3.4.8 Metal Detector (LC Sensor)
An inductive-capacitive sensor for demonstrating the Low Energy Sensor Interface (LESENSE) is located on the top left of the board.
The LESENSE peripheral uses the voltage digital-to-analog converter (VDAC) to set up an oscillating current through the inductor and
then uses the analog comparator (ACMP) to measure the oscillation decay time. The oscillation decay time will be affected by the pres-
ence of metal objects within a few millimeters of the inductor.
The LC sensor can be used for implementing a sensor that wakes up the ZGM230S from sleep when a metal object comes close to the
inductor, which again can be used as a utility meter pulse counter, door alarm switch, position indicator or other applications where one
wants to sense the presence of a metal object.
LESENSE_LC_EXCITE
LC Sensor
LESENSE_LC_SENSE
100 Ω
100 nF
330 pF
470 µH
1.5 kΩ
ZGM230S
PB0
PB4
Figure 3.12. LC Metal Sensor
For more information about the LC sensor usage and operation, refer to the application note, "
AN0029: Low Energy Sensor Interface --
", which is available in Simplicity Studio or in the document library on the Silicon Labs website.
UG532: ZGM230S Dev Kit User's Guide
Hardware
silabs.com
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