This was just a quick first pass at a "tug signal" device. I didn't want to make anything that hurt the dog, so the goal was to use a tone that helps the user and the dog react to the tug immediately. You attach the leash to the metal loop and load sensors close a circuit that emits a tone when there is sufficient force on the loop.
very simple controls and piezoelectric transducers make it a robust device.
This is a version that attaches to a leash. there is a load sensor that detects and indicates if the leash is taut. a piezoelectric buzzer sounds and the user is alerted to act to stop the tugging.
The pins slide out so you can insert the leash. You can see the load sensor in the middle.
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Tug prevention for dog walking

The goal for this project was to create a more human tug prevention method than might otherwise be considered by the end-user. These 2 concepts discourage pulling on the leash by emitting a high pitched tone which is somewhat disagreeable to the dog and creates a signal for both dog and person to stop the pulling action by stopping the pace until the pulling stops. Typically, and often recommended is to stop until the pulling stops, or to stop, turn and walk the other way.

Charles Floyd
Product Development Consultant Oakland, CA