I’m working on this one. In Fig.1, there is a schematic of a conventional Joule Thief. If the battery drops below 0.5V, the circuit will not start on its own because the battery voltage is less than the forward voltage of the base. In Fig.2, the Bat22 provides about 33 microamps through R21 and R22a
(Read More…)
The following is from a cached version of my late watsonseblog. 2011 Mar 15 Use Darlington for Joule Thief An email correspondent asked me if I have ever used a Darlington for a Joule thief. The short answer is no. The longer answer involves some lengthy explanations below. A Darlington pair connects two transistors so
(Read More…)
I have built quite a few germanium JTs, for the simple reason that they will start easily when the battery is below a half volt, and run the battery down to less than 0.2 volts while still putting out a small amount of light. Even after the conventional silicon transistor JT has run the battery
(Read More…)
Clarification: People have asked if the three windings explained in the schematic are in series or parallel. The three are in parallel, in other words, solder three of them together on each end. But make sure you use an ohmmeter to find and separate the other (4th or feedback) winding from the three. In Jan,
(Read More…)
In Jan 2009 I collaborated with Quantsuff and we tried different designs for a low voltage Joule Thief. The conventional silicon BJT Joule Thief (bipolar junction transistor) has a base to emitter forward voltage of about 0.55 to 0.6 volts, so if the supply is below this voltage it will not start. But once it
(Read More…)
I built this Blue Blinky and installed the partly used AA cell on Dec 1, 2007. For most of the next 21 months, on or about the first of the month I published a short blog on how it was doing. As the cell ran down it got dimmer and dimmer, but continued to flash,
(Read More…)
Ωne of the readers of my late, great watsonseblog sent me an email and asked some questions about the Joule Thief coil. But before I get up to speed I think it would be a good idea to read the warning at the end of this blog. my Q was: what is the relationship of
(Read More…)
This is a pictorial diagram of a Joule Thief (JT). It is meant to give a simple visual guide to those who wish to assemble their own JT. I’m also adding sort of a Joule Thief FAQ to explain in simple terms what a JT is. JT – WHAT IS IT? A conventional Joule Thief
(Read More…)
A few years ago, 2007, I believe, I blogged a few Joule Thief circuits on which I experimented. I used the 2N7000 low power MOSFET and the TN0702 (I’ll get to that one in a later blog). Choosing a MOSFET The 2N7000 is a small signal, low power MOSFET in the standard TO-92 plastic package
(Read More…)
I received a a lot of comments on my Supercharged Joule Thief circuit, which gives an efficiency of up to twice that of a conventional JT (more about this in my blog where I switch between JTs and measure the light output). The SJT requires a few additional components, nothing out of the ordinary. Essentially,
(Read More…)
