Electronics > Beginners

Boat Motor Trim Sender Design Question

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metrologist:
Can you imagine how they did the gauge? It's broke too. I suspect there are two magnetized discs and they have pulled off of their white bushings. The coils produce the magnetic field to rotate the discs, shaft, and needle accordingly...

The orange plastic was crumbling so I had to glue many pieces together...

floobydust:
I would suspect they are using off the shelf automotive fuel gauge parts, at least for the gauge. Look closely for any lettering or markings on its plastics etc.
The tank senders are common resistances. American common value is 240Ω-33Ω, GM 90Ω-0, Ford 158Ω-16Ω closest to what you read, and some European one is 190Ω-0.
I'm not sure why the sender is a rheostat, you normally don't have that much power going through it assuming a 12V system.

Kim Christensen:

--- Quote from: floobydust on June 10, 2023, 09:08:46 pm ---I'm not sure why the sender is a rheostat, you normally don't have that much power going through it assuming a 12V system.
--- End quote ---

Wire wound was more reliable than carbon and other technologies of the time. This is especially true in mechanical sensors where the wiper will sit and "jiggle" in one spot for long periods of time.
This changed when they started making POTs out of conductive plastic which is even more durable than wire wound.

Circlotron:

--- Quote from: floobydust on June 10, 2023, 09:08:46 pm ---I would suspect they are using off the shelf automotive fuel gauge parts,

--- End quote ---
That would account for the nonlinearity. Fill the tank up and the first quarter of fuel takes forever to consume so you think hey, this car is great! Then you forget about it until the last quarter goes yoink!

CaptDon:
Typically the most interesting areas of trim are from parallel to the bottom of the boat to an area of maybe +/- 15 degrees from parallel. Once trimming in a direction more positive than 15 degrees the prop is coming out of the water. Good resolution on the meter scale in the trim range would be a good thing. From +15 on up to about +60 you don't need much resolution because you don't run the tilt in that position while underway.
Non-linear in this case would make sense.

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