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**PeterM** · 05-31-2002, 01:08 PM

Re: Newbie - Output Power needed?

Hi Mike

Good to hear that there's others out there as crazy as me :-)
Last thing first:

If i recall correctly (which is NOT always the case ;-)

P = E * I
P = E^2 / R
P = I^2 * R

where P is power in watts, Volts is E, Current (amperes) is I and Resistance (ohms) is R.

Regarding power rating output from the piezo-driver I have seen ratings between 500V to 5Kv. I think Stures design has an output of 1Kv - but I'm not sure - there are some circuit plans somewhere in the archives of this forum. In "The art of electronics" on page 168 there is an 200watts amplifier used to drive a piezoelectric underwater transducer. You might want to take a look at that?
I don't know if "more is better" - but it looks that way regarding range.
Please beware that this is high-power and burnt flesh doesn't smell as good as your Saturday barbecue..

Would you share with us how you're going to build the transducer array?

Regards,
PeterM

**Michael P** · 05-31-2002, 10:39 PM

Re: Newbie - Output Power needed?

Hi Peter,

>Hi Mike

>P = E * I
>P = E^2 / R
>P = I^2 * R
>Regarding power rating output from the piezo-driver I have seen ratings between 500V to 5Kv. I think Stures design has an output of 1Kv - but I'm not sure - there are some circuit plans somewhere in the archives of this forum. In "The art of electronics" on page 168 there is an 200watts amplifier used to drive a piezoelectric underwater transducer. You might want to take a look at that?

I have seen power ratings of between 400 watts & 1500 watts. What I can't understand is this:
If such high power is needed then how do sidescan systems work which run off:

1. 12V Battery (Marine sonic 600kHz, mobile PC + towfish)
2. Power from plugin cards (SonarWiz)
3. Have low power usage (Geo Acoustics Transceiver SS941 "150 VDC, 100 mA average, 320 mA peak")

Surely these 3 devices would fail the transducer if that needed high power wouldn't they?

>Would you share with us how you're going to build the transducer array?

With difficulty, I think. I had in mind paying someone with transducer-building experience
to construct them. But I now have more questions about this power problem so I will revisit
the transducers later on. I imagine though that building them will not be too complex.
Just 8 elements end on end to 400mm length embedded in suitable resin but I haven't really
considered the mechanics of this which do pose some logistical problems (bubbles, linearity).
My focus at this time is the pulse generator. I do not want to use a transformer as I think it
will distort the signal waveform at different frequencies. When I solve that I will be happy to
share the design with the forum.

Mike.

**PeterM** · 06-01-2002, 06:28 AM

Re: Newbie - Output Power needed?

Mike,

I don't know if I understand you correctly, but I don't see the problem here. If watt = volt * amperage then a driver producing say 5Kv at 100mA would deliver a power of 500Watt? That could easy be obtained from a simple small battery - yes?

I have a supplier of piezo elements, practically in my own backyard (actually the same as Sture) so I'm going for the homebuilt transducer array.

I also thought of ways to eliminate the step-up transformer in the driver design - but this seems to be quite hard, especially when you're no electronics wiz which I'm not.. So I think I'll start with a fixed frequency of 250KHz using the transformer design just to get something working that could serve as a platform for further experimenting..

Have you been thinking of the receiving end of the circuit?

/Peter

**Michael** · 06-01-2002, 07:10 AM

Re: Newbie - Output Power needed?

Hi Peter,

>I don't know if I understand you correctly, but I don't see the problem here. If watt = volt * amperage then a driver producing say 5Kv at 100mA would deliver a power of 500Watt? That could easy be obtained from a simple small battery - yes?

Please pardon my ignorance.

>I have a supplier of piezo elements, practically in my own backyard (actually the same as Sture) so I'm going for the homebuilt transducer array.

Which company is it? I will eventually need xtal elements myself. Perhaps we could get a discount on a bulk deal, maybe.

