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Sensors /
Detectors:
Human Touch / Touch Switch Circuits
Sensors /
Detectors -- Main Page
Last Updated on:
Friday, June 04, 2021 01:53 PM
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Circuits Designed by Dave Johnson, P.E. : |
- 1.5V
TOUCH ACTIVATED SWITCH
A single 1.5v silver oxide button cell powers this complete touch activated switch
circuit for 5 years. It features both a
normally open and a normally closed set of solid state switch thermals.
It also has an adjustable sensitivity, which can be set for a touch
capacitance change as small as 1 picofarad.
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- 3V CAPACITANCE PROXIMITY
SWITCH
This circuit was designed to provide a touch activated switch function without an
external power supply. It draws so
little power that a single 3v battery will operate the circuit for many years.
It is discussed in more detail in the section on
Capacitance Proximity Switch Technology.
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- 5V
CAPACITANCE TOUCH ACTIVATED MOMENTARY SWITCH
This circuit is discussed in more detail in the section on Capacitance Proximity
Switch Technology. The circuit is powered from a standard +5v supply. It has both a
source and sink output that change state whenever a metal button connected to the
circuit is touched. An earth ground reference is required.
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5
VOLT MOMENTARY OPERATION TOUCH SWITCH
This simple circuit uses a single IC to form
a nice touch switch circuit. A single
transistor forms the remote active switch sensor. Multiple switches can be wired in parallel.
The switch circuit can be located about 500 feet from the control circuit.
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- 12V
TOUCH SWITCH EXCITER CIRCUIT
This circuit is designed to generate a 20KHz pseudo sine wave signal that can power
about 50 remote touch activated switch circuits. It can support a cable length of about 2500 feet.
A typical remote switch circuit is also shown as well as a receiver circuit
for those switches.
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FINGER TOUCH ACTIVATED SWITCH
It does not get any easier if you want a solid state switch that is activated by
the touch of a finger. Two small metal pins route voltage through the finger skin to
a MOSFET switch. The circuit is great for situations where a membrane type
mechanical switch is not desired.
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Door Knob Alarm
Many companies offer
simple alarm devices for personal use in bedrooms or hotel
rooms. A metal chain attached to a box holding the electronics
is placed around the inside doorknob of a wood door. Anyone
grabbing the knob from the outside is detected.
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- HIGH
POWER TOUCH SWITCH EXCITER CIRCUIT
If you have hundreds of touch switches that need an excitation signal, then this
circuit is what you need. Its 20KHz 20v
peak to peak output signal can supply up to 3 watts of touch switch excitation
power.
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