Bi-toroid Transformer of Thane C. Heins

[kEhYo77]

I think, that Auroratek core topology is basically a BiTT. It can easily be assembled using off the shelf C cores.

[Matthew Jones]

...and I can't even get my hands on toriods that big!

They aren't hard to build. Most of the toroids for power application are sheet metal. You can get coil of 12 inch at the hardware store for 10 buck. Some spray paint primer to isolate it. Build any size you want.

Then its weight based for capacity, 100 va = 2lbs.

You can also cast one with soft steel buckshot and epoxy. Same formula and they can go up to about 2 khz.

You'll have to read on winding them.

They don't cost a bunch, you can buy 1 kva versions for $150 but you'll have a hard time finding the right winding pattern and you can't reverse them. So if you buy for 120vac to 12 vac it will not work in reverse only step down. Even if it appears to work you'll be around 25 - 30% efficient. They have to be wound correctly for the application.

Matt

[sprocket]

One thing I do know is that the H-Bridge you posted is the way to go and the PDF of the DIY sine wave inverter is the best there is. The narrow duty cycle pulses of DC and then the increasing width as the sine wave reaches it's peak is a great expose.

I am not going to build every circuit that I need. With all of the microprocessor based stuff around all pre-made, I should be able to buy board sections and nail them together like carpenter builds a house.

Do you know if that 0-300khz board will connect up to an H-bridge? Does it have the 4 outputs?

I will look and be back.

Mike

@BroMikey - I think we may be thinking along different lines here. I'm thinking along the lines of verifying that there really is something special going on with a Bit-toroid transformer, whereas you seem to be gearing up to build power-applications from the get-go. For instance, the only reason I can see to use a H-bridge would be in serious power applications (eg. an inverter) whereas I'm thinking along the lines of being able to drive the bit-toroid primary with 5-10 watts, as in the videos you linked to. I keep coming back to the ferrites, there is no way you are going to be able to feed serious power into a primary of toroids the size that are used in the video - and I can't even get my hands on toriods that big!

So I'd be thinking along the lines of verification - if there really is something special about this setup, then I could always look to beef things up power-wise later on.

So precisely what kind of output are you looking for from of the variable AC power supply you're planning to build?

[Web000x]

Hey sprocket

You must be kidding because what I am stumbling onto is by accident and you are validating my finds but I am unsure of the best way to proceed.

Use an audio amplifier. Tune your primary to the impedance of the output of the audio amp, ohm's per feet of primary wire. Use a simple tone generator that you can find on a phone app or computer program. Run that into your audio amp. You'll more than likely not be really interested in the frequencies outside of the capabilities of an audio transformer with these size builds. You can use any audio amp in your house, just make sure your primary matches the output impedance of the amp.

Dave

[BroMikey]

Joking Right?

Haha, I don't think you need me for inspiration!


Edit: Oops, I see you have already pointed to a ICL3038-based sine-wave generator in a post! $18 seems a bit steep, but then, it is nicely built!

Hey sprocket

You must be kidding because what I am stumbling onto is by accident and you are validating my finds but I am unsure of the best way to proceed.

One thing I do know is that the H-Bridge you posted is the way to go and the PDF of the DIY sine wave inverter is the best there is. The narrow duty cycle pulses of DC and then the increasing width as the sine wave reaches it's peak is a great expose.

I am not going to build every circuit that I need. With all of the microprocessor based stuff around all pre-made, I should be able to buy board sections and nail them together like carpenter builds a house.

Do you know if that 0-300khz board will connect up to an H-bridge? Does it have the 4 outputs?

I will look and be back.

Mike

[sprocket]

@BroMikey - That 2KW inverter video is very interesting! I've been trawling through the comments looking for details. Wish he'd told us if it had a pure or modified sine-wave output though. He does say that it is >85 efficient, which would be up there with commercially available inverters and incredible for something that simple. The best DIY pure-sine inverter I had come across before this is available here - includes a very good article on the problems involved in designing one.

[sprocket]

Haha, I don't think you need me for inspiration!

The Ebay amp I was referring to is here. It seems to need a 28v AC supply and you'd obviously need to match its output to your primary. A quick search throws up the ICL8038 as a possible sine-wave generator - 0-300Khz output. Specs and example circuits are available here. I'm sure I have a MAXIM chip somewhere that I've used in the past for something similar, but is probably overkill for this. The circuit you posted is exactly what I had in mind, although maybe bipolar transistor drivers might be better for sines. I think finding suitable ferrites is the biggest obstacle though.

Edit: Oops, I see you have already pointed to a ICL3038-based sine-wave generator in a post! $18 seems a bit steep, but then, it is nicely built!

[BroMikey]

WHYME inverter

Homemade Power Inverter (Simplified). - YouTube


Published on Sep 6, 2013
Unit converts 12 Volts D/C to 115 Volt A/C square wave pulsed at 60hz. Unit output capable of delivering 2000 Watts of household power.

