PZT Transformer HV circuit diagram complete

[Spencer DePue]

My final schematic is for a PZT driven high voltage source is completed. It is powered off of a total of 6 AA batteries. There are two 54 Khz oscillators that drive the SMMTF53P3S45 transformers. The power generated from the PZT's goes to a Voltage multiplier in full-wave operation. I have one question however.. With capacitor 2 in the 555 oscillator circuit rated at 10 nF, will this affect my 54 Khz square wave? I know that in an astable 555 timer circuit, that R1, R2, and C1 are part of the equation, but what about C2? Here is the schematic.

[Chris Trent]

First it looks like you need to do some more research on 555 timer circuits. Plenty of information is available elsewhere on the web so I'm not going to go into it. Besides, that's not really our focus here.

(You might want to look specifically at duty cycle and synchronization, and why are you using two?)

Second you may just want to get some parts together and test it, at least the driver portion. I guarantee you'll learn a lot just playing with it, and 555's are dead cheap and we're big on "Put your money where your mouth is."

You'll need an oscilloscope, but you should be able to scrounge one for less than $100 and you'll use it again I assure you.
You've probably already got a multimeter so no worries there.

Safety tip: Don't try for the multiplier until everything else is working PERFECTLY.
Reality tip: Make sure it suits your purpose. Most fusors use hundreds of watts.

[Tyler Christensen]

This is getting better than what you previously posted, but it's still pretty far from working properly. For one thing, 555's definitely should not be paralleled in this manner. Even if the frequencies are extremely close, a phase shift will develop between them and they'll just short between each other and your output waveform won't work anymore.

Also, 555's aren't rated for this kind of power output. You need to put a transistor such as a MOSFET between the 555 output and the input of the modules, this will step up the current handling that the 555's lack.

Also your multiplier is not wired properly, it is grounded and powered in the wrong input locations, double check how multipliers are hooked up.

[Spencer DePue]

I tested my 555 circuit with a multimeter. It works, but, I am confused whether it produces AC or DC. I used 4 AA in series to power the oscillator, which equates to around 6 volts. However, the multimeter reads 5.8 volts DC and 12.3 volts AC.. I don't know enough about the multimeter to know which one is correct.. It is really important for me to know if this is producing AC or DC. If this circuit produces DC output, how can I make the output AC without altering the 54 Khz signal?

[inflector]

Spencer,

What do the D and C in DC stand for?

What does the A and C in AC stand for?

How is AC different from DC?

What does the k and Hz in kHz stand for?

How do the A from AC and the Hz from kHz go together?

When you know the answers to these questions, you will know why you need an oscilloscope and why your question is puzzling at best.

[Spencer DePue]

AC= Alternating Current ( wave fluctuates between +/- on a graph)
DC= Direct Current (wave stays in one section of a graph)
Khz= Kilohertz (hertz is cycles in a wave per second)
Kilo= 1 thousand

Way to be both condescending and counter-productive Curtis...

[Admin warning: There is a low tolerance for flaming on this board, especially for new members. Keep it civil. -Carl]

[Rich Feldman]

Spencer DePue wrote:
> I tested my 555 circuit with a multimeter. It works, but, I am confused whether it produces AC or DC. I used 4 AA in series to power the oscillator, which equates to around 6 volts. However, the multimeter reads 5.8 volts DC and 12.3 volts AC.. I don't know enough about the multimeter to know which one is correct. ...

Spencer, you must learn enough about multimeters to understand those readings, which may appear to be contradictory . A good place to start is the user's manual. Behavior of AC ranges can be very different for different kinds of multimeter.
I suspect you used an analog meter. Try probing the battery pack with DC and AC ranges, then reverse the probes -- are the results much different than when you probed the 555 output?.
For the 555, try increasing C1 by 100x and probe output with headphones, or increase C1 by 10000x and probe with headphones or LED.

There are many forums well suited to questions and answers at this level -- basic high-school electronics, debugging a newbie's first 555, etc. At least one has been recommended to you.
I mean no disrespect in pointing out that www.fusor.net is not one of them.
Hot rod forums prefer that readers lurk until they know which direction to turn a wrench.
I bet you're smart and eager to learn. You'll feel empowered when you understand how analog and digital meter DC and AC ranges respond to mixed waveforms, and when you have mastered the 555. Enjoy the road!

[Chris Trent]

Curtis was attempting lead you to an answer that you probably already know; that if it has a frequency then it is by definition alternating in some form.

Your circuit also has a DC Bias one way or the other depending on what you are measuring it against so depending on your setup they could both be right.

Unfortunately a typical hobby multimeter is simply not up to the task of measuring accurately at any respectable frequency. Mine flakes out about 2KHz.

The tool of choice for measuring the frequency is an oscilloscope. It will also let you know that you have a nice clean waveform, and you can determine things like duty cycle etc. It is invaluable in power supply design.


I ran across this one the other day that might suit your purpose well:
http://www.seeedstudio.com/depot/dso-na ... p-681.html

I'm looking at modifying the code to make a bin counter out of it, but it looks like a decent entry level scope for the price.

[inflector]

Spencer,

I wasn't trying to be condescending. You are asking, as Rich pointed out, high-school learning-level questions. I responded at that level because that was appropriate for someone learning. Just giving you the answers won't help you learn. That's the same way people respond on physics forums to college students who ask questions.

As Rich pointed out, this is not the place to learn that level of electronics. This board expects a high level of self study. Others have hinted that you need to get out the books and this is the reason.

I was hoping you'd lookup the words on Wikipedia and then have a "Do'h" moment. I wasn't trying to be condescending.

You may not be in high-school, so that may seem condescending but I didn't intend it as such so I apologize for offending you. I'm 46 and there are plenty of high-school students (like Tyler [Edit: last year, he's at MIT now]) here that can run circles around my electronics knowledge despite the fact that I took E.E. at a very good school for two years.

But the question you asked displayed a very basic misunderstanding of the difference between AC and DC and how they might be measured. That's why an oscilloscope is a good idea, you can see the difference visually.

- Curtis

[Dan Tibbets]

Without resorting to preaching, I will attempt to answer you question concerning your multimeter confusion.-
A multimeter generally has settings to measure DC and AC voltage. The DC setting assumes a nearly constant voltage over some reasonable time frame. An AC or pulsating DC signal will confuse it and give some innacurate reading, probably well below the real voltage. The AC setting will average the AC voltage to give you a voltage reading that is generally the voltage RMS, which is generally the value used when you talk about AC voltage . The RMS (root mean square) voltage is generally ~ 66% of the pulsating peak voltage.
A general rule that I think is probably true, is that if you get a higher voltage on the AC setting than on the DC setting, the source is probably AC, or at least pulsating DC voltage.
To really know what is going on you indeed need an oscilloscope.

Dan Tibbets

[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