Joule Thief LED Flashlight (Free Light)

[jmjpowerjoule]

Today, I changed-out that used transistor with a brand new TIP-31.

Findings:

1.) With one "AAA" battery; the Base-to-Emitter voltage sits right at about 1.05 VDC with a 1K Ohm resistor on the base.

2.) Everything stayed cool/cold to the touch, with no issues of ever-heating.

3.) The TIP-31 transistor takes up more room in the battery compartment of the flashlight.  So I had to use electrical tape to prevent shorts.

4.) The light emitted was noticeably brighter.

-I'd recommend this upgrade.

Tks

[Pirate88179]

@jmjpowerjoule

Great information, thank you. I have some TIP 3055's lying about, I wonder how they would compare to the 2N3904's I have been using? I know they can handle a lot of power so I suppose they use more as well? If I had more time, I would try all of this stuff out.

Bill

[jmjpowerjoule]

@Pirate88179

I also compared the newly purchased TIP-31 with the TIP3055.

They are almost exactly the same, but I thought that the TIP-31 might have been just a smidgin brighter, not sure.

Another reason that I used the TIP-31 is because the TIP-3055 can handle more power, so I saved it for a bigger use.

"General Rule":

Any NPN transistor that uses the TIP-220 case style, or similar, will be stronger and produce more output than the smaller sized transistors; ie 2N3904, 2N3555, 945C, etc.

-Tks

[jmjpowerjoule]

(Cont'd)

To connect the emitter wire to the "On/Off" switch, you'll need to 'hack-it."

-First, I used the diode test mode with my digital multimeter to test for continuity. After knowing that bit of info, I began taking the switch apart. I then mounted the emitter wire from the transistor into the switch.

I had to use an extra long wire for that, so I could take the guts out without inadvertently disconnecting that wire from the switch.

Now the light works without draining the battery.

-Thanks

[Pirate88179]

@jmjpowerjoule

Excellent!! Thank you for your comments. This makes total sense.

Bill

[jmjpowerjoule]

@Pirate88179

The brightness of my newly modified flashlight is not quite as bright as it was with three batteries and without the joule thief circuit. I am however, using an ordinary transistor.

-I am thinking of making the circuit stronger by replacing that transistor with a higher-output transistor and maybe just using a power-transistor. I'm thinking that a TIP-220 or a Darlington might be what I'll use.

I cannot wait to see the results.

Thanks Again.~

[jmjpowerjoule]

I went ahead and did this modification to one of my LED flashlights about three days ago now. The following day, I discovered that the battery was significantly drained.

I then reviewed the joule thief schematic and what I did with the guts of my light.

DISCOVERY:

-The joule thief circuit was actuated from the moment I placed the single battery inside the battery slot. I needed to integrate the "On/Off" switch to my circuit. So I connected the wire from my transistor emitter to that switch.

[the1969info]

Hi there, i love seeing the work of others with the joule thief circuit. I may have an answer for your one inch thorroid problem, Look up chilliqueen2007, his video super joule thief - rlc resonant circuit. It does not use a thorroid it winds a wire a few turns, also has an extra transistor.

I am trying to duplicate it, but i'm not there yet. I hope it works for you.

[Pirate88179]

@the1969info

Yes, thank you, I am familiar with his work. He does some great stuff over there. I have made JT circuits with air cores but the frequency gets really high. I will look over his work again. Thanks for your comment.

Bill

[RightQuiteNot]

You might want to try a "ReNu-IT" type alkaline battery "reconditioner". I bought one for less than $40 and have had incredible luck recharging regular alkaline batteries. (A lot of comments on the Internet suggest NOT using the "copper top" brand though.) I've got a big bag of batteries like yours that I've gathered from friends and have been able to restore a full charge. Good vid.

[Pirate88179]

Thank you.

I have never heard of that device and will look it up.

Bill

[RightQuiteNot]

ReNu-IT "Pro" type to be exact.

[GUILDGOB]

Boosting and better conservation of energy through the transistor/resist?

