This is a metal detector circuit used IC CS209A . A 100uH coil is used to sense the presence of metal. The IC CS209A has a built in oscillator circuit and the coil L1 forms a part of its external LC circuit which determines the frequency of oscillation. The inductance of the coil change in the presence of metals and the resultant change in oscillation is demodulated to create an alarm. The LED gives a visual indication too. This circuit can sense metals up to a distance of few inches.
Note:
The switch S1 can be a slide type ON/OFF switch.
The POT R1 can be used to adjust the sensitivity of the circuit.
IC CS209A Description
The CS209A is a bipolar monolithic integrated circuit for use in metal detection (Pendeteksi Metal)/ proximity sensing applications. The IC (see block diagram) contains two on-chip current regulators, oscillator and low-level feedback circuitry, peak detection/demodulation circuit, a comparator and two complementary output stages.
The oscillator, along with an external LC network, provides controlled oscillations
where amplitude is highly dependent on the Q of the LC tank. During low Q conditions, a variable low-level feedback circuit provides drive to maintain oscillation. The peak demodulator senses the negative portion of the oscillator envelop and provides a demodulated waveform as input to the comparator. The comparator sets the states of the complementary outputs by comparing the input from the demodulator to an internal reference. External loads are required for the output pins. A transient suppression circuit is included to absorb negative transients
The oscillator, along with an external LC network, provides controlled oscillations
where amplitude is highly dependent on the Q of the LC tank. During low Q conditions, a variable low-level feedback circuit provides drive to maintain oscillation. The peak demodulator senses the negative portion of the oscillator envelop and provides a demodulated waveform as input to the comparator. The comparator sets the states of the complementary outputs by comparing the input from the demodulator to an internal reference. External loads are required for the output pins. A transient suppression circuit is included to absorb negative transients
Lay out IC CS209A and diagram blog IC CS209A
Absolute Maximum Ratings
Supply Voltage ................................................................................................24V
Power Dissipation (TA = 125¡C).............................................................200mW
Storage Temperature Range ....................................................Ð55¡C to +165¡C
Junction Temperature...............................................................Ð40¡C to +150¡C
Electrostatic Discharge (except TANK pin) ................................................2kV
Lead Temperature Soldering
Wave Solder(through hole styles only) ...........10 sec. max, 260¡C peak
Reflow (SMD styles only) ...........60 sec. max above 183¡C, 230¡C peak