circuit schematic help...

[Robocop]

I have finally figured out how to make a common joule thief and have now found that adding a small 22nf capacitor will greatly increase the efficiency. I have read the instructions online however can find no photos other than the circuit diagram which confuses me. The instructions that I found with the diagram link below spoke of feedback windings, base windings, and all kinds of things I had no idea of.

If possible could someone look at this diagram and maybe provide a simple easy to read sketch of where everything is connected? The link was not working when I tried to copy it to add here so I am providing the entire article. If you look about halfway down this page there is a post from colin55 where he explains the improved design and provides a schematic. From reading his post and looking at the diagram I was not able to figure it out. If I am looking at it correct it seems as if his diagram shows 5 wires from the toroid where there are only 4 on the original. Thanks for looking and sorry if the answer is simple yet I tried several attempts and it did not light....

http://www.instructables.com/id/Make-a-Joule-Thief/



I was able to figure out the original circuit by using a very simple diagram like the one below. and would really like to find one like this with the capacitor version....
http://www.google.com/imgres?imgurl...SearchBox&rlz=1I7ACEW_enUS367US367&tbs=isch:1

 

[cimino]

There are only four wires from the toroid. One end from each coil is twisted together, and that goes to the positive terminal of the cell. The other two wires go to the resistor and transistor/LED junction respectively.

Just make sure you have the transistor and LED connected up correctly. The negative LED terminal will be the side where there's a flat bit on the plastic. Maybe replace the transistor and LED with new ones if you suspect you've connected them incorrectly in the past.

For colin55's modified circuit, instead of twisting the coil ends directly together, they are connected through the resistor.
So now, one end of the previously shorted coils goes through the capacitor to negative.
And the other end of the previously shorted coil still goes to cell positive as before.
Also, because the resistor has moved, the old coil connection to the resistor now connects straight to the base of the transistor.

This diagram might help.

 

[Mr Happy]

You will find it easier in the long run if you can learn how to read the circuit diagram. It's not that hard once you learn what the symbols mean

Here's a link that may help you: http://www.kpsec.freeuk.com/index.htm

The diagram in the second link you posted is really just the same as the schematic only drawn with bendy lines and pretty colors.

One special thing to note is the location of the dots shown on each end of the coil windings. These are polarity markings and the polarity is important in this circuit. When you wind the toroid coil with two wires side by side the dots show the equivalent "ends" of the windings -- in other words the dots indicate corresponding ends of each winding in the pair. As you can see from the circuit and instructions, it is opposite ends of each winding that need to be joined together and connected to the battery.

 

[Illum]

the toroid is a transformer...handwound
there are better alternatives but the transformer version is the easiest
I made mine using the schematic on http://www.joulethief.com/kit.php using discrete components...you'll need 7 components but its all thru-hole

the schematic they gave


The schematic I used, simply rearranging some parts so they fit well in perf boards. the inductor can be any epoxy conformal choke.


The LEDs only getting something like 8ma and its drawing about 20ma at 1.5V, not bad for a two transistor flyback
I use mine to run an XP-E neutral, works quite well as a nightlight, but make sure your cell is sitting in a container as you gradually empty them they tend to wet their sheets. It should cut off when the Vbatt = VBE of the 2N2222, or the voltage drop across the transistor, around 0.6-0.7V. For really ferocious draining, I'm considering serializing multiple dead cells.

 

[Robocop]

Thanks for the help yet I am still a little ignorant as to the workings of this circuit. Cimino when I made the standard joule thief in the first diagram I did twist two of the wires from the toroid together. This twisted wire went to positive of the power supply and it worked pretty well.

Now for the modified circuit from diagram #2 are you saying I have to un-twist the wires that went to positive and connect them seperately? If so this is what was confusing me as I thought they had to stay twisted as one single wire.

 

[cimino]

Exactly. They are now untwisted and the resistor goes between those wires.
For the coil that has the other end going to the transistor/LED junction, the previously shorted end still goes to cell positive as before.
For the other coil, the previously shorted end now connects to the capacitor, and the other capacitor lead connects to cell negative.
Where the resistor _used_ to be, those points just connect straight together.

I agree with what the others have said. It would really pay to learn how to read schematics since they provide an unambiguous description of the circuit and are much easier to understand than a textual description. Especially once they get a bit more complicated.

 

[Robocop]

I did look up the symbols long before posting this and actually thought I had it figured out. I never realized the wires were untwisted in the modified circuit and now it makes things look much more simple.

I was also wondering what those dots on the coil were and now that Mr.Happy has explained that this shows the ends of the same wire it is much easier to grasp the big picture. I am attempting this circuit again tonight and we shall see if it works....thanks for the help.

 

[Robocop]

Thanks to all the help I have finally got the modified version working with the capacitor. Strangely enough it is not nearly as bright as the standard version without a capacitor. I am using a 1/4 watt 1k resistor and a 22nf capacitor...I saw some other 1k resistors that have different watts such as 1/2 and am curious if the resistor I have is the correct choice.

Does it matter which way the capacitor is attached or is it neutral? Any ideas as to why the circuit with the capacitor is much less in output?

 

[Mr Happy]

Sometimes it is hard to convey information adequately with words alone. To help everyone reading this thread here is a picture illustrating how the dots on the circuit symbol for a transformer relate to the toroid windings for the joule thief:

 

[Mr Happy]

Does it matter which way the capacitor is attached or is it neutral? Any ideas as to why the circuit with the capacitor is much less in output?

The capacitor is non-polarized and can be connected either way round. Also the power rating of the resistors won't matter in this circuit. Even 1/8 watt will be fine.

This kind of circuit is very pernickety in its behaviour (or even persnickety in its behavior). Tiny details like the number of turns on the toroid, the stuff the toroid is made of and the particular type of transistor can affect how the circuit works. Without detailed analysis in an electronics laboratory it would be very hard to say why the circuit works better or worse in different cases. It is one of those circuits where experimentation pays dividends. Especially try adding or removing a few windings, trying a different toroid or trying a different transistor and see if you can hit the winning formula.