User manual
68
Metal Detector
In order to measure the frequency, the micro control-
ler counts the pulses that the oscillator generates during a
given time period. This time period is called “gate time“. To
put it simple: the longer the gate time, the more precise is
the frequency measurement. The gate time corresponds to
the time between two audible clicks in operation. The turn-
ing knob allows you to adjust it stepwise to several values.
Aer switching on the device or turning the knob, the metal
detector executes its initialization routine. In rare cases it
may not switch to the measuring mode aerwards, but in-
stead continuously repeat the initialization routine (sound-
ing the tone sequence and lighting up the LEDs). You can
remedy this by turning the knob a little.
Fig. 3.2: Circuit diagram