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Last Updated: October 18, 2017 05:04 AM
Circuits Designed by Dave Johnson, P.E. :
Band Drummerís Microphone Switch -  I received an email from guy who plays drums for a small band.  He wanted a simple way to turn on and off his microphone with just a tap of his drum stick onto a small box.  The circuit below performs this task with the aid of a piezo device as a shock sensor and a small dual coil latching relay with two sets of contacts.  The contacts can be wired any number of ways to a microphone circuit . . . Hobby Circuit designed by David Johnson P.E.-October, 2011

Basement Remote Doorbell -  This circuit will activate a beeper alarm whenever the AC line voltage is less than 100vac . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2006

Capaciatance-Based Touch Switch -  This is another capacitance based touch on/touch off switch, which can control power to a 200 watt 240vac load . . . Hobby Circuit designed by David A. Johnson P.E.-February, 2002

Capacitance Proximity Switch-3 volts -  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 . . . Hobby Circuit designed by David Johnson P.E.-February, 2002

Capacitance Touch Activated Momentary Switch-5v -  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 . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2000

Capacitance Touch 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 . . . Hobby Circuit designed by David A. Johnson P.E.-January, 2002

Car Ignition 12v Switch -  A Discover Circuits visitor needed a way to redirect +12v DC in his car to some auxiliary loads whenever the carís engine was running.  Many cars have cigarette lighter outlet jacks, which are either live all the time or become live when the carís engine is running . . . Hobby Circuit designed by David A. Johnson P.E.-February, 2012

Circuit Protects from Battery Polarity Reversal -  This simple circuit can protect a sensitive electronic circuit from an accidental connection of a battery with a reversed polarity.  The N-channel FET connects the electronic device to the battery only when the polarity is correct.  The circuit shown was . . . Circuit by Dave Johnson P.E.-March, 2002

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

Auto Switch-off Staircase Light -  This site timed-out when I tried to load it.   __ Designed by Harry Lythall-SM0VPO

Auto Turn-Off Battery Charger -  This charger for series-connected 4-cell AA batteries automatically disconnects from mains to stop charging when the batteries are fully charged.  it can be used to charge partially discharged cells as well.__ Electronics Projects for You

Automated USB controlled Power Switch -  Power for TV and set top box (STB) is derived from a common switchboard.  The switched-mode power supply (SMPS) of the TV continues to draw a small amount of power from mains and the STB is not switched off when you switch off the remote.  This next project presents a circuit that can control mains power of an LED TV and the DTH STB.  it also protects the devices from harmful initial surges when power comes back after a power failure. __  Electronics For You

Automatic Bike Headlight Switch -  improved bike headlight switch circuit presented here has been designed to switch bike headlight on (or similar loads) at a presettable ambient light level.  The circuit is based on the renowned timer chip LM555 (IC 1) , here triggered by a decrement in ambient light level.  Here is a 220V automatic light switch, just in case you __ Designed by T.K. Hareendran

Automatic Hen House Door Closer Opener -  Find out how to put together a DiY automatic hen house door opener and closer.   __ Designed by REUK-Renewable Energy UK website

Automatic Mains Disconnect -  Downloading and CD-burning programs usually provide the option of automatically shutting down the PC on completion of their tasks.  However, this energy-saving feature is of little benefit if even after the PC has been switched off, all of the peripheral equipment remains connected to the mains and happily consumes watt-hours.  The circuit shown here provides __ 

Automatic Power Switch -  This circuit turns a slave device on when a master device is turned off or on depending on  state of S1.  The circuit is designed to be reliably and solidly on or off.  Some simpler slave switches can mistrigger or trigger partially,  __ Designed by Andrew R. Morris

Automatic Soldering Iron Switch -  Quite often, we forget to turn off the soldering iron.  This results in not only a smoking oxidised iron but also waste of electricity.  To solve this problem, hereís a circuit__ Electronics Projects for You

AVR 2x16 LCD & 4x4 keypad driver -  Connect some 2x16 characters LCD display and 4x4 keypad with AVR microcontroller __ Designed by © Vassilis Serasidis

Band Drummerís Microphone Switch -  I received an email from guy who plays drums for a small band.  He wanted a simple way to turn on and off his microphone with just a tap of his drum stick onto a small box.  The circuit below performs this task with the aid of a piezo device as a shock sensor and a small dual coil latching relay with two sets of contacts.  The contacts can be wired any number of ways to a microphone circuit . . . Hobby Circuit designed by David Johnson P.E.-October, 2011

Basement Remote Doorbell -  This circuit will activate a beeper alarm whenever the AC line voltage is less than 100vac . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2006

Bipolar transistor boosts switcher's current by 