Proximity Detector CS209A/D
Metal Detector Circuit :
A single chip metal detecor with a range of a few inches.
This is useful for decting nails or screws in walls and floors, or for locating buried mains cable.
◆ Block Diagram of CS209A
The heart of the circuit is a single IC the CS209A made by Cherry Semiconductor.
The detector, is a single 100uH choke.
The IC has an integral oscillatorm the choke forms part of an external LC circuit,
its inductance being altered by the proximity of metal objects.
It is the change in oscillation that is amplified and demodulated.
Led 1 will light and the buzzer will sound when the choke change sinductance.
Set up is easy,
VR1 is adjusted with the cjoke away from any metal source so that the LED lights and buzzer sounds.
The control is backed off so that the LED goes out and buzzer stops.
Now when the choke comes into contact with any metal object that alters its inductance,
LED 1 and the buzzer will activate.
Since I first wrote this article Maplin no longer sell the CS209A.
However the same part CS209AYN may be bought from ON semiconductors, direct link below.
Note that the package 626-05 is the 8 pin DIN type that is required.
CS209AYD8 Lifetime SOIC 8 751-07 1 Tubes 98 $1.68
Moisture Sensitivity level (MSL) for surface mount devices
(lead free measured at 260°C reflow, non lead free at 235°C reflow)
Separate Current Regulator for Oscillator
Negative Transient Suppression
Variable Low-Level Feedback
Improved Performance over Temperature
6mA Supply Current Consumption at VCC = 12V
Output Current Sink Capability
20mA at 4VCC
100mA at 24VCC
The CS209A is a bipolar monolithic integrated circuit for use in metal detection/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 at the tank circuit terminal.
◆ Data Sheet Proximity Detector CS209A/D - 83.0 KB Ver2
|Twin Loop metal detector|
|Lego Sound Sensor|