Vendors Corner > Tim's Universal Timers

Mounting a motor speed sensor

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Tim Wescott:
Some versions of the TUT programs sense the engine or motor speed.  This is how you mount the bits.

The system uses a Hall sensor mounted on the plane, and a 3mm rare earth magnet mounted in the spinner.  The top picture shows the complete system mounted in a plane (with a partial spinner).

The next three pictures show the Hall effect pickup, glued to a piece of aluminum -- this was glued together with normal 15-minute epoxy glue about five years ago, and is holding up well through perhaps 100 flights.

The final picture is a spinner backplate, with the magnet mounted.  The hole was made with a 1/8" diameter end mill so that it doesn't go all the way through.  Then the magnet was glued in so that it is captured by the epoxy.  This has lasted about as long as the pickup.

Tim Wescott:
Here's a video showing how the spinner and pickup work together in the aircraft; this should give you an idea of how to mount the pickup in the aircraft.

katana:
Any noticeable increase in vibration as even that little magnet would unbalance the spinner? Could add another 180 deg. opposite to balance out and then divide the count by 2 for correct rpm?

Tim Wescott:
I was running the thing on a 46LA, and didn't notice anything.  If I had felt it was going to make a big difference I'd have balanced the spinner, probably by removing material on the same arm of the spinner, and outboard of the magnet.  (And obsessing all the while with thoughts of whether the magnetic forces were messing up my balancing method).

Ken Culbertson:
I have never seen one of these on an IC.  What does it hook up to, what does it do and how is it better than a simple Tach?

Ken

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