Browse Prior Art Database

Touch Plate System

IP.com Disclosure Number: IPCOM000092934D
Original Publication Date: 1967-Mar-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 24K

Publishing Venue

IBM

Related People

Heidecker, RF: AUTHOR

Abstract

This silicon controlled switch circuit is turned on by a finger contracting insulated touch plate 1. Plate 2 is capacitively coupled to plate 1 and connected to cathode gate 3 of silicon controlled switch 4. Load 5 is connected between the anode and ground. Resistor 6 interconnects the power source and gate 3. Plate 1 can be omitted and the switch can be operated by touching the dielectric material adjacent to plate 2.

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Touch Plate System

This silicon controlled switch circuit is turned on by a finger contracting insulated touch plate 1. Plate 2 is capacitively coupled to plate 1 and connected to cathode gate 3 of silicon controlled switch 4. Load 5 is connected between the anode and ground. Resistor 6 interconnects the power source and gate 3. Plate 1 can be omitted and the switch can be operated by touching the dielectric material adjacent to plate 2.

Due to the increased capacity at plate 2 caused by the finger contact, gate 3 can no longer follow rapid changes in potential at the cathode. The application of waveform A results in gate 3 being more positive than the cathode because of the voltage drop across resistor 6 caused by the capacitor charging current. The cathode gate current is regenerated within switch 4 until the switch is latched in the conductive condition. In the case of waveform B, the longer width of the positive pulse allows the anode voltage to approach the cathode voltage. This prevents the switch from latching on. The result is a momentary pulse whenever plate 1 is touched.

While waveforms A and B have been applied to the circuit in parallel with the power source, the AC component can be applied elsewhere in the circuit, for example, in a series circuit between load 5 and ground.

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