Building a LED light...

Hello,
im new here. my name is andrew, and i come from the LED museum (i love that place, it was what made me find CPF). i am building a little LED torch using the Joule Theif Circuit by Clive ???. it will suck a battery down to 0.35v before conking out. at this point, you might as well do this: *battery symbol* /ubbthreads/images/graemlins/xyxgun.gif /ubbthreads/images/graemlins/naughty.gif. if there is any market for these, i will sell the little beggars in small cases. ill post images soon if :
A: i can find somewhere that will host them for free or
B: someone will host them for me.
maybe the price will be for $12 american ex shipping. possibly a bulk discount. they will come in WHITE, <font color="blue">BLUE</font>, <font color="red">RED</font>, <font color="yellow">YELLOW</font>, <font color="green">GREEN</font> and possibly <font color="purple">PURPLE</font>. for White/Purple, probably $12, for red, yellow and green $8 and for blue $10.

i appreciate your feedback,

Neg2LED

Howdy Andrew,

I, for one, think this is a neat idea. It's a fun (and in some cases useful) circuit that many would like but don't have the skills to cobble one up. You'd be providing an excellent service. Even though I've made a few in my time, I'd no doubt buy several from you at the sort of prices you expect myself.

I think, however, that you should make a few (if you haven't already) before you make too many plans. While simple in parts count, they are not trivial to build and get good performance from.

I can't offer to help you post photos, I haven't sorted that out yet, but I'm sure some other member out there can?

Anyway, welcome to CPF. Consider me (and I think a bunch of others) as potential customers when you get this together.

Doug Owen

Hi Neg2LED and welcome to the forums. That is a great and simple little circuit. I'm sure quite a few of us have built it in the past and probably the most fiddly thing is winding that flyback inductor coil. The original circuit had a couple of capacitors and a zener diode in it. Those extra components even out the spikes and makes the LED shine much better. Of course that makes it a little too large to stuff in to the PR bulb base. (Do a search for "regulated SatCure").

The sad thing is that this circuit really isn't all that efficient and not much good for driving more than a couple of 5mm LEDs. There are better and easier to build circuits available. I'm not entirely sure that $12 is a price that people are willing to pay for such output, though I'm sure it is justified for the amount of work that goes in to winding the coil. It is really little more than a hobby circuit.

OTOH, Doug Owen is a highly respected person on these forums with lots of experience in electronics. If he is willing to pay $12 for one, I'm sure he has justified it.

BTW, these things will only run to 0.35V if it has been left running. They need at least 0.7V to start.

[ QUOTE ]
Steelwolf said:
OTOH, Doug Owen is a highly respected person on these forums with lots of experience in electronics. If he is willing to pay $12 for one, I'm sure he has justified it.

BTW, these things will only run to 0.35V if it has been left running. They need at least 0.7V to start.

[/ QUOTE ]

Wow, you must have me confused for two other guys.....

Must be all that sun down under...you really ought to get into the shade from time to time.

Yes, I agree, in the 'bang for the buck' area such lights are lame indeed. However, there is a fairly constant fascination with 'draining a weak cell dry' around here. And there's a lot of folks that love to play that aren't up to cobbling their own JT together. It's my judgement (scary as that is) that a number would 'buy in' at the price specified. I'd go for a few myself (even though I've built a few JTs myself) as I'm sure others would that could/have made their own.

Then again, I'm still in a bit of shock at what CPFers paid for the 'Milky Candle', which after all started out life as just such an attempt to drain 123 cells dry.

I see *low cost* construction of such things as a great service to CPF, a way of promoting the technology. I hope our new found friend 'goes for it'.

And you're spot on about the necessary start up voltage. I did get a few to start a *small bit* under .7 but in general it needs to be running (so most of the transistor drive comes from transformer action rather than the battery). Once running, they can drain 'em right down for sure (even if the efficiency isn't much to be proud of).

Doug Owen

[ QUOTE ]
Wow, you must have me confused for two other guys.....

[/ QUOTE ] Yeah... /ubbthreads/images/graemlins/grin.gif How many Dougs do we have on the forums now? /ubbthreads/images/graemlins/grin.gif

[ QUOTE ]
Must be all that sun down under...you really ought to get into the shade from time to time.

