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Description         Features         Applications         Specifications         Typical Connections

Also available with LED indicator light.  Ask for model QTFS3X-L


Model QTFS3X Description

QTFS3X.jpg (5658 bytes)

The module uses an electronic circuit to detect when an electrically conductive object comes in direct or near contact with the module's "cap" input.  A human, touching a metal button or approaching a metal sensing plate connected to the cap input, increases the capacitance between the module and a nearby earth ground.

When the capacitance exceeds a specific level, the module circuit activates a transistor switch. Every 30 seconds the module automatically calibrates itself for maximum sensitivity.  The typical capacitance sensitivity change is about 5 picofarads.  A three position jumper sets the installed capacitance for 100pF, 200pF or 300pF of total capacitance.

The module has a "momentary" output, which will remain activated as long as the sensor input capacitance is higher than the calibrated level. The module’s output can sink up to 1 amp of current and handle voltages up to 30v.
Faraday Switches use true capacitance sensing methods. Unlike some “AC hum-type” touch activated switch circuits, Faraday Switches do not require the area around the switch to be rich in line-powered devices, such as fluorescent lamps. However, to insure reliable operations, an earth ground reference does need to be established. Each module provides a terminal for an earth ground connection. The QTFS3X model is an externally DC powered. The QTFS3X-L is identical to the QTFS3X model, but contains an indicator light. During standby operations the light glows dimly and glows brightly when the switch is activated.
The switch module is packaged in an epoxy sealed plastic box that is available with or without mounting feet. Standard barrier type screw terminals are provided to make all of the electrical connections. Dimensions are 1.0" x 1.0" x 0.75"
Faraday Switch Features
  • QTFS3X is powered by an external supply ranging from 3v to 24v  

  • 100% solid-state circuitry 

  • True capacitance sensing, not “Hum”

  • High capacitance sensitivity

  • 5pF capacitance change detection

  • Transistor switch output, 1 amp, 30v

  • Excess of 10 million operations

  • Screw type terminals for easy wiring

  • Adhesive pad mounting (standard)

  • Cases with mounting feet (optional)

Also available with LED indicator light. 
Ask for model QTFS3X-L

Faraday Switch Typical Applications
  • Replacement for pushbuttons.

  • Finger touch activated.

  • Hand, arm or foot proximity

  • Hidden behind walls or floors

  • Vandal-proof and weatherproof

  • Interactive museum displays

  • Automotive touch activated.

  • Jail light or intercom controls

  • Liquid level monitors

  • Animal detection

  • Robotics PLC interface sensors

  • Material handling monitors

Faraday Switch Specifications

Enclosure = 1.0”W x 1.0”L x 0.75”H

Electrical Connections = 5 screw barrier type terminal block

Supply voltage range = 3v24v

Typical Supply Current = 30uA, 100uA for the QTFS3X-L model containing a LED indicator light

Minimum Momentary Output Switch Pulse Length = 100mS

Minimum Capacitance change duration for switch detection = 50mS

Minimum Capacitance change needed to activate switch = 5pF, self-calibration every 30 sec

Maximum Installed Capacitance  = 350pF

Output Switch = normally open, sink current

Maximum Switch Current = 1 amp

Maximum Switch Voltage (sinking output) – 30v

Operating Temperature = -40C+60C

Switch Life = excess of 10 million operations

Typical Faraday Switch Connections

QTFS3X Faraday Switch Connection with Sinking Logic Circuit

QTFS3X Faraday Switch Connection with Relay Driver Circuit

Faraday Capacitance Proximity Touch Switches Six (6) Models Available           Prices           Place an Order           Project Photos

David A. Johnson, P.E.

Consulting Electronics Engineer

6601 County Road 6410    Lubbock, TX  79416-9717

Phone:  806-778-8407  Central Time Zone

email: dave@discovercircuits.com                    
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Last Updated on: 22 November, 2021 02:42:39 PM

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