Capacitive proximity sensor detection circuit

Posted on Mar 28, 2007

Capacitive proximity controller usually consists of a radio frequency oscillation circuit and a detection plate. Figure 6-56 is produced with discrete components capacitive pro

Capacitive proximity sensor detection circuit
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ximity sensing detection circuit. In the figure, the transistor VT1 to surrounding parts constituting a radio frequency oscillation circuit connected to the sensor electrode metal} VT1 of the collector electrode as a detector. In the absence of other conductors near the sensing electrode, the oscillator circuit composed of a normal oscillation VT1, VT1 this time send emitter voltage RF signal by VD1, VD2 after detecting a DC control signal which enables the switch VTZ wine guide, relay energized electrical pull, turn the power of the controlled circuit; when the conductive base near the sensing electrode sheet, for any conductor near the sensing electrode are induced bun capacitor electrode sheet and the land between the capacitor the increase will reduce the amount of positive feedback oscillator until the oscillator stops vibrating swing. If stops the oscillator, the output RF detector circuit is no longer linear flow control signal, then it will switch off VT. So that the relay is de-energized, and the relay switch S Disconnect the need to release after re-closed, the oscillation circuit in order to enter the next state, otherwise relay Electric has been disconnected. G is the sensitivity adjusting capacitor, adjust its size can be adjusted oscillator start-up, the threshold stop vibration, thereby to adjust the controller to control the object distance and size of the project. In Figure 6-56, the inductance of the inductor L1 can be used as 1-6mH any color code inductance, if the inductance greater than 4mH, it is necessary to appropriately increase the value of G, in order to enable a smooth start-up circuit,

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