Other Interest > DIY - Side Scan Sonar and towfish
Super long array
wreckreationaldivers:
Does anyone know what frequency Lowrance operate the down piezo in the LSS-2 and has anyone thought of using the piezo’s out of the LSS-2’s to make extra longer arrays? Looking at the X-ray I estimate the piezo lengths to be 200mm, and the quick test using an oscilloscope shows all 3 to have the same signature, if all 3 can be joined it would make the array of industrial length.
Also does any now what problems I might encounter trying this project?
Rickard:
Hi,
They use the same frequencies in all three channels, 455 and 800 kHz. This is actually a problem for them because since they also transmit and receive at the same time they have a tendency to interfere with each other. I use the LSS-2 with my Humminbird omitting the stupid downscan element with very good results. I wasn't sure the downscan element was the same as the others, but from your x-ray it looks as if it is. (I don't think they are single elements, probably at least two in each array). It would be a cost effective way to get elements if all three can be used, cheaper than sacrificing two Humminbird sideimaging transducers like I did when building my "very long array".
Problems may have to do with impedance mismatch since you must choose between wiring them in a serie or in parallell. None of those solutions will give the same properties as in a single element. The effect of such mismatch could be reduced efficiency, but it would probably not damage the unit. I have tested several wiring schemes with arrays with large circular elements and couldn't see anything but small differences in the images. Other problems have to do with mixed up pooling directions, damaged solderings, damaged silver coating and difficulties with lining up the elements while the resin cures. With some patience and precision I'm sure your project will be successful.
I must say I'm curious to see the result of this!
Rickard
wreckreationaldivers:
Thanks Rickard.
I am glad to hear that all three elements use the same frequencies; my original plan was to make a longer array by using the side elements out of two LSS-2’s, but if all three elements are the same I might as well use them and make one 3 time’s the length.
I hadn’t thought about connecting them in series, I was going to connect them in parallel as in the Humminbird which I stripped apart, Am aware of the differences between resistors and capacitor in either case, but what are the characteristic’s differences between series and parallel in piezo’s?
Looking at your very long array project I can wires connected to the elements but can make out if they are series or parallel how are they connected?
I am to use these on a fish with a long cable so ultimately I’m after strong returns and good images.
Jeff
Rickard:
Hi Jeff,
I made a quick sketch to show how the elements are wired. I'm not really an expert on electronics, but this is what people with insight into sonar design have told me. This wiring will result in the same over-all impedance as in a single element. I have made all connections outside the array body to be able to test other wirings if necessary.
I went out to test the 'naked' epoxi array after removing the aluminum profile and it worked well with some extra ambient noise. This is my most disburbing issue right now, noise. It could be 'ringing' or simply bad sound insulation in unwanted directions. Insulation can be improved, but I don't know how to reduce ringing. Connecting all elements in parallel?
Rickard
wreckreationaldivers:
Rickard
I’m not a sonar expert myself, but have a bit of electronic knowledge, whilst the overall impedance will be the same connecting 2 elements in series will double the amplitude thus it may be more than the head unit is designed to see.
Another quick thought is if connected in series is there a possibility of one piezo reverse powering the one it’s in series with?
As with the aluminium roughing and cleaning the surface before bonding should improve bond
Jeff
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