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Last Updated: November 30, 2017 02:27 PM
Circuits Designed by Dave Johnson, P.E. :
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 . . . Circuit by Dave Johnson P.E.-February, 2002

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 . . . Circuit by David A. Johnson P.E.-March, 2002

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 . . . Circuit by David Johnson P.E.-July, 2000

5v 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.   . . . Hobby Circuit designed by Dave Johnson P.E.-March, 2002

Capacitance Proximity Switch
Draws very low power - Ideal for battery-powered applications
6 Models Available - Call 806-368-7747




Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:

3 parts provide tenfold increase in switcher current -  08/22/02 EDN Design Ideas:  industrial-control circuits often derive their power from widely varying sources that can exceed the 40V maximum rating of popular switching IC s.  This design idea presents a simple, flexible, and inexpensive buck switcher that converts an input voltage as high as 60V to 5V at several amps.  The circuit is unique in that it boosts current with almost no compromise in performance, size, or cost __ Circuit Design by Wayne Rewinkel, National Semiconductor, Sunnyvale, CA

3-Input Stereo Audio Switcher -  Need more analog audio inputs for your stereo amplifier or home-theatre set-up? This 3-input Stereo Audio Switcher will do the job.  it works with an infrared remote control or you can just press one of the front-panel buttons to select a program source.__ SiliconChip

3-phaseProgrammable Controller for ON/OFF Motor -  Automatic on/off controller for a 3-phase electric motor can be made with a programmable time switch.  in this case a maximum of eight time durations can be programmed.  The system has two__ Electronics Projects for You

3-State Switch Interface Uses One Microcontroller Pin -  02/21/08  EDN Design Ideas:  A single microcontroller i/O pin senses the state of a three-position switch __ Circuit Design by Kartik Joshi, Netaji Subhas Institute of Technology, New Delhi, India

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 . . . Circuit by Dave Johnson P.E.-February, 2002

4 Digit Keypad -  This is an enhanced 4 digit keypad which may be used with the Modular Alarm System __ Designed by Ron J.

4 Digit Keypad Switch -  This is a universal version of the Four-Digit Alarm Keypad.  I'vemodified the design of the output section - to free up the relay contacts.  This allows the circuit to operate as a general-purpose switch.  I used a SPCO/SPDT relay - but you can use a multi-pole relay if it suits your application.   __ Designed by Ron J.

4.5V to 14Vin, 3.3V AT 25A Vout Switches at 2MHz -  A 2MHz, 3.3 V/25A step-down converter.  The LTC3838/LTC3839 can operate at switching frequencies above the AM radio band (fSW > 1.8MHz).  The high switching frequency permits the use of inductors of very small footprint, so that the entire circuit can fit within a 0.9in2 area with both sides populated.  The peak efficiency is 95%, and full load efficiency well above 90% at 25A, even at a frequency of 2MHz.  __ Linear Technology/Analog Devices App Note, Mar 29th 2012

4-Bit µPs A/D Converter Decodes Keypads Input -  10/13/94 EDN Design Ideas:  Fig 1 shows a MitsubishI M50927-XXXSP/FP 4-bit microcontroller decoding a 4×4 keypad using only four digital i/O lines instead of eight.  Saving four of a 4-bit µC's precious i/O lines couild be significant.4-bit µC's ADC provid __ Circuit Design by Ryoden International  Shanghai Ltd, Shanghai, China

4-Digit Alarm Control Keypad -  Alarm Control Keypads:  This Keypad is suitable for the Modular Burglar Alarm.  However, it has other applications.  Pressing a single key will energize the relay.  Entering the Four-Digit code of your choice will de-energize it.  __ Designed by Ron J.

4-Digit Keypad Controlled Switch -  Universal Keypad-Controlled Switches:  This is a Universal version of the Four-Digit Alarm Control Keypad.  I have modified the design to free up the relay contacts.  This allows the circuit to operate as a general-purpose switch.  I'veused a SPCO/SPDT relay - but you can use a multi-pole relay if you wish.  __ Designed by Ron J.

5 Digit Alarm Keypad -  This is an enhanced 5 digit keypad which may be used with the Modular Alarm System.  This switch will suit the Modular Burglar Alarm circuit.  However, it also has other applications.  The Keypad must be the kind with a common terminal and a separate connection for each key.  On a 12-key pad, look for 13 terminals.  The matrix type with 7 terminals will NOT do.  Choose the five keys __ Designed by Andy Collison

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 . . . Circuit by David A. Johnson P.E.-March, 2002

555 timer converted into pulse-width Modulator -  15-Feb-07 EDN Design Ideas:  Added CMOS switch enhances a PWM oscillator __ Circuit Design by Jordan Dimitrov, Tradeport Electronics, Vaughan, ON, Canada

555 Timer MonoStable using Pushbutton -  The two circuits above illustrate using the 555 timer to close a relay for a predetermined amount of time by pressing a momentary N/O push button.  The circuit on the left can be used for long time periods where the push button can be pressed and released before the end of the timing period.  For shorter periods, a capacitor can be used to isolate the switch __ Designed by Bill Bowden

5-Digit Alarm Control Keypad -  Alarm Control Keypads:  This Keypad is suitable for the Modular Burglar Alarm.  However, it has other applications.  Entering the First Four Digits of your chosen Five-Digit code - will energize the relay.  Entering the Full Five-Digit code - will de-energize it. __ Designed by Ron J.

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 . . . Circuit by David Johnson P.E.-July, 2000

5v 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.   . . . Hobby Circuit designed by Dave Johnson P.E.-March, 2002

6v Solid State Switch Solar Charge Control -  This is a Solid State Switch upgrade to the 6A, 6V Relay Based Solar Charge Regulator.  Solid state switching provides longer life, smaller size and higher efficiency than a relay.  in addition, the clock frequency may be doubled in order to better track battery load /charging requirements.  The parts cost is essentially identical.  One drawback__ 

7 Segment Display & Keypad -  Since the output buffer ofP1 can sink 20mA (each output pin, but maximum iOL for all outputs was limited at 80mA) , thus we can use P1 to drive LED display directly.  As shown in the circuit, Two common-anode 7-segment LEDs are connected to P1 with 180 Ohms current limiting resistor.  Each segment of two LED __ Designed by Wichit Sirichote

70m Ohm Protected Load Management Switch -  DN117 Design Notes __ Linear Technology/Analog Devices

8 Switcher Powers High-Performance µPs -  04/13/95 EDN Design Ideas:  The circuit in Fig 1  delivers 8A for driving as many as two of today's high-performance, high-speed µPs.  You can also optimize the design for lower current by changing a few components.  Most systems use a low-current 12V bias supply and a poorly regulated high-current 5V to power the logic.  However,  __ Circuit Design by Chester Simpson, National Semiconductor, Santa Clara, CA

8 x 8 Audio Video Switch -  8 channel switch.   __ Designed by Peter Jakab

8-Digit Code Lock for Appliance Switching -  This code lock is useful for appliances requiring exclusive or authorised use by those who know the preset code.  if desired, the code can be changed. The circuit doesn’t require additional AND__ Electronics Projects for You

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