the brightest I've tried yet and worth getting for this project
 
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Darvis

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Mods: I should have posted this in the homemade flashlight section, sorry about that. Please move as necessary.

Regards,
Darvis

EDIT: Thanks!!!
 
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Darvis

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That's a nice little light. You've encouraged me to try my hand at making my own Joule Thief lights.

Thanks, It's come in handy more than a few times over the last week. Let me know if the steps above help/work for you and if I need to clarify or elaborate on anything. I'm interested to see what you come up with, so post it here when you're done and good luck!!
 

bstrickler

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Darvis

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You can actually make a Joule thief with only 2 components now.

http://www.mouser.com/Search/Produc...TAvirtualkey52230000virtualkey522-ZXSC380FHTA
http://www.mouser.com/ProductDetail...=sGAEpiMZZMsVJzu5wKIZCbTeDXLH31lgzP16QE4Fnjg=

You might need a power LED, though, because it's putting out about 50 mA at 1v input.

I'm definitely ordering a couple of those next time I order from mouser, and havin a little fun.

~Brian

Now that is way cool. If I understand the spec sheet correctly, it looks like mA can be set via inductor selection? That would really make things easy, though, just buy a pre-made inductor and this and go to town!! Thanks for the heads up, I think I'm going to buy a few myself and play around with them.
 

bstrickler

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Now that is way cool. If I understand the spec sheet correctly, it looks like mA can be set via inductor selection? That would really make things easy, though, just buy a pre-made inductor and this and go to town!! Thanks for the heads up, I think I'm going to buy a few myself and play around with them.


Yep, just choose a 22, 47, 68, or 100 microhenry coil, and you'll have customizeable output. Next thing to do would be to make a 3-level twisty (22,47,100 microhenry, since 68 is almost the same output as 47). 3 coils, 1 microprocessor, and the ZXSC380. Sounds like a challenge I'll have to try!
 

Darvis

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So, if I don't want to poof my 20mah LED at 1.5 volts or less, which inductor would I get..? not sure I fully understand the spec sheets. I think it would be 47mh, but not 100% sure on that.
 

Darvis

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Page 6 shows this as the output at 1.5v

100uh=19ma
68uh= 16ma
47uh=15ma
22uh=10.5ma

~Brian

Thanks Brian, I thought that's what I read, but doubted what I saw.. Appreciate the info, I'm going to try me a two part joule thief!!
 

flatline

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You can actually make a Joule thief with only 2 components now.

http://www.mouser.com/Search/Produc...TAvirtualkey52230000virtualkey522-ZXSC380FHTA
http://www.mouser.com/ProductDetail...=sGAEpiMZZMsVJzu5wKIZCbTeDXLH31lgzP16QE4Fnjg=

You might need a power LED, though, because it's putting out about 50 mA at 1v input.

I'm definitely ordering a couple of those next time I order from mouser, and havin a little fun.

~Brian

For those of us who are new to this, could you give some explanation on how to use these two components to make a joulethief? I think I understand what I'm reading, but I'm not confident.

Thanks!

--flatline
 

Darvis

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Flatline,

The inductors act as the coil and contral the mA output that drives the LED. The microprocessor eliminates the need for both the transistor and resistor (and a lot of the wiring).
 

Justin Case

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Maybe the one main downside to using the ZXSC380 is the datasheet's 0.8V min input voltage spec. A basic Joule Thief can run with around 0.6V input (possibly even lower than that), although the output is probably quite low. However, if you can feed the JT with 0.7V input, you can get some useful light.
 
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