PZT Transformer HV circuit diagram complete

[Dan Tibbets]

OK, I finally opened and looked at your schematic.
First- you can load images in JPG format directly to this forum. See the 'Attachments on the bottom of the input message box. That makes it easier for others. I copied you schematic below.

Looking at the schematic, the timers look like they are outputting pulsating DC. After passing through the transformer the voltage would presumably be boosted by some amount. But as mentioned, with two timers in parallel, the signals may be out of sync with each other- one would be putting out peak voltage while the other is a zero output. Summed together, you would have constant direct current, and the transformer would have nothing to work with. Apparently, the transformer passes this direct current ( are this type of pizoelectric transformers supposed to do this?). The diode bridges you have on the end of the circuit would convert any AC current (if present) to pulsating DC current- smoothed by the capacitors.
In short, the measured DC voltage is possibly accurate if measured after the diodes. 5.8 volts is reasonable if the batteries are not quite fully charged and/ or due to the expected voltage drop across any diode (~ 10% voltage drop). I don't know where your AC voltage reading is coming from (if real), other than some speculation that due to the imperfect function of the electronics, there is enough pulsating in the circuit to provide a small variable signal to the transformer. IE: The timer circuit signals may not be pure square wave pulsating DC, but have small rounded shoulders. This may be what is driving the transformers to apparently small voltage amplification.
Once again an oscilloscope used to probe various points in the circuit is needed to understand what is occurring.

[EDIT] Also, where is the negative output from the transformers going to?. I don't see any indication. If there is no output negative terminal in these transformers, can you reverse the input leads to get the necessary negative output voltage needed for a typical fusor? Or perhaps I'm misinformed. Is it Positive current indicated by your ( +) symbols coming out of the transformer, or shoud this be marked with a wavy line to indicate AC output. If it is only positive output, there is no need for the diodes. Transformers generally have two leads coming out , though one may be grounded to the core without a apparent lead exposed. Is that the case here?


Dan Tibbets

[JonathanH13]

Dan is spot on – the signals need to be synched together. In fact, you could drive these transformers nicely if the signals were locked 180 degrees out of phase with each other. There is a chip specifically for this kind of thing – I modified your circuit appropriately (see attached image). I also reversed the diodes in order to generate a negative voltage (and I'm presuming that the ‘negative’ output from the transformers is grounded).

[Dan Tibbets]

Err... 180 degrees out of phase? Wouldn't that give you a summed DC output. You need pulsating signals to drive the pizotransformers (I think) so wouldn't in phase signals be needed?

Dan Tibbets

[Tyler Christensen]

If it were parallel 555's as in the original schematic, yes out of phase would be bad. But the idea in this new schematic is to run the two inputs of the PZT transformer out of phase, it is simply a full-wave H-bridge in this design, it is more powerful than a single transistor.

[Rich Feldman]

Nice work, Jonathan.
But your circuit drives the two transformers with the same phase!
You get one inversion from the MOSFET inverter,
and another from reversing the + and - connections of PZT inputs.

[edit] Another view, following Tyler, is that you have an H-bridge driving two PZT's in series, with the center tap grounded. Why not disconnect the center tap, so each PZT sees half of balanced +-12V square wave? Then put the PZT's in parallel, so each sees all of balanced +-12V square wave?

The PZT schematic figure needs 4 terminals, + and - on input and output!
It's a 4 terminal device with no DC continuity between any pins.

[edit]
For anyone who wants to simulate this, the maker gives an equivalent circuit at
http://www.steminc.com/piezo/EquivCircuitPT.asp

Depending on the load, the PZT resonance width could be sharper than its mfg. variation. Then you'd need to use a matched pair of PZT's, or run them at independent frequencies and combine their power at the output of separate multiplier stacks.
I would suggest looking at standard app circuits for PZT drivers, that don't need to be hand-tuned for resonance.

[Spencer DePue]

Jonathan, thanks for the improved circuit diagram. I would like to use it for my senior project, but, I only have a couple months until the project is due and I don't think I have enough time to buy the parts. Is there any way I can use the 555 timer/ battery powered circuit and make it work with the Piezo transformers? A circuit diagram would be very helpful.

[Tyler Christensen]

You can do it with a 555 as long as you put some power transistor in, I would prefer a MOSFET in this particular application.

The attached schematic is probably the simplest way to make this work. It won't be nearly as powerful as the previously posted full wave design that is more complex, however this should work at least to some extent.

Note the 555 is shown without all its connections for simplicity, I'm sure you can easily find a schematic for that.

[Dustin]

The piezo behaves as a capacitor with inductance or a resonant circuit (in simple terms), and is open circuit to DC.
You need to drive this push-pull.

Piezos are a bit of an art to drive as the Q is high and the resonant frequency drifts a bit with temperature. They can be driven with a fixed freq but not very efficiently.
Some piezos have a feedback terminal to drive an oscillator at resonance.

It would be far easier to use laptop backlight inverters and make this a no brainer or buy a piezo with the driver than reinvent the wheel.

Steve.

[Richard Hull]

This discussion has ranged over a lot of effort and territory. A read of the FAQ

viewtopic.php?f=11&t=4516&hilit=FAQ#p27354

Will help teach about the power needed to do fusion.

Forget all attempts to get high voltage or high current in your supply until you read the above FAQ.

Regardless of voltage or current, until your finished product has the POWER capability, you will not be in the fusion biz.

Richard