>I also thought of ways to eliminate the step-up transformer in the driver design - but this seems to be quite hard, especially when you're no electronics wiz which I'm not.. So I think I'll start with a fixed frequency of 250KHz using the transformer design just to get something working that could serve as a platform for further experimenting..

I believe Apex microtechnology may have very high voltage opamps that may do this without transformers. I'll have to look into it some more..

>Have you been thinking of the receiving end of the circuit?

Yes. Firstly preamp/buffer Lt1028. Then AD600 as Time Gain Control amplifier. Both these devices have excellent noise factors. The timing will be handled by a microcontroller. Haven't quite decided which one yet.

regards,
Mike

**Michael** · 06-01-2002, 08:19 AM

Re: Newbie - Output Power needed?

Peter,

I forgot to note that the preamp & TGC amp are part of the transceiver circuit.
The signal is amplified throught those devices and then fed straight into a
Data Acquisition Card inside the PC where it is digitized and dumped into memory
via DMA. Basically, each scan line is presented to the program without any CPU intervention
so bottlenecks will (hopefully) not occur.
The DAQ card is/will be a cheap (but good) one from adac.com

Mike

PS. I probably will have separate transmit & receive transducers. I know this may seem expensive
but:
1. Cost per piezo element will decrease
2. Element material can be different to better suit transmit OR receive so less power
will be needed overall or greater range attained.
3. Circuit will be simpler
4. Lower noise factor is more likely

**PeterM** · 06-01-2002, 06:46 PM

Re: Newbie - Output Power needed?

Mike,

The supplier I'm talking about is Freeoperm-piezo. URL http://www.ferroperm-piezo.com
Good idea about getting a discount on a bigger order. Check the website and see if you can find what you need - I'll be quite happy to call them since I speak their native language :-). There are a lot of additional information on their site - quite good.

Thanks for the tip with Apex I didn’t know them. Really nice products but also rather costly!! By briefly gazing at some of the datasheets for some of the power op-amps it seems to me that you still have to deliver the very high supply voltage to the amps (400 - 1000Volts)- at least the ones I looked at!
But very nice application notes - lots of transducer-driver examples…

I'm also going to use the AD600 since it's a nice piece and readily available. You might also want to throw a fast DA converter into your design to be able to control the TVG feature of the AD600 - this would be a nice feature when you have to calibrate your setup.

Also what about a band pass filter? I'm playing with the thought of putting one in after the AD600.

In my current design I'm going to use a PIC microcontroller to control various parts of the circuit. I hope to be able to only use one 16F877 or one of the newer parts which a much faster.

/Peter

**Michael P** · 06-04-2002, 07:44 AM

Re: Newbie - Output Power needed?

Peter

>Mike,

>I'm also going to use the AD600 since it's a nice piece and readily available. You might also want to throw a fast DA converter into your design to be able to control the TVG feature of the AD600 - this would be a nice feature when you have to calibrate your setup.

Good idea. What sort of resolution do you think is ok? 8-bit?

>Also what about a band pass filter? I'm playing with the thought of putting one in after the AD600.

The amplifier itself can act as a filter. the documentation for the AD600 gives some examples and this is what I am going to do.

>In my current design I'm going to use a PIC microcontroller to control various parts of the circuit. I hope to be able to only use one 16F877 or one of the newer parts which a much faster.

>/Peter

Mike

**PeterM** · 06-05-2002, 09:26 AM

Re: Newbie - Output Power needed?

Hi Mike,

>Good idea. What sort of resolution do you think is ok? 8-bit?

It gives you 256 steps to turn up the TVG input on the ad600 - I guess this is enough.

>The amplifier itself can act as a filter. the documentation for the AD600 gives some examples and this is what I am going to do.

Oh, I didn't see that. thanks for pointing that out!

/Peter

**Dale Hardin** · 07-13-2003, 07:42 PM

Re: Newbie - Output Power needed?

How are (both of) you progressing? I am also at the pre-amp,TVG amplifier, filter circuit design stage. However, I am better at circuit layout and board construction than design and programming. Do you want to collaborate on a design? Dale

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