Can someone explain how a joule ringer and joule thief works?

[rushi95]

Hi,

I have failed to understand how a joule thief and a joule ringer works.

JOULE THIEF:
Basically there are 2 reasons for the transistor to turn off:
1. saturation of the transistor
2. Saturation of the core.
Do both work? Which is better? How do I know my joule thief is working on which of the above effects?

JOULE RINGER:
I completely fail to understand a joule ringer. The schematic is http://laserhacker.com/?p=59. I have not seen any explanation regarding a joule ringer. Can someone please help me to understand how the transistor is turning on and off and how is it oscillating.

[Belfior]

I'll take a poke at this

In lasersaber's schematic at first C -> E is not conducting and the current passes through the lamp (resistance) and coil to the BJT base. When enough current gets to the Base the C- > E path will open. This path has less resistance than though the lamp and the current return through this path to the battery negative. Currnto the base will stop and the C -> E will close. Rinse & repeat

All this creates an on&off pulse at the toroid so you get a voltage spike and inducted power through the coils. So next round you get more current coming towards the collector from the battery positive side. The switching is so fast you see the LED on all the time.

Oh and joule thief and ringer are the same in my book. Give or take a few resistors or diodes they are usually the same. You have a resistance at the base (lamp or an actual resistor) so the C -> E will become the preferred route for the current to go and that is how it switches

[rushi95]

Hi Belfior,

Thanks for your reply. I have still some doubts.

1. The bulb has to be resistive? Lets say we have 1.5V at the input. Can a 2V LED be used in this setup?

2. The battery will take the path of the bulb and then through the base emitter to the negative. Is the bulb lit during this time? The current through the secondary will support the current in the primary and that will in turn increase the current in the secondary. This will happen till enough base current flows to allow the transistor to conduct. Once the transistor conducts - the current starts reducing in the secondary and base and will eventually block the CE path of transistor. That will create a voltage spike in the primary coil. What happens next? What is the polarity of spike?

This is what I think - the current due to the spike will flow through the bulb and base again. Which will again increase the base current and whole process repeats. Is it correct?

According to this working:
1. Bulb is lit in both the phases of working?
2. Transistor is ON only for a very short duration. So, less heating compared to conventional JT where transistor is ON for almost the entire period.

Am I understanding all this correctly?

[sm0ky2]

Sorry, I have to state my objection here.
(at the risk of starting yet another heated JT discussion)


I agree with Belfor's statement that JT and JR are basically the same.
My understanding is that the ringer oscillations are in the audible spectrum,
where-as the JT generally operates at higher frequencies.
But both names are used interchangeably, and the device does not really have
a set specification.


However:  the "path of least resistance" concept cannot be the principal that
answers the question.
Simply because the transistor will switch without a load or LED in the circuit.
The LED/lamp/etc. is basically an indicator.


TK is probably the most able to give a better description


I have seen this device in too many variations, that any attempt to describe the
behavior, would cause argument. The most common form (found in "how to's")
is what most people discuss. But this is neither the simplest nor the most advanced.
So, in my opinion, it causes a lot of confusion for beginners. But I'll give it a try::


If you ask me, I will tell you that while the inductor is charging (prior to saturation)
there is a current to the base. This opens the c-e gate
(or closes it, npn/pnp)
Once saturated, there is no more base current and the gate closes (or opens)
That might not be the best way to put it.


So, for a better understanding, maybe we should wait for TK to chime in.

[rushi95]

Thanks sm0ky2,

You are right. I am just a beginner to joule thief circuits and its getting confusing to understand the right working of its variants like joule ringer.

Can you please help me know where joule thief circuits are used?

If I have low voltage input, I can use a boost converter to light up the LEDs. And even the joule thief does the same job of boosting the voltage. Which is more efficient and practical to use for lighting applications? Any thoughts?

I got interested in joule ringer circuits because I see LED bulbs can be lit easily with 1.5V AA batteries. I could see them being used in villages to lit homes of poor people for 3-4 hours on a single charge. They could be recharged either through solar panels or hand crank generators or bicycles (10-15 minutes of human power can recharge a single AA battery). Would they work as I have described? Or am I missing something?

And will wait for TK to help in understanding the working of a joule ringer.

Thanks,
Rushi