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Question on toroids and Joule Thief

Voltage Spike

New Member
First post here (be nice). . .
I have messed with simple stuff when it comes to DIY DC circuits and have even made some pcb's from scratch but still with very simple stuff. Now I am very interested in making an efficient Joule Thief circuit that simply lights an LED and runs with a so called dead AA battery. Then comes the toroid. I never really understood inductors for years and now I have to. They seem simple enough but they can be used in multiple ways like suppression to clean up noise and also to make a transformer. I want to make a transformer that uses a transistor, a resistor, an LED, and a toroid, along with the AA battery. There are many designs on the internet. That is where my toroid confusion comes from. I gather that a ferrite toroid is better than an iron toroid so that is easy enough. But all the instructables and youtube videos seems like there is a lot of "winging it" going on. So my questions:

1. Best toroid type to use? Many different options out there when it comes to colors and specs.
2. High or low permeability?
3. Wire size smaller or larger with more or less wraps? What range in uH values are best for efficiency?
4. Single layer wraps only or can I wrap over existing wires when making my toroid?

That ought to be me going. I have some 30 AWG wire wrap wire and also some 32 AWG enameled magnet wire plus some thicker if needed. And I already bought some small toroids based on my internet research where one guy said this was the best one he found and had specs to show the facts. I bought these:


Thanks in advance,
VS
 
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mbarazeen

Member
1. Best toroid type to use? Many different options out there when it comes to colors and specs.
2. High or low permeability?
3. Wire size smaller or larger with more or less wraps? What range in uH values are best for efficiency?
4. Single layer wraps only or can I wrap over existing wires when making my toroid?
It should be very simple and you can make it to work by trail and error.
Toroid transformer -- you can pull one from an old computer power supply and it should serve the purpose
wire size -- what you have should work / you can pull from Ethernet cable
wrap over another winding-- is fine
 

MacIntoshCZ

Active Member
1. Best toroid type to use? Many different options out there when it comes to colors and specs.
2. High or low permeability?
3. Wire size smaller or larger with more or less wraps? What range in uH values are best for efficiency?
4. Single layer wraps only or can I wrap over existing wires when making my toroid?
Those questions are questions of newbie. Firstly read a electrotechnic book, then you will able to design it.
When selecting cores you should think about saturation of it.
Since i am CZ i can not recommend any EN book.
And best answer for all yours questions is: It depends.
Bmax for desing is in most cases Bsat/2. You need to stay in region with stable inductance. (relative permeability)
B=u*H
L=U*t/i
L= u*N*N*S/l
 

MacIntoshCZ

Active Member
If he wasn't a newbie, he'd know how to do it, and he wouldn't be asking.

Voltage Spike:Try here as a starting point.

He need to read electrotechnic book first - to know whats going on. This web is nice, but he needs to go step by step, from the begining...
His questions are same as mine when i started. So i know that he doesnt know whats going on...

VS - Can i give you a tip? Dont waste yours time on youtube videos.
 
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Voltage Spike

New Member
Thanks guys for all the help. That will get me going. I actually know how to assemble one but was looking for tips on best efficiency. I will go read my electronic books. There is always that one guy...:arghh:
Cheers
 

MacIntoshCZ

Active Member
Probably not electronics books. You need electrotechnics and transformers/coils book.Electronics book will be handy when you decide to make control boards etc...
 

MacIntoshCZ

Active Member
Would this be a good book to read on the subject at hand?

From my point of view good book is book that actually helps you to rise. When i was trying to calculate and design coils / transformers i have tried several sources/ books. When i was not satisfied i skiped to another one... When i started i failed to often. I started just by observation. I chose random cores, random number of turns, i made my own control boards and it obviously did not work. So i gathered some equations from websites. It was actually working. Well it works but it suffered from loud high noise and overheating. Than i readed some book about theory of magnetic field and another about transformers. Now its way better. I dont have teacher. My teacher failure is.
Just dont give up. I can recommend you only czech books. But there maybe something i can recommend you. But its maybe too complicated. Check books from Arthur von Hippel.
 

Voltage Spike

New Member
Ok, thanks for the info and link to that book. I am definitely going to be winding some cores. And I have an old low MHz oscilloscope too along with other hand held meters. I may have to buy an inductor tester though. I don't give up easy. Just never messed around with toroids before.
Thanks
 

MacIntoshCZ

Active Member
Ok, thanks for the info and link to that book. I am definitely going to be winding some cores. And I have an old low MHz oscilloscope too along with other hand held meters. I may have to buy an inductor tester though. I don't give up easy. Just never messed around with toroids before.
Thanks
You can calculate inductance of coil using eq. L=U*dt/di. Here is schematic for control board. I have built this schematic and adjusted frequency fo be around 10Hz. On time - Ron*Ct, off time Roff*Ct.
 
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Voltage Spike

New Member
You can calculate inductance of coil using eq. L=U*dt/di. Here is schematic for control board. I have built this schematic and adjusted frequency fo be around 10Hz. On time - Ron*Ct, off time Roff*Ct.
Thanks for the equation for calculating the inductance. If I see the need I may have to whip up a Visual Basic program for calculating some of this stuff. You will have to explain the pic or schematic for the control board you linked. I clicked on the second link too but the web page is all in Czechoslovakia language. Maybe I can find a converter on Google and cut and paste.

Found one to translate:

Inductors and properties of nuclei I
How to measure inductance
Most published methods for measuring inductance are based on the use of a sinusoidal signal. In pulse sources, however, we encounter a PWM signal, which is a rectangular waveform. Therefore, it would be very appropriate to measure the inductance under conditions as similar as possible to the operating conditions. I tested a very interesting method that we can use both to measure inductance and to measure the properties of unknown cores originating from various scrap, all under conditions corresponding to operation in pulse sources.

