Faraday Switches, Capacitance operated touch activated electronic switches

Faraday Switches are capacitance proximity switches. They are tiny one inch cube electronic modules that operate using a capacitance change technique. The capacitance change threshold is adjustable using a multi-turn pot that is an integral part of the module assembly. The module's switch output is a FET transistor that has a voltage rating of 50v and is capable of switching 100ma of current. Three models are available. The FS1V-1 model is powered by a single on-board 1.5v button battery. The battery will supply enough energy for about 3 years of operation. The FS1V-2 model requires an external DC power supply from 1.5 volts to 6 volts. The FS5V-1 model also requires an external DC power supply the can range from 5 volts to 15 volts.
CAPACITANCE PROXIMITY SWITCH MODULE 1.5v BATTERY POWERED
Description Switch Features Typical Switch Applications Three Models are available: Switch Module FS1V-1 Specifications Switch Module FS1V-2 Specifications Switch Module FS5V-1 Specifications Prices Switch Modules -- Under Development Typical Module Connections

DESCRIPTION
The FS1V-1 model is powered by a single on-board 1.5v button battery. The module uses an electronic circuit to detect when an electrically conductive object comes in direct or near contact with a conductor connected to the module. A human touching a metal button or approaching a metal sensing plate, connected to the module, 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. A multi-turn adjustment screw on the module is used to set the minimum capacitance needed to activate the switch. When carefully adjusted, the unit will switch with only a small capacitance change. The module's switch output operates as a normally open momentary action push button switch. The transistor switch output will remain activated as long as the sensor capacitance is higher than the level set by the module's adjustment screw. In the Model FS1V-1 the switch module's battery supply is "floating", the switch output can be used to either source or sink current. The switch is rated at 100mA, 50v. Faraday Switches use true capacitance sensing methods. Unlike some "AC hum" type touches, 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 operation, an earth ground reference does need to be established. Each module provides a terminal for an earth ground reference. A screw terminal is also included if an external battery connection is desired. The switch module is packaged in an epoxy sealed plastic box that can be attached to a panel by means of a supplied adhesive foam pad. Modules with mounting feet are available on special order. Standard barrier type screw terminals are provided to make all of the electrical connections. The 1.5v battery is secured in a plastic holder for easy replacement. The battery should power the unit for at least 3 years. TOP
Prices
Single Unit Price: $75.00 + shipping for any of the three modules Quantity Discounts: Call David Johnson at 303-252-9787


Switch Features
On-board or external battery powered 3 years operation from 1.5v battery 100% solid state circuitry True capacitance sensing, not "Hum" Adjustable capacitance sensitivity 1pF capacitance change detection Transistor switch output, 100ma, 50v TOP	Excess of 10 million operations Switch can source or sink current Screw type terminals for easy wiring Small 1" x 1" plastic case size Rugged epoxy filled plastic case Adhesive pad mounting (standard) Cases with mounting feet (optional)
Typical Switch Applications
Finger touch activated Hand, arm or foot proximity Hidden behind walls or floors Easily cleaned for hospitals Vandal proof for schools Outdoor weather proof Interactive museum displays TOP	Replacement for pushbuttons Automotive touch activated Jail light or intercom controls Liquid level monitors Animal detection, Robotics PLC interface sensors Material handling monitors

Switch Module FS1V-1 Specifications
Enclosure = 1.0"W x 1.0"L x 0.75"H Electrical connection = 5 screw barrier type terminal block Battery power = Eveready 357BP, Duracell MS76B or Radio Shack #76 1.5v silver oxide cell Typical battery current = 4uA @1.5v, 20uA @3v Minimum output switch pulse length = 50mS Minimum capacitance change duration for switch detection = 50mS. Minimum capacitance change need to activate switch = 1pF Maximum total capacitance at sensor input = 50pF Output switch = normally open, DC floating, can source or sink current. Maximum switch current = 100mA Maximum switch voltage = 50v. Operating temperature = -40C - +60C Switch life = excess of 10 million operations TOP
Switch Module FS1V-2 Specifications
Enclosure = 1.0"W x 1.0"L x 0.75"H Electrical connection = 5 screw barrier type terminal block External DC power required, 1.5v to 6v Typical supply current = 4uA@1.5v, 20uA@3v, 220uA@5v Minimum output switch pulse length = 50mS Minimum capacitance change duration for switch detection = 50mS. Minimum capacitance change need to activate switch = 1pF Maximum total capacitance at sensor input = 50pF Output switch = normally open, source and sink outputs Maximum switch current = 100mA Maximum sink switch voltage = 50v. Operating temperature = -40C - +60C Switch life = excess of 10 million operations TOP
Switch Module FS5V-1 Specifications
Enclosure = 1.0"W x 1.0"L x 0.75"H Electrical connection = 5 screw barrier type terminal block External DC power required, 5v to 15v Typical supply current = 13uA@5v, 160uA @9v, 800uA@15v Minimum output switch pulse length = 50mS Minimum capacitance change duration for switch detection = 50mS. Minimum capacitance change need to activate switch = 1pF Maximum total capacitance at sensor input = 50pF Output switch = normally open, source and sink outputs Maximum switch current = 100mA Maximum sink switch voltage = 50v. Operating temperature = -40C - +60C Switch life = excess of 10 million operations TOP

Faraday Switch Modules Under development --- Available Soon
Remote Touch Switch Sensor These tiny 3/8 inch square modules are designed to be wired to a metal touch button or to a metal touch plate. Powered by a special signal from an Exciter/Interface module, the sensors can be separated from the control module by several hundred feet. These sensors are ideal for applications where multiple and widely separated touch buttons need to be monitored. The sensors can also be connected in parallel, forming an "or" logic function. Such a technique allows multiple switches in several locations to activate a single control function.
Exciter/Interface Module This module is designed to be used with up to 24 touch sensors. It supplies the remote touch sensors with a special signal and processes the outputs from the touch sensors. It operates in a momentary switch operation. Each module has 24 inputs and 24 outputs. All the outputs are standard TTL logic levels which can source or sink current. The outputs can be programmed for a normally high or a normally low. A single programming pin selects the polarity. The exciter/interface module can be installed several hundred feet from the touch sensors it supports.
24 Button Touch Switch Control Module This modules is designed to be used with up to 24 touch buttons or touch plates. It is ideal when the touch buttons or plates can be clustered around and near the control module. The separation distance between the touch buttons and the modules should not exceed 6 feet. As in the Exciter/Interface module the Control module has 24 inputs and 24 outputs. All the outputs are TTL levels and can be programmed for a normally high or a normally low. A single programming pin selects the desired polarity.
Typical Module Connections Sinking Current Mode Computer Connection Sourcing Current Mode Computer Connection Relay Driver Circuit External Battery Connection
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Contact: David A. Johnson, P.E. Last Updated on: 21 March, 2002 12:19:05 AM