Proximity detector circuit diagram

NE567 tone decoder/PLL IC

NE567 is a tone decoder IC from Philips. This IC has a built-in PLL circuit for AM lock detection and output drive circuits. The main function of the NE567 is to drive a load (usually an LED) when the frequency in its detection band is at the input of the IC. Center frequency, band input, output delay, etc. can be programmed using external components. Features of the NE567 IC include a frequency range of 0.01Hz to 500kHz, highly stable center frequency, programmable bandwidth, high noise rejection, capable of sinking 100mA of output, externally adjustable VCO frequency, etc. Common applications of the NE567 are highly Immunity to false triggering, dual audio decoding, remote control, ultrasonic control, monitoring frequency, etc.

NE567 proximity detector circuit

Proximity detector circuit

A simple proximity detector circuit using the NE567 is shown here. Pin 8 is the output terminal inside the internal output driver circuit IC . This pin goes low when the input frequency of the IC (PIN3) is in the detection band. Resistor R7 and capacitor C4 set the oscillation frequency. These oscillations are picked at pin 5 and it is coupled to the terminal assembly using capacitor C3. Terminal B picks up the base oscillation of transistor Q1 via capacitor C1, and couple. Q1 and Q2 form a two-stage collector-base biased 2-stage amplifier. R1 and R4 are the base bias resistors, the collectors of Q1 and Q2. A couple of C2 outputs from stage one to stage two. The signal is picked up and thus amplified and applied to the IC's input pin (PIN3) through capacitor C7. The 5233 forms the output filter capacitor and capacitor C5 determines the frequency band width of the received signal. C9 is the power supply bypass capacitor. C2 and R2 provide a phase shift of the VCO signal and this phase shifted signal from the IC is detected by the IC. When some nearby assembly is established, the capacitance of its terminals changes between the pick objects. This capacitance changes as the frequency changes, the IC detects this change and displays an indication. Resistor R8 limits the output LED current.