[/ QUOTE ] Talk about sun! It's supposed to be mid autumn, but we have been having 30 degC days! /ubbthreads/images/graemlins/smile.gif

Steelwolf: you are in perth? Kool! im in Melbourne. not that efficient? who cares? for one thing, on a completely full battery the thing will light continously for a week or more, so it might make for a reasonable wall avoidance light running full time. and once your AA/AAA flashlight poops out, this thing will munch up the battery and get you about another 3 hours at the least from a battery thats down to a volt. many FLs (like the multi-aa ones with Luxeons) stop juicing the battery at 1 volt, so the 'it only starts down to 0.7v' doesnt matter much especially if you keep it on for a long period. FINALLY, a reason to NOT throw out the batteries from your mini-mag mod....

Doug Owen: i can offer these so cheap because i am in australia. the conversion factor is working well. ill list the wavelength of the leds i will be putting in the JTs....
<font color="red">Red - 640nm Peak</font>
<font color="green">Green - unknown NM, 14,000mcd</font>
White - Unknown NM, 8000Mcd, Very slight (nearly unnoticable) blue tint, GaInN Chemistry (isnt that green?)
<font color="blue">Blue - Peak 475nm, 8000mcd</font>
<font color="yellow">Yellow - 6,500mcd, unknown NM, marked Amber Yellow</font>
for <font color="purple">Violet</font> or any other colour, supply your own LED.

Updated Prices:
Green/White: $12USD
Blue/Red/Yellow: $10USD
BYO Led: $7

P.S. i may be able to lower the price even more by buying LEDs from LSdiodes.com, as the most expensive part for me is the LED. my local electronics store sells extremely expensive leds......

P.P.S notice that because these are hand-made, no two JTs will be exactly the same, after all each coil is different!

/ubbthreads/images/graemlins/wink.gif

For hosting pics, check out Logicnerd411's site. /ubbthreads/images/graemlins/grin.gif CPF pic hosting .

Have fun! /ubbthreads/images/graemlins/grin.gif

Check out one of the Chinese LED sellers like BestHongkong who is advertising on this forum - I bought 100 white LEDs from him for like 20 bucks and they are very nice and consistent.

Klaus

WOAH! cheapy! thanks for the tip /ubbthreads/images/graemlins/wink.gif

[ QUOTE ]
Steelwolf said:
[ QUOTE ]
Wow, you must have me confused for two other guys.....

[/ QUOTE ] Yeah... /ubbthreads/images/graemlins/grin.gif How many Dougs do we have on the forums now? /ubbthreads/images/graemlins/grin.gif

[/ QUOTE ]

I suspect the most common answer is 'too many'.....

More to the point, how many of us are using our real names when we come to town?

[ QUOTE ]
Must be all that sun down under...you really ought to get into the shade from time to time.

[/ QUOTE ] Talk about sun! It's supposed to be mid autumn, but we have been having 30 degC days!

[/ QUOTE ]

Yipes, that's hot for fall.....

And for those not in the know, you Aussies get 'hotter' sun. That is the summer sun is higher in the sky, the illumination more direct and perpendicular to the ground. Makes the Aussies the world leaders in skin cancers. OTHO, you've got all those unique animals like them big hopping rats with pouches in their tummies....

Doug Owen

[ QUOTE ]
Neg2LED said:

White - Unknown NM, 8000Mcd, Very slight (nearly unnoticable) blue tint, GaInN Chemistry (isnt that green?)

Updated Prices:
Green/White: $12USD
Blue/Red/Yellow: $10USD
BYO Led: $7

[/ QUOTE ]

Actually, the base LED is blue. It has to be, since you can only 'pump' phosphors to put out lower energy (longer wavelength) light. That is you can't make blue light from green, but you can the other way about. They tend to look green since you're really looking at the phosphor which completely covers the LED die. Not that it really matters to the end user of course.

The 'supply your own LED' version interests me most (I have a few odd LEDs lying about......), but 'ready to go' is probably the call for most? Sounds like Hong Kong LEDs are the call for you? I too highly recommend them for the cost conscious.

I recommend Chi Wing on EBay

Doug Owen

ah, yes, Chi Wing..... i saw that place a while ago, looks like i'll be making my PayPal do some magic /ubbthreads/images/graemlins/wink.gif. now i need a place that will sell me resistors, enameled wire, transistors, and ferrite cores in packs of 50 /ubbthreads/images/graemlins/smile.gif. ill probably only make about 50 of these, unless people ask for more. perhaps due to Chi Wing pricing i may be able to get some more exotic LEDs for these things, by special order in lots of ten only i guess. possibly smaller quantities if you are prepared to pay White LED pricing...

[ QUOTE ]
More to the point, how many of us are using our real names when we come to town?

