In a powered parts feeder, what device indicates that there are no more parts left to feed?

• A. Sensor
• B. Push button
• C. Vision system
• D. Proximity switch

Answer: (A)

Sensing the presence of parts to determine when the supply is exhausted is the key idea. A sensor placed to monitor the hopper outlet or feed path provides a simple, automatic indication of emptiness: when parts are no longer detected, the sensor outputs a signal that can stop the feeder or trigger an alert. This direct feedback from a sensor is reliable and fast, making it a straightforward way to know there are no more parts to feed.

A push button is manual, so it doesn’t automatically tell you when the parts are gone. A vision system could also detect emptiness by checking whether parts are present, but it adds complexity and cost compared to a basic sensor. A proximity switch detects the presence of nearby metal objects and isn’t inherently suited to reliably indicate an empty hopper, especially with nonmetallic parts or varying part sizes.