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Last Updated: January 01, 2018 04:02 AM
Circuits Designed by Dave Johnson, P.E. :

Secret_Panic_Switch -  Design an electronic switch which would be positioned behind a wall at several key positions and would be activated when an adult human hand was pressed against the wall at that position.  The best way to detect the human hand against a wall was with a capacitance switch.  The QTFS3X from Faraday switches looked like a perfect match.  The switch could be powered by a DC voltage down to 3v.  It required only 30ua of current.  It was quite small and would easily fit behind the wall. . . . Dave Johnson, Lubbock TX-DC Magazine - Issue 18 May 2011

Service Request Beeper -  A single press of a pushbutton switch turns on a beeper for one second but canít be activated again for 60 seconds.   . . . Hobby Circuit designed by Dave Johnson P.E.-September, 2005

Single Output 120VAC 200 Watt 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 David Johnson P.E.-February, 2010

Sink to Source Universal DC Converter -  As illustrated below, many control systems use an open collector transistor to turn something on.  Perhaps it is a LED light, a relay or a small motor.  However there are other systems which require a common ground connection instead of a common V+ supply connection . . . Circuit by Dave Johnson P.E.-March, 2011

Small Pushbutton Controls 10 Amps AC -  The circuit below uses a pair of long lasting lithium coil cell batteries to power a latching relay circuit.  With each activation of the small pushbutton, the relay is either latched closed or unlatched open.  Since coin cells canít provide the necessary peak current, a 500uF capacitor is used to store the needed energy.  The circuit standby current is kept very low by using a stack of five 100uF ceramic capacitors instead of the usual electrolytic cap . . . Circuit by David Johnson P.E.-January, 2012

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:

Safe Universal Mains Switching Box (Silicon Chip magazine, May 2006)  -  I (Bob Barker) didn't design this.  Bill De Rose (ex Dick Smith Electronics Kits Dept) came up with this brilliantly simple project which allows any low voltage switch or switching circuit to safely control any 240V mains-powered appliance up to 10A.  The uses are nearly endless.   __ Designed by Bill De Rose

Scanning 7-Segment & 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

 

Scheme improves on low-cost keyboard -  30-Oct-03 EDN Design Ideas:  You can easily improve on a previous Design ideas to produce a slightly simpler resistor arrangement with better timing balance between switches, using a single resistor value (Reference 1, Figure 1].  The use of a single resistor value, RS, in a series chain for the switch resistors gives the timing parameters a simpler format and should reduce bill-of-materials cost __ Circuit Design by Martin O'Hara, Telematica Systems Ltd, Cranfield, Bedfordshire, UK

Secret_Panic_Switch -  Design an electronic switch which would be positioned behind a wall at several key positions and would be activated when an adult human hand was pressed against the wall at that position.  The best way to detect the human hand against a wall was with a capacitance switch.  The QTFS3X from Faraday switches looked like a perfect match.  The switch could be powered by a DC voltage down to 3v.  It required only 30ua of current.  It was quite small and would easily fit behind the wall. . . . Dave Johnson, Lubbock TX-DC Magazine - Issue 18 May 2011

Security Keypad -  This Electronic Code Lock uses a 12-keys keypad is used to enter a password and open an electrick lock or any other device with a signal.  Uses an 8-pin PIC  12F629.   __ Designed by Jose Pino

Security Keypad II -  An improved version that can be used on security vaults, Doors with electric latches, Alarms, Safety devices and many other uses.  it uses an HiTACHI LCD (16x1 or 8x1) and a matrix keypad.  The HEX code is available for 16F84A and 16F628.   __ Designed by Jose Pino

Security System Switcher -  An audio signal can be used as a form of input to control any security system.  For example, an automatic security camera can be configured to respond to a knock on__ Electronics Projects for You 

Seismic Sensor -  My original "Deer Repellent/ Seismic Sensor" recommended using a speaker with a weight glued to the cone as a vibration sensor (see bottom of page) but it recently occurred to me that the speaker could supply the mass itself.  By gluing  __  Contact:  Charles Wenzel of Wenzel Associates, Inc.

