Linear Capacitive Proximity Sensor

The project presented here is an analog capacitive proximity sensor. The circuit is from Texas Instruments application note. Most conventional capacitive proximity sensors produce a “1” or “0” output, this circuit produces a DC output that is a function of the size and relative permittivity of an object passing between the sense capacitor plates. Different sized and density objects will produce a different output voltage. The oscillator input for this circuit is a 50Khz sine source. The low frequency and sine characteristics keep RFI problems at a minimum. This proximity detector may prove difficult to construct because of the small capacitances involved, parasitic capacitances in the sensor circuit, and noise pickup. The circuit requires an external 50Khz sinewave with 1V_pp Signal. The circuit operates with a dual 15V DC supply.

Features

• Power Supply +/-15V (Dual 15V DC)
• Header Connector for Sensor Inputs and Outputs
• On Board Power LED
• PCB Dimensions 60.17 x 16.19 mm

Connections

• CN1: Pin 1 = +V 15V DC, Pin 2 = Frequency Input 50Khz Sine Wave 1V Peak to Peak, Pin 3 GND, Pin 4 = GND, Pin 5 = Sensor, Pin 6 = -V 15V
• CN2: Pin 1 = +V 15V DC, Pin 2 = GND, Pin 3 = -V 15V, Pin 4 = GND, Pin 5 = Output
• D3 Power LED

Schematic

Parts List

Connections

Application Data

Gerber View

Photos

Video

OPA132 Datasheet

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