RC Lost Model Tracker Update

I’ve been using the tracker in my FPV plane for a while now and it has been working as expected. A couple of times I’ve forgotten to replace the disarm jumper on landing which just means the unit starts transmitting on the drive home. Although it’s sealed inside a foam wing, the beep can be heard when it’s active and the jumper replaced to shut it off.

Plane Stuck in a Tree

A few weeks ago I did get my FPV plane stuck in a tree and had to wait until the next day to get it down. The tracker triggered as it should and we could hear the beacon signal from home about 2KM away. From the end of the driveway with the simple yagi antenna it was easy to pinpoint the direction of the plane.

Jumper Improvement

One development that arose out of this was an improvement to the arm/disarm jumper. Overnight while the plane was in the tree it rained. The tracker stopped transmitting. I did some investigating and found that due to the very low power design, the arm/disarm jumper could be activated by water. I have changed the tracker firmware so that the jumper is now a capacitance. The tracker will only disarm if the correct capacitance is connected to the jumper pins. It now ignores the original shorting jumper as well as water and resistance.

The main advantage of this improvement is that you don’t have to worry about waterproofing the jumper pins. The plane can crash into wet trees and grass or puddles and the tracker will continue to operate. A side effect of this improvement is that the power consumption is also reduced. Standby time on a standard 140mAh CR2032 is now well over 2 years. Theoretically 5 or 6 years, but I don’t plan to sit around for that long to prove it.

Cold Testing

I have also tested the unit at sub zero temperatures. The tracker spent 2 days in our freezer at -12 degC. It operated correctly. The signal was load and clear outside the freezer. The sides and door are sheet metal but I think the back of the freezer is plastic and foam.

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