Sunday, 2 April 2017
Splitting the transducer
The Parmain top secret laboratories have been bombarding a transducer with protons trying to get it to split. The DARPA program funding was pulled when the janitor said, "Just add a wire pigtail to the transducer, it's simple." Drat, time to write another grant request to DARPA. Maybe this time we could design a talking GPS for a boat. It should be simple enough for the average boater to use. To guide you to your destination it could say "Colder" or "Warmer." If you lurch to a stop it will say "Freezing."
Of all of the electrical things that exist on a boat, your transducer is the most reliable. It's always immersed in a salty chemical soup, gets dragged through the water often at very high speeds, and yet it keeps on working year after year. When I get a call dealing with a "no depth reading" problem, the first thing I suspect is the depth finder itself. Second could be the transducer face is covered with marine life having a rave party, and or has gotten knocked up. Third is damaged wiring. Fourth, and only very rarely the transducer has failed. There is an exception here. If it is a Garmin system, it may be suffering from thermistor-itis.
Of all of the electrical things that exist on a boat, your transducer is the most reliable. It's always immersed in a salty chemical soup, gets dragged through the water often at very high speeds, and yet it keeps on working year after year. When I get a call dealing with a "no depth reading" problem, the first thing I suspect is the depth finder itself. Second could be the transducer face is covered with marine life having a rave party, and or has gotten knocked up. Third is damaged wiring. Fourth, and only very rarely the transducer has failed. There is an exception here. If it is a Garmin system, it may be suffering from thermistor-itis.
Today's project started out with what appeared to be a bad split transducer that was feeding a single Garmin GPS 188C that was being used at two stations.
When I arrived on the scene, the 188C knows where it is, but displays a "Sonar Disconnected" message. Now it's time for "Tales from the thermistor."
This a fancy word for a thermometer. As the water temperature changes, the resistance in the circuit changes, and correlates to a temperature. You'll find these devices everywhere. In your oven, engine water temperature senders, hot water heaters, and inside transducers to name a few.
But as reliable as this device is, for reasons that aren't clear to me, it's not quite as reliable as the transducer's piezoceramic element that does the sonar pinging, and listens to the returning echo.
Back in days of yore, sounder module builders had from zero, to varying simple schemes to tell if, and maybe what kind of transducer was plugged into the module. In 2007 Airmar started to include an orange XID (transducer ID) wire. This allowed the transducer to tell the sounder who, and what it is.
Out comes a utility knife and I carefully slit the plastic cover away from the transducer cable. This transducer was made by Garmin. Note the green and red wires, they are not Airmar colors. With a flourish I cut and connect the green and white wires on the connector side together. It gets plugged in and the sonar disconnect message has gone away. Hah, see what my knowledge has wrought! Oops, the box now believes the transducer is there, but the old transducer isn't pinging. A new transducer was installed when the vessel was recently hauled, and I plug it in. It works fine. Okay this works about 99% of the time, but not this time.
If you see different colors, ie brown and blue when you slit the cable, this means the transducer was made by Airmar, and you will do the same thing only the colors will be brown and white. Remember this is on the connector side.
Part two of the problem is the old transducer had been split, and the cable was feeding two locations. This connection couldn't be accessed. This was a house boat, and a lot of wiring can only be accessed from underneath when the vessel is on land. Don't ask, it's a house boat thing. My best guess is the connection point became corroded, and Mr. Electricity encountered a road block.
The pull is buried in fiberglass insulation in the boats attic. Outlets had to be pulled from the wall, and wads of fiberglass insulation up top were jerked out to do this. I used over sized hemostats to extract what I thought was the wire, at the sort of half way point, and someone else bellowed, "that's the one," when I pulled on it hard. This is repeated at the lower helm to find the buried wire.
We're on the downhill slide now. The transducer wire is cut, and spliced wire for wire to the two connector end pigtail cables. The new cable for the 441s is connected, and we have joy at both helms.
2. Devices that are sharing a transducer, can't be on at the same time. Turn one on, only if the other one is off.
3. Do a good a good job with the splice, and if it lives in a bad place heat shrink the connections. For small wires the photo shows a good way to do the splice.
4. Don't call tech support for help with this discussion. They will all say "don't cut cables, your warranty will be in jeopardy, and we are holding your first born hostage to stop you." Just kidding they will be nice, but they will not think it is a good idea, and I don't want to be yelled at by them.
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