Sense multiple pushbuttons using only two wires -  Sense multiple pushbuttons using only two wires figure 1Keyboards and numeric keypads often provide the user interface for electronic equipment, but many applications require only a few pushbuttons. For those applications, you can monitor multiple pushbuttons over a single pair of wires (Figure 1). __ Designed by Bernhard Linke, Maxim Integrated Products Inc, Dallas, TX

Sensitive Clap Switch Circuit -  This is the circuit of a very sensitive clap switch.  it switches ON/OFF a White LED or electrical appliances through claps.  The circuit can sense the sound of claps from a distance of 1-2 meters.  Condenser Mic picks up sound vibrations caused by the clap.  These sound vibrations are given to the inverting input (pin2) __ 

Sensitive Temperature Switch -  This temperature switch has a high sensitivity and is quite reliable.  Here, in place of a single transistor, a Darlington pair has been used for switching. At normal room temperature germinum diode__ Electronics Projects for You

Ser-Key 10-Key Serial Keypad Encoder -  Schematic only, no circuit description __ Designed by Reynold's Elec

Service Request Beeper -  A single press of a pushbutton switch turns on a beeper for one second but canít be activated again for 60 seconds.   . . . Hobby Circuit designed by Dave Johnson P.E.-September, 2005

Shock-Proof Remote Switch -  Using this circuit, you can control any AC/DC appliance remotely through inexpensive, low-voltage cabling and a standard push switch.  The circuit can easily support cable length up to 25 metres.__ Electronics Projects for You

Signal Detecting Auto Power on Unit -  The switch detector unit is shown in Figure 1, and uses an LM358 dual OpAmp, and a handful of other parts.  The relay switching device is a MOSFET, selected because of the almost infinite input resistance.  The 2N7000 shown is recommended because it has a threshold voltage of less than 3V and is fairly cheap, but virtually any MOSFET will work just as well, even if the gate threshold is a little higher.  An MTP3055 can also be used, as shown originally in this circuit.   __ Designed by Rod Elliott  ESP

Signal-Powered Switch Connects Devices -  05/10/12  EDN Design Ideas:  Use a switch to selectively connect a terminal, personal computer, or any other originating device to one of four receivers.   __ Circuit Design by James Dean, National Research Council, Ottawa, ON, Canada

Simple  Touch-Sensitive Switch -  This touch-sensitive switch is built around NAND gate IC CD4011 and transistor BC547.  When someone touches plate 1 (which is connected between pin 1 of gate N1 and ground) , the RS flip-flop__ Electronics Projects for You

Simple Circuit keypad operated switch -  I have modified the design to reduce the complexity of the circuit - and the number of components required.  As a result - the code is somewhat less secure.  However, there should be lots of situations where it will still be adequate.   __ Designed by Ron J

Simple Circuit optical switch -  The 555 is proved to be the most versatile and ubiquitous IC all over the world. This is a possible use: simple inverting schmitt trigger.  When the phototransistor is stroken by IR light it conducts and the voltage between the 1Mohm resistor (arbitrary) and the phototrans drops from VCC to lower values.  When the voltage drops lower than VCC/3 the 555 is triggered and goes high (from 0 TO VCC). __ Designed by Jonathan Filippi

Simple Circuit Voltage Switch for Car Sensors -  This Simple Voltage Switch can be used anywhere you want a relay to switch when a voltage reaches a preset level.  it has lots of applications in cars but can be used in any application where you have 12V DC available.  Having switched the relay on, it will then switch if off as the voltage being monitored drops below the preset level.__ SiliconChip

Simple Mosfet Switch -  Constructing a MOSFET switch is one of the basic level electronics projects and could be useful for beginners to get a hang of the various FET transistors.  The aim of this project is to make control a heavy duty DC load by constructing a simple switch.  MOSFET transistors are capable of handling a large voltage__ 

Simple Relay Circuit -  The following schematic illustrates the Simple Relay Circuit Diagram.  When the switch S is closed in a relay circuit, current flows in the coil, causing a strong magnetic field around the coil.  The soft iron bar in the lamp circuit is attracted toward the right end of the electromagnet and makes contact with the conductor__ 

Simple Relay Step-Up Circuits -  Have you ever needed to power a 12-volt relay in a circuit but only had 6 or 9 volts available? This simple circuit will solve that problem.  it allows 12-volt relays to be operated from 6 or 9 volts, or 24-volt relays from 12 volts.  While most normal relays require the manufacturer-specified coil voltage to__ 

Simple Under-Voltage Cut-Out -  Sensitive low-current relay coils often operate at much lower voltages than their typical ratings.  This can be undesirable in some applications, where low supply voltages can result in erratic system behaviour.  in some instances, this problem could be overcome simply by inserting an appropriate value zener diode in series with the relay coil.  This reduces__ 

