Hi Rossrov,
Unfortunately it will not be possible to setup a PVC tube close by to house the transducer and use the PC o'scope.
I have had a need for a standalone portable o'scope for a while so now is the time to get it and proceed with the reverse engineering effort.
The transducer board appears to use several 1 to 8 multiplexers that can adjust the gain by changing the feedback resistors in the front end high speed opamps. There does not appear to be any IF circuitry in the receiver. I believe that the ultrasonic frequency is 200KHz.
This is a very old design from the late 80s and probably reflects the design thinking of the times:-)
Regards,
TCIII/SSN626B
on board transducer with topside display
Re: on board transducer with topside display
Cool. That vintage would be my choice for this sort of work (reverse engineer, easier soldering and measuring...) Got that scope yet?? 
Re: on board transducer with topside display
Hi rossrov,
I will order the scope on Saturday after my cc rolls over on Friday It will be coming from the Northeast, so no telling when it will ship and get delivered here in sunny FL.
Regards,
TCIII/SSN626B
I will order the scope on Saturday after my cc rolls over on Friday
It will be coming from the Northeast, so no telling when it will ship and get delivered here in sunny FL. Regards,
TCIII/SSN626B
Re: on board transducer with topside display
Hi rossrov,
Sorry it took so long to get back to you, but I competed in the Sparkfun 2014 AVC in Boulder, CO this last June and a lot of my time was taken up preparing for the AVC.
I have decided that the used Humminbird will be too complex to try and use as a depth finder.
However I have found the Garmin Intelliducer http://g.factoryoutletstore.com/details ... y_id=30764 will do what I want in the way of depth finders.
It has an NMEA 0183 TTL serial output and provides just depth and water temperature.
An Arduino Uno can receive and decode the NMEA messages sent by the depth finder for display or telemetry transmission.
Sorry it took so long to get back to you, but I competed in the Sparkfun 2014 AVC in Boulder, CO this last June and a lot of my time was taken up preparing for the AVC.
I have decided that the used Humminbird will be too complex to try and use as a depth finder.
However I have found the Garmin Intelliducer http://g.factoryoutletstore.com/details ... y_id=30764 will do what I want in the way of depth finders.
It has an NMEA 0183 TTL serial output and provides just depth and water temperature.
An Arduino Uno can receive and decode the NMEA messages sent by the depth finder for display or telemetry transmission.
Re: on board transducer with topside display
Good to see you back again, SSN626B. The AVC looks VERY interesting and ALOT of fun! Re the Intelliducer, I looked at depth sounders as opposed to fish-finders with regard to modifying to get the transmit ping and raw echo signal out of them. There are probably several different techniques used by the manufacturers to get the echo signal strength, and some may use some sort of automatic gain control or software to separate unwanted echoes from say fish, and the bottom. There seems no analog input to the microcontroller in the Eagle Magna II Plus fish finder I am using, but the echo level is instead integrated so the micro is measuring the length of pulse. Short pulse = weak echo, long pulse = strong echo. I'm wondering whether or not the Intelliducer is potted. Here is another but with display, and cheaper apparently http://www.marinewholesales.com/en/product.php?id=2309 but may be potted and may have too much "smart" stuff in it that would complicate utilization. Have only been able to find one description of modern fish finder innards on the Internet, and no circuit diagrams to show if any given fish-finder or sounder would be suitable for use. The old simple type of sounder/fishfinder that used a spinning neon light or stylus and paper would be great.
Building from scratch doable for some electronics hobbyists, though the transformer needed to match the transmit circuit to the transducer would be a fiddle and would mean sourcing suitable transformer cores. Probably this is one reason why there is so little relevant subject matter on the 'net.
I'm considering another attempt on tracing the circuit of my FF (while it is still working
)If successful I'll then remove the transformer and any other bits I need to make up an output stage and "front end". Putting the complete fish-finder board as-is into a biggish enclosure is not practical because it forgets the user settings on power-down, and you need to be able to read the display in order to key in the settings reliably. Good thing about the Eagle Magna II Plus is that it looks like it has two transducer connections and transformers, one for down and another for side, so I may still have a usable unit after pulling the bits out.
Building from scratch doable for some electronics hobbyists, though the transformer needed to match the transmit circuit to the transducer would be a fiddle and would mean sourcing suitable transformer cores. Probably this is one reason why there is so little relevant subject matter on the 'net.
I'm considering another attempt on tracing the circuit of my FF (while it is still working
)If successful I'll then remove the transformer and any other bits I need to make up an output stage and "front end". Putting the complete fish-finder board as-is into a biggish enclosure is not practical because it forgets the user settings on power-down, and you need to be able to read the display in order to key in the settings reliably. Good thing about the Eagle Magna II Plus is that it looks like it has two transducer connections and transformers, one for down and another for side, so I may still have a usable unit after pulling the bits out.