on board transducer with topside display

[87TurboIroc]

Hey everyone..

I've been laying low for a couple of weeks trying to buy a new topside vessel. It seems I needed a larger "support ship" than my 18 footer to launch and retrieve an ROV from. Suffice to say I've more than covered my space limitation problem with the new "support ship" :mrgreen:

So I'm likely going to sell the smaller boat by spring. That means the Lowrance side scan system needs to come off and I will replace it with a cheapo fishfinder. I'm going to buy that cheaper finder today and will have a couple of weeks to play around with it before I install it. I want to see how it reacts to scanning left to right and also to an up and down scan as per my video. Just need some good weather tomorrow so I can experiment with that.

Of course the replacement boat has some issues from sitting, and the gremlins could come out and take all of my money. If so, the ROV project will be delayed but sooner than later I'm going to start working on it.

[87TurboIroc]

So I picked up a Humminbird 150 (around $80) and did some experimenting in my pool. The transducer is 200 KHz so it provides relatively sharp detail. I'm very pleased with the results. The 'ducer was ziptied to a PVC pipe and aimed horizontally. I would rotate it slowly for 90 degrees, then quickly return to the starting point back to the left. The slower the sweep, the better the resolution. The quick return produces a spike in the display that makes it easy to discern the starting and ending point of each sweep. Once a mechanical sweeper is made, the motion would be very consistent and the center of the sweep would represent the area directly in front of the ROV.

I'll make a better video when I get a chance, but this is what I filmed from my first testing. Keep in mind there is a pool wall causing the returns beyond 14 feet. Also I got mixed up next the later part of the video and was thinking something closer to the transducer would be lower down, but in fact closer to the transducer is higher just like shallow water would look.

http://www.youtube.com/watch?v=97viO5oHmhI

[thegadgetguy]

Cool! Does the topside unit come with the transducer, or is the $80 just for the transducer?

[87TurboIroc]

Yep it is complete with the transducer for that price. This boat already had the same model on it but the previous owner somehow manage to completely tear off the transducer! Nothing left but the screws and the wire handing there. I noticed it is a single pair approx 22-24 gauge, with a foil shield and bare ground wire, so it seemed easy enough to extend and the wire is light weight. So I can do this testing and then install this unit in the old boat to make selling it easier. Not gonna try to cut and extend this wire but at least I'll know what to expect when I buy one for the ROV (much later!).

[SSN626B]

@87TurboIroc,
I just picked up a Humminbird LCR 8000 on eBay for $75. The seller said that he used it for only one summer and then put it back in the box.
I figure that since the LCR 8000 has been discontinued Humminbird might be willing to give me a copy of the schematic so I can figure out where to tap off the return depth data (values) before it is converted for use on the LCD display.
Regards,
TCIII/SSBN626B

[SSN626B]

Hi All,
It turns out that Humminbird will not provide schematics of even legacy fish finders. Therefore I am going to have to reverse engineer my Humminbird LCR8000 fish finder.

I am hoping that Humminbird builds their equipment using a modular approach which might mean that the transducer driver/receiver, the control circuitry, and display are separate components interconnected in some logical way.

I have verified that my used LCR8000 is functional, so the next step will be to open it up. I assume that the power and transducer connectors attached to the back of the case should have their nuts removed prior to trying to remove the case?

Any help will be greatly appreciated to help speed the disassembly and analysis of the LCR8000 electronics.

Regards,
TCIII/SSN626B

[rossrov]

Hi SSN626B. I searched for any modern fish-finder diagrams on the 'net and found nothing of any use, so reverse engineering it seems to be. Closest thing was this: viewtopic.php?f=16&t=634&start=20#p6598

After cutting open my old Eagle fish-finder I have had some luck getting at the required signals:
viewtopic.php?f=18&t=1285
After starting the thread I read it should have been posted under the "Electronics" section

Just as a precaution I removed the nuts from the connectors first. As it turned out the connectors were connected via wires, not soldered to the board. Your FF may be different, so try removing the nuts first.

Interested to see how you go - I think that electrically there will be easier FFs to hack than the one I'm using

Ross

[SSN626B]

@rossrov,
Thanks for the info and the advice. Much appreciated.

I plan to open the LCR8000 this weekend and see what is inside. I am an Electrical Engineer and I have quite an assortment of electronic test tools so I hope that reverse engineering the unit will not be too painful:-)

Regards,
TCIII/SSN626B

[SSN626B]

Hi rossrov,
I have opened the LCR8000 up and there appears to be one main pwb with 3 processors on it. A 20 pin connector connects the main pwb to a pwb that is attached to the back of the case and appears to contain the transmit/receive circuitry and +5vdc power regulator. A 40 pin cable connects the main pwb to the LCD display which is attached to the back of the front of the case. A 20 pin ribbon cable connects the main pwb to the keypad.

It looks like I will need a portable o'scope to determine what signals are being sent from the main pwb to the transmit/receive pwb. I presently have a computer based o'scope which cannot be taken out to my workshop so it looks like it is time to purchase a portable o'scope for shop work:-)

I hope that I can separate the transmit/receive pwb from the main pwb and use an Arduino to trigger and process the return pulses and send them over either a wireless or hardwired link depending on how I will be using the sonar.

Regards,
TCIII/SSN626B

[rossrov]

The board configuration sounds promising. In contrast, my Eagle Magna II has only one board which is quite large. I only want a small corner of it!! Not sure where the Time versus Gain control is generated yet - in the micro or with circuitry in the analog section (more distant returns are amplified more than close-in ones). Will be interesting to see where your carrier frequency is produced - in the micro or an oscillator on the back-board. The LCR8000 sounds like it might be a good unit as a basis for Sonar experiments and practical use.

Standalone scope always good, but for now, any chance of setting up a PVC tube tank near your computer ? I ran the transducer cable out through a window to the tube on the porch