[/ QUOTE ] No idea. Are you looking at this as a bad thing? FWIW, I've been Steelwolf since I joined my first forum all those years ago. Think it might be impossible to change now. /ubbthreads/images/graemlins/tongue.gif Interestingly, it was because my own name (Jeffrey) had already been taken up in that particular forum and I had this pseudonymn from my on-line gaming. Heck. Why not. /ubbthreads/images/graemlins/smile.gif

And that sun! I can't believe how many extra skin spots I got since moving here. Got to get them checked out soon. Definitely don't want skin cancer.

BTW, did you know that "Kangaroo" was the local aboriginal's expression for "Haven't the foggiest idea what you're talking about, mate". Of course the settler's got it all wrong... /ubbthreads/images/graemlins/grin.gif

Neg2LED: Let me know if you're ever coming to this side of the continent. Would be good to meet a few other Aussie flashaholics. Since you're in Melbourne, you ought to look up HotBeam. That guy is just amazing.

ok.... my real name is Andrew, but then i told you all that. i might as well tell you now that im only 12 /ubbthreads/images/graemlins/wink.gif. i know tons of stuff thoguh, so dont let this put you off /ubbthreads/images/graemlins/smile.gif. bye!

[ QUOTE ]
Neg2LED said:
i might as well tell you now that im only 12 /ubbthreads/images/graemlins/wink.gif. i know tons of stuff thoguh, so dont let this put you off /ubbthreads/images/graemlins/smile.gif. bye!

[/ QUOTE ]

Howdy Andrew,

FWIW, I suspected you might be on the young side but I don't see how that matters a wit. Do you?

Neat thing about this here Internet, stuff like that doesn't matter, right?

Welcome to the fray, looking forward to more with you.

Doug Owen

meh, i thought you might guess /ubbthreads/images/graemlins/wink.gif. yeah, i guess you are right, on the internet it doesnt matter how old you are, just as long as you can do what you are asking for. well, im considering running off the first batch of these Joule Theives, i just want to know: would you prefer a varsion that can take AAs, AAs+AAAs or AAAs? thats the real thing i want to know, cos if you want AAs and possibly other kinds, then the case will be longer and have a battery door, but if you are happy with AAAs then it can be smaller and you open up the case to change the batt.

does anyone know of places that will:
Make me a whole lot of little PCBs cheap
Sell me 100m of 38SWG Enameled Wire cheap
'' '' 100 Ferrite Beads cheap
'' '' 100 BC549 Transistors cheap
'' '' 50 AA and 50 AAA battery holders
'' '' 50 cases that will hold AAs
'' '' 50 that will hold AAAs
and sell me 120 1kohm 1/8w resistors
ALL CHEAPLY! i dont care if i have to got to different places to get it all, i just want all that stuff for CHEAP! (im gonna make 50 white, 25 blue, 5 for me and 20 for BYO led...)

thanking you and killing horsies /ubbthreads/images/graemlins/dedhorse.gif,
Andrew.

P.S. im not REALLY killing horsies!!!

Being a Yank, all my sources are US. We tend to 2N transistors here, I'm not even sure I can find specs on BC629s.....

I've got a pile of various sizes of 'magnet wire', if you can tell me what it is in AWG or decimal inches I should be able to give you some (assuming we can sort out shipping/customs).

I'm not sure you really need a PCB for such a simple circuit, if you go that way, you might consider battery clips soldered into the board.

There's a lot of different types of ferrite in the world, you'll need to get some samples to see what will work. I've bought a dozen or so types, some work far better than others. For sure this is 'the key to the castle'.

In a former life I worked for a company that made 1500 dual flourescent lights a day, by hand. It was a very similar one transistor oscillator with a 3 winding transformer (need to step up to very high voltage from the 12 volts).

I think you're off on a grand adventure, you're about to learn a whole lot about what it takes to make commercial products, good on ya as they say.

Doug Owen

Hey Doug,

How more / less efficient is the good ol' joule thief compared to the "Linverter"? What are the pro's / con's of these two. It seems that the linverter is easier to put together.

http://www.candlepowerforums.com/ubbthreads/showflat.php?Cat=&Board=UBB14&Number=486193

It's super interesting that these circuits are so less efficient, but they seem to always draw a lot of attention! Personally, I know I love the thought of seeing all this bright light pouring from this little dead AA battery I was about to toss! What a feeling! (It's the frugalness in me)

BTW: Would it do any good to have a linverter / joule theif combined with a circuit like the one you designed for the milky candle? This way you could have full control over the ma to the LED with different degrees of light..??