Description

The presented method is based on measuring the change of the magnetizing current Im in time. It is based on a well-known relationship

Im = (Ub * t) / L [1]

after adjustment

L = (Ub * t) / Im [2]

It is clear from the graphical representation that after the supply voltage Ub is applied for time t, the magnetizing current Im begins to flow through the choke. While the voltage Ub and the time t are constant, the magnetizing current gradually increases with the length of the time pulse. Thus, in order to obtain the inductance L according to [2], we will measure the change in the magnetizing current Im flowing through the choke at time t. With this method, we will also later look for the usability parameters of the unknown core.

Connection

The picture shows an asymmetric PWM generator with a variable opening time from 2us to 90us.

The circuit consists of a half-bridge driver IR2151, where only the lower half is used. The time constant for the closed transistor is set to Ct + Roff, the opening time is defined by Ct + Ron + Pt. Pt is a multi-turn potentiometer with which we change the opening time of the transistor Q. The choke in the drain of the transistor Q is charged while the transistor is switched on. During the switch-off, it is discharged via the fast Doff diode. Both magnetizing and demagnetizing current pass through the sensing resistor 0.11R. Every 100mV on this resistor indicates 1A of magnetizing current. We connect an oscilloscope to the OSC terminals on the sensing resistor. Oscilloscope ground on - and probe on +.

Buildlist

Doff - UF4004
L - measured choke
Q - SUP70N06 Ron - 10R
Pt - 10k (multiturn)
Rof - 100k Ct - 10nF

I will describe the exact measurement procedure in the next part.
 

MacIntoshCZ

Active Member
Thanks for the equation for calculating the inductance. If I see the need I may have to whip up a Visual Basic program for calculating some of this stuff. You will have to explain the pic or schematic for the control board you linked. I clicked on the second link too but the web page is all in Czechoslovakia language. Maybe I can find a converter on Google and cut and paste.
Basicaly ir2151 is pwm controller. Its turning mosfet on and off. On time is adjusted by Ron*Ct, and off time by ROff*Ct. By adjusting on time you can get to point when relative permeability drop to 1 in other words core is fully saturated. In practice coil is usable in linear region- stable inductance- current is rising lineary...By adjusting off time. You can adjust numbers of cycles. In other words wasted energy... W - L*i*i/2*frequency
This is neccesary! You dont want to blow you coil...
You are measuring voltage on .11R and using ohms law calculating current in coil. Also you need to measure time...
 

MacIntoshCZ

Active Member
Btw there are more articles here. But its in czech and it could be sometimes hard for you to understand. I bet you can find better sources ;)
 

Voltage Spike

New Member
Basicaly ir2151 is pwm controller. Its turning mosfet on and off. On time is adjusted by Ron*Ct, and off time by ROff*Ct. By adjusting on time you can get to point when relative permeability drop to 1 in other words core is fully saturated. In practice coil is usable in linear region- stable inductance- current is rising lineary...By adjusting off time. You can adjust numbers of cycles. In other words wasted energy... W - L*i*i/2*frequency
This is neccesary! You dont want to blow you coil...
You are measuring voltage on .11R and using ohms law calculating current in coil. Also you need to measure time...
Ok, I see now. You are using pwm to control the transistor. The one I am going to make just uses a transistor 2N2222 NPN and a coil and resistor to light an LED. Your design is more advanced but I can learn from it for advanced projects. I am making a low input version that uses a AA battery. But all of the info you are sharing is very good. I just need to study the math and formulas part and become familiar with the different properties and their names. But I will work hard at it.
Thanks
 

MacIntoshCZ

Active Member
Ok, I see now. You are using pwm to control the transistor. The one I am going to make just uses a transistor 2N2222 NPN and a coil and resistor to light an LED. Your design is more advanced but I can learn from it for advanced projects. I am making a low input version that uses a AA battery. But all of the info you are sharing is very good. I just need to study the math and formulas part and become familiar with the different properties and their names. But I will work hard at it.
Thanks
Ok. Schematic i posted is onky for coil measuring. I think i used irf3205 or irfz44n as transistor.
 

Voltage Spike

New Member
Ok. Schematic i posted is onky for coil measuring. I think i used irf3205 or irfz44n as transistor.
Ok, thanks for that info. Your circuit looks like a high power version based on the components used. Is that your website? Just curious as it looks like an informative place to get info although harder to use based on language difference. Sometimes websites have a button at the top where you can change language. No big deal as I can use Google Translator. :cool: And yes, I understand this is for making a coil measuring device. Took a few minutes to sink in. :p
 
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MacIntoshCZ

Active Member
Ok, thanks for that info. Your circuit looks like a high power version based on the components used. Is that your website? Just curious as it looks like an informative place to get info although harder to use based on language difference. Sometimes websites have a button at the top where you can change language. No big deal as I can use Google Translator. :cool:
No, its not mine. I just remember that site becouse i used it when i started.
I can also recommend danyk.cz. That site belongs to DiodeGoneWild. He has channel on YouTube. But as i said before, YouTube is not best place for knowledge, well maybe for math it is.. ;)
 

Buk

Active Member
I chose random cores, random number of turns, i made my own control boards and it obviously did not work. So i gathered some equations from websites. It was actually working. Well it works but it suffered from loud high noise and overheating. Than i readed some book about theory of magnetic field and another about transformers. Now its way better. I dont have teacher. My teacher failure is.
Just dont give up.
Can you imagine someone asking how much flour to use to make a loaf, getting the answer. "Try a kilo; if that ain't right try halving or doubleing it".
 

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