"Joule Thief" Circuit in a Flashlight Bulb? Yes!!!
Intro: "Joule Thief" Circuit in a Flashlight Bulb? Yes!!!
Investigating a Paradox:
Recently, I saw an "energy saving" LED flashlight for sale and it only used one 1.5 volt battery. I purchased this light and took it apart expecting to find a battery, bulb, switch and some kind of circuit on a board that would boost 1.5 volts to the higher voltage needed by any LED, especially a bright white-blue LED. I expected something similar to circuits used in my Instructable, "Joule Thief" circuits, crude to modern OR my Instructable, "Joule Thief" - no IC and no Transformer. I looked everywhere but only found a bulb, switch and a battery. This didn't seemed possible at first but then I wondered, could the "Joule Thief" electronics be entirely located in the flashlight bulb? Well, this possibility ruled out the use of any clunky, bulky toroid type of "transformer" used in the more popular "Joule Thief" circuits. It was time to try and cut open this bulb.
Recently, I saw an "energy saving" LED flashlight for sale and it only used one 1.5 volt battery. I purchased this light and took it apart expecting to find a battery, bulb, switch and some kind of circuit on a board that would boost 1.5 volts to the higher voltage needed by any LED, especially a bright white-blue LED. I expected something similar to circuits used in my Instructable, "Joule Thief" circuits, crude to modern OR my Instructable, "Joule Thief" - no IC and no Transformer. I looked everywhere but only found a bulb, switch and a battery. This didn't seemed possible at first but then I wondered, could the "Joule Thief" electronics be entirely located in the flashlight bulb? Well, this possibility ruled out the use of any clunky, bulky toroid type of "transformer" used in the more popular "Joule Thief" circuits. It was time to try and cut open this bulb.
STEP 1:
Well, isn't this amazing! Here is some kind of "Joule Thief" circuit so small it fits in the shell of a standard flashlight bulb. Especially notice the tiny and simple inductor along with the lack of any "toroid." The bulb had 1.5 volts and 0.2 watts stamped on it's metal shell. The brightness rating is 9 Lumens while the number of expected hours of use is 52 hours (In the past, I've seen 8 or 9 hours of use listed for incandescent bulbs).
STEP 2:
And now the test. Did I wreck this LED circuit when I cut it out from it's casing? Here we have a direct hook up to a 1.5 volt battery. When the final connection was made, it lit up brightly. What a move forward this design is!!! The hardware isn't super friendly for Instructable People but it is not impossible either. I haven't "decoded" the circuit board yet as the layering looks tricky. And I just wasn't ready yet to risk destroying this cool light. Maybe I'll do this later or maybe someone else will do it...
11 Comments
brit 6 years ago
Not a Joule thief. The only real Joule Thief is the one Posted by Big Clive. If you are using Big Clives " Joule Thief " name you should at least give him the credit for it. The Big Clive website.Clive fitted the Joule Thief into the base of a small bulb. It,s is there for all to see on the Big Clive website. He tells you step by step how to do it. His was also a lot tidier then this copy of that work. Give credit where it's due.
mguima 7 years ago
How to build a simple JT in a flashlight lamp:
http://www.bigclive.com/joule.htm
If you want the JT to be small, you should not use a PCB.
Dave Kruschke 8 years ago
Two or more batteries wired in parallel (plus to plus, minus to minus) would make this last longer. I've never thought about making the circuit work more "efficiently" or using more than 1.5 volts to power this circuit. Let us know if you come up with something that works for you...
RonE14 8 years ago
Any ideas how to make this ZXSC380 circuit work efficiently with 2 batteries instead of 1? I would like to make it last even longer. And has anyone tested how long it lasts?
dragontirex 8 years ago
This is exactly what I've found in a Varta one D cell flashlight, I think that it puts out less than 10 lumens but still good enough. Well, it did until I connected the supply voltage backwards and fried that little IC in there, good thing I had a 40mA one cell led driver (PR4402), just soldered it in and worked like a charm... except at lower brightens. I do like were they are going with this kind of bulbs though. Thanks for sharing. Cheers :)
SugarCluster 9 years ago
The green resistor thing is called inductor, and it works just like toroid transformers (which are also called inductors).
So basically it's more compact, but it's still a joule thief.
(To drive EL panels in some watches, they use voltage booster which uses tiny inductor and high frequency circuit. Basically same, but the joule thief feeds signal back to secondary wiring)
pandyaketan 10 years ago
Dave Kruschke 10 years ago
Dave Kruschke 10 years ago
But,... I think that I've verified that AgedP's June 8th outline is correct. My schematic of what I think AgedP said and what I've found by poking around with a meter immediately follows...
Dave Kruschke 10 years ago
Nevertheless, I'm still trying to get over the surprise of seeing a "Joule Thief" circuit inside the small package of a flashlight bulb!
AgedP 10 years ago