Single Control Switch for Fan & AC -  Here is an electronic switch that can be used to switch on both the air-conditioner as well as fan of your room, one by one.  The circuit consists of power supply and__ Electronics Projects for You

Single Output 120VAC 200 Watt 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 David Johnson P.E.-February, 2010

Single processor pin controls on/off function -  29-Apr-04 EDN Design Ideas:  A recent Design ideas prompted me to offer the simpler solution that I used in a recent project (Reference 1].  We needed a momentary power switch with processor supervision.  This supervision would allow the processor to delay a power-down request from a press of the power switch until all routines exited properly __ Circuit Design by Michael Sirkis, Radio Systems, Logan Township, NJ

Single switch controls digital potentiometer -  02/27/02 EDN Design Ideas:  The control of electronic potentiometers in most today's applications comes from controller-generated signals.  However, a significant number of applications exist that require adjustments using manual, front-panel controls.  The circuit in Figure 1 uses one IC , one switch, and 10 discrete components __ Circuit Design by Chuck Wojslaw and Gary M Craig, Catalyst Semiconductor, Sunnyvale, CA

Single switch selects one of three signals -  2-Mar-06 EDN Design Ideas:  Total cost is less than $1 - Low-cost, easy-to-use design allows monitoring of peripherals, sensors.   __ Circuit Design by Felix Matro, JL Audio Corp, Phoenix, AZ

Single switch serves dual duty in small, microprocessor-based system -  03/30/06  EDN Design Ideas:  Low-cost, easy-to-use design allows monitoring of peripherals, sensors __ Circuit Design by Steve Hageman, Windsor, CA

Single-IC-based electronic replaces mechanical switch -  03/15/07 EDN Design Ideas:  Flip-flops debounce pushbutton switch - sample and inexpensive electronic circuit uses a low-cost pushbutton switch to toggle the electrical power on and off.  The circuit replaces a more costly and bulky push-push mechanical swit __ Circuit Design by Santosh Bhandarkar, Bangalore, India

Single-wire keypad interface frees microcontroller-I/O pins -  31-Mar-05 EDN Design Ideas:  Using this interface topology, you can reduce the number of keypad interface wires to just one and thus save critical microcontroller i/O ports __ Circuit Design by Israel Schleicher, Prescott Valley, AZ

Sink to Source Universal DC Converter -  As illustrated below, many control systems use an open collector transistor to turn something on.  Perhaps it is a LED light, a relay or a small motor.  However there are other systems which require a common ground connection instead of a common V+ supply connection . . . Circuit by Dave Johnson P.E.-March, 2011

Six-way Switch -  The 40106 is a versatile CMOS IC containing six Schmitt trigger inverters.  it can be used to implement a set of alternating-action switches with hardware contact bounce suppressionmust register on this site __ Designed by Published in Elecktor July/Aug, 2010

Slave Switcher -  There are many situations where two or more pieces of equipment are used together and to avoid having to switch each item on separately or risk the possibility of leaving one of them on when switching the rest off, a slave switch is often used.  __ 

Sleep Switch Cum Wake Up Timer -  Here is a sleep-switch circuit that can be easily converted into a wake-up timer.  A dual-mode time setting makes the system versatile.  The circuit is low-cost and can function as a__ Electronics Projects for You

Sleeping Aid -  Based on electromagnetic-field radiation; Place it under the pillow - Built-in timer __ Contact Flavio Dellepiane, fladello @ tin.it

Small Pushbutton Controls 10 Amps AC -  The circuit below uses a pair of long lasting lithium coil cell batteries to power a latching relay circuit.  With each activation of the small pushbutton, the relay is either latched closed or unlatched open.  Since coin cells canít provide the necessary peak current, a 500uF capacitor is used to store the needed energy.  The circuit standby current is kept very low by using a stack of five 100uF ceramic capacitors instead of the usual electrolytic cap . . . Circuit by David Johnson P.E.-January, 2012

Smart Exhaust Fan Switch -  Exhaust fans in washrooms can be connected to the lighting circuit so that these switch on and switch off with the electric light.  But as washrooms are sometimes used only for__ Electronics Projects for You

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Got Designs?
Please eMail
if you want me to link to and/or post your original design Thanks.


Switches:  #'s - C       D - L       M - Q       R - S       T - Z


HOME Schematics Index Hobby Corner Dave's Circuits Electronic Resources Contact Info
Imagineering Ezine    Discover Solar Energy Dave Johnson & Associates Faraday Touch Switches


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