[Pirate88179]

The real secret to the joule thief circuit is that yes, it does boost the volts, but at the expense of amps (Ohm's law) BUT, thanks to the pulses, it flashes the leds at about 20,000/sec or so and they appear to be on all the time to your eye, but they are actually off half the time too. Leds and florotubes can be lit using the right frequency with mostly volts and hardly any power. It is a really cool circuit. try some and see.

Thanks,

Bill

[YortonJunction1]

looking through you video's Bill, everything fascinating. It is nice to meet a fellow engineer who is not afraid to experiment. Keep 'em coming.

Regards from the UK, Howard (YJ) :-))

[Pirate88179]

Thank you.

Bill

[Pirate88179]

I have a problem. I just checked that last 2 lights that I modified over a week ago and...the bats. are totally dead. This is weird because, if it were a short, I find it odd that both would be down from an odd short. These are 2 different manufactured lights that I modified the same way so, now I have to go troubleshoot and see where the power was going when the switch was off. I am posting this in the interest of full disclosure. I will keep you posted.

Bill

[harpbloke]

great to see you back yar. you inspired me to get a dozen used dispossable cameras from a local shop, but there are three different circuits, so i must send yo a pic and see what you think.

also, one of the ferrite cylinders inside the computer monitor lead might fit into a torch ok.

thanks for posting this vid.

[Pirate88179]

Thank you very much. Let me know if I can be of any help. The only flash circuit I am familiar with is the Fuji AA circuits. Others in my research group have had great luck with Kodak, and Fuji AAA boards but, I have not modded any of those.

Thanks again,

Bill

[jeannacav]

Good job, Bill.

I have several of those flashlights that have stopped working on the original batteries, and I will bring them back this way.

Thanks for showing the guts of that mod.

jeanna

[Pirate88179]

Thank you Jeanna. If you use one of your more powerful JT circuits you can light one with more leds than this one for sure. This one here is just the basic design.

Thanks,

Bill

[powercat000]

Hi Bill

do you know how many lumens your LED flashlight is producing ?

and have you tried CREE LEDs ? gratefully cat

[Pirate88179]

Actually, I do not. I can say that it is equally as bright as it was in its original form if not brighter. (subjective, I know) No, I have no tried the Cree leds...are they the square ones? If that is the case, then I have 4 of them. If you are talking about the 1 watt leds, I have only heard about them. I have brighter leds I could have replaced the super brights with, (265,000 lcds) but I didn't want to get the amp draw up any higher than it was with the stock ones.

Thank you,

Bill

[ZED74]

I dont know why all torches and small devices arnt made like this ... Great job from a clever guy . Power to the people !!! 5/5

[Pirate88179]

ZED74:

Thank you very much. I don't know why they are not made like this either. I doubt it is the cost as some high end led torches are over $80 and in quantity, this mod would only cost pennies. Maybe they want to continue to sell batteries?

Thank you,

Bill

[marthale7]

You can get these at Harbor Freight 9 led 2 for $4. I recharge the ""dead"" batteries, but have not done the small AAA batteries, I love your mod. It seems to me you could run a Joule thief with your earth battery and charge up your AA batteries from the ground.. But so far I love these flash lights for how cheap, and how much light they put out, and how long they run. I measured that when I used the 4.5 V it pulled 100 ma. I wonder how long your AA battery will last ...

[Pirate88179]

marthale7:

Thanks for the tip on the Harbor Freight lights, I will check them out at my local store. I don't think I would need a JT circuit to charge batteries from the EB as it already puts out about 2 volts. Maybe to get the power I need to dump it into a big supercap and then into an AA battery. I will see how long this battery lasts and report back. Thanks,

Bill

[jonnydavro]

Fantastic mod Bill.What you have there is a great demonstration of what the joule thief is all about and probably the neatest torch in town.They all should be made like this.I want one:-) Regards jonny

[Pirate88179]

Thank you Jonny. I know you could build one of these in about 5 minutes. The trick is finding a torch that has a large enough body to house the 1" toroid, after that, everything else is easy.

Thank you for your comment.

Bill