Two years ago we purchased a wireless collar system to keep our dogs safely on our property and off the road. The system consists of a base station and up to two collars. The base station pings the collars via an RF connection at around 2.5Ghz, and distance is measured via time of flight of the RF. If the dog is beyond the programmed range, a beep, and eventually a corrective shock, is given to the dog. Once the dog starts to return the shock stops, so no correction is given for returning home, which is a good feature.
The idea was great, however, implementation is poor. Just after the warranty expired, we started to lose collars. Replacements are $150 each. With the second collar dead, it was time to investigate. Beyond the collars not being sealed from the weather and getting wet, there was something else going on.
Having some background in RF, surface mount electronics, and switching power, I decided to see if the collars could be repaired. After dissection of the collar it became apparent some poor decisions were made.
The hot of the corrective shock is generated on the circuit board and passes to the dog through a wire and electrode. The shock returns to the ground of the circuit board through another electrode. That ground return electrode has a screw in it, which passes through the circuit board. That single screw is the only mount to hold the circuit board down. It is only accessible under the RF shielding for the 2.5Ghz radio circuit. Within 12mills (.012-inches) of the screw head are a bunch of passive components all attached directly to the RF IC chip. No thread-locking compound is applied to this screw.
The scenario became clear in my mind. As the dog runs around, the circuit board loosens the screw over time. When this happens the ground return is intermittent and the screw head touches the components coming directly from the RF IC. Basically, all of the high voltage goes through the sensitive RF transceiver, destroying it. Just a plain old horrible design.
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