NVQ Key Finder Locator

The NVQ Model NF08 is an inexpensive ($10) key tag locator that is iOS compatible and can be found using the "Find Me" app.  The ability to do world-wide communication with this device with no subscription charges intrigued me and I bought a few to tinker with them.  Since it is possible to activate the sounder from the iPhone app, I could have it actuate something remotely (send a single bit command).

Left: cover.  Middle: frame.  Right: Board inside lower cover.

Underside of above board. 
Red:Battery+, Black: Battery- and system return,
White: Piezo sounder contact.

I was able to power the unit from a bench top supply and it worked normally down to about 2.4V.  Below that, it would continue to draw current and not go to sleep if the sounder was activated.

Normal current is about 4mA peak for about 2msec every two seconds.  When the sounder is active, supply current goes to 7mA continuous.

Scope on White terminal with respect to Black during a
sound commanded on.  4kHz at 8V peak.

On the Find Me app, this device shows a battery status bar.  It occurred to me that I could use this for the device to send data back to me.  I could lower the supply voltage to it and that would be one way to send me one or two bits of data back.  My initial work with this was unsuccessful and it would only show me a full battery in the app even when down to 2.4V supply.  I will continue invesigating.

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