[BroMikey]

Simple Push Pull

Maybe like this? I think this is to simple.

https://www.youtube.com/watch?v=FB6Wz2wILpU

[BroMikey]

Sine Wave Generator

Here is one piece of the puzzle. This is a sine wave and square wave generator.

Then as you say Sprocket send this to a push pull circuit. This circuit can operate in many frequency ranges so is great for testing when trying to find the resonant values.

I just don't want to be limited to 10volts on the input.



New 10Hz 300kHz PWM Signal Generator Sine Square Triangle Wave Board | eBay

[BroMikey]

Vfd

Here is what I had my eye on but these generally only vary frequency between 0-500hz

These are variable Frequency Drives. Then I thought maybe some AC treadmill boards.

I want to input 120vac but at 0-5000hz.





Yaskawa GPD 315 V7 CIMR V7AM40P7 0 75KW VSD VFD Working | eBay

[BroMikey]

Amplifiers

Hi Sprocket

Here is a sinewave audio amp on ebay. Is this it? Also how many volts will the output muster up?

Rainbowkits Ebao 3 Wien Bridge Audio Sine Wave Oscillator Kit | eBay



Mike

[BroMikey]

100watt push pull

@BroMikey - I was also looking into making my own inductors but concluded it a bit messy, not to mention, hit-and-miss. Ideally, a system that would allow us to 3D-print them would rock, but until someone comes up with that, I'm afraid I'm stuck with getting lucky on Ebay.

Zero-crossing detection will not prove of much use if you are just interested in a variable-frequency AC supply. Also, that video you link to is altering its amplitude, not its frequency. A cheap & cheerful AC supply might be a battery-driven setup where a variable sine-wave oscillator drives a push-pull transistor pair whose load is the center-tapped primary of your bit-toroid. Or maybe your sine-wave oscillator could drive a commercially available audio amplifier whose load is again the primary. Just had a look on Ebay and there's a 100W one for $16. You'd need a separate power-supply for it of course - if it would work in the first place! Just thinking aloud.

Great work Sprocket

When you can show me the circuit on ebay. I am trying to get my head on straight on what is best. I am lacking in many areas of this work.

Here is something for .90 cents that could be used to power a flashlight?





Mike

[sprocket]

@BroMikey - I was also looking into making my own inductors but concluded it a bit messy, not to mention, hit-and-miss. Ideally, a system that would allow us to 3D-print them would rock, but until someone comes up with that, I'm afraid I'm stuck with getting lucky on Ebay.

Zero-crossing detection will not prove of much use if you are just interested in a variable-frequency AC supply. Also, that video you link to is altering its amplitude, not its frequency. A cheap & cheerful AC supply might be a battery-driven setup where a variable sine-wave oscillator drives a push-pull transistor pair whose load is the center-tapped primary of your bit-toroid. Or maybe your sine-wave oscillator could drive a commercially available audio amplifier whose load is again the primary. Just had a look on Ebay and there's a 100W one for $16. You'd need a separate power-supply for it of course - if it would work in the first place! Just thinking aloud.

[BroMikey]

Zero Crossing explained

Here I would like to take the time to explain what a ZERO CROSSING CIRCUIT is and why it is needed.




Zero cross circuit - Wikipedia, the free encyclopedia


"A zero cross circuit (or zero crossing circuit) is an electrical circuit that starts operation with the AC load voltage at close to zero-phase. This is in relation to solid state relays, such as triacs and silicon controlled rectifiers. The purpose of the circuit is to start the controlled triac conducting as soon as possible, so that the input and output voltages and waveforms are as close as possible. This is useful when the triac is used to control outlets, motors, ballasted lights, or other loads where voltage drops or waveform clipping could cause ill effects.

The point where the line voltage is 0 V is the Zero Cross Point. When a triac is connected in its simplest form, it can clip the beginning of the voltage curve, due to the minimum gate voltage of the triac. A zero cross circuit works to correct this problem, so that the triac functions as well as possible. This is typically done with thyristors in two of the three phases.

Many opto-triacs come with zero cross circuits built in. They are often used to control larger, power triacs. In this setup triac turn-on delays will compound, so quick turn on times are important."


There we see a quote from a source that defines terms. What Bi-toroids need is a higher frequency than the line (60HZ) to find the resonant point of reflection so energy can be most effectively bounded back and forth between the two secondary coils.

This may require a frequency of several thousand HZ. To do this a zero crossing circuit is similar to a pulsed dc circuit in that it can oscillate higher than the line yet also is designed to keep the peaks from being clipped off.

This is not a pulse DC circuit.

It should be part of an AC amplifier/oscillator. This is what a transformer primary wants and in the output AC is produced as well.







https://www.youtube.com/watch?v=XdCvJ1wZ0bA