How to know when a USB Type C is disconnected?

Having problem figuring out how to know when a USB type c is disconnected from a phone. Need an alarm to go off when it is disconnected. Once a usb c is disconnected there’s no power in the connector to alarm the rest of the phone/circuit. If anyone has any ideas it would be a great help. Thank you.

Welcome to the forum.

Detecting the loss of input power in a battery powered device is most often accomplished with a simple voltage comparator circuit.

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yes Paul that could get them what they want I was thinking an a App, Battery Charging Monitor you could down load however I have not seen one that has an alarm.

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How would that work without sensing current.

When USB is connected the power input is at 5V when disconnected it is at 0V.

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Just thought of a possible complication, USB OTG (On The Go).

Many, maybe most, phones have USB OTG which allows them to switch between working as a USB device and host.

I know very little about USB OTG, it may be that some, or all, OTG phones have 5V on VBUS all the time whether connected to a power source or not. If that’s the case a simple voltage comparator circuit won’t work.

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Thank you. Just trying to figure out how it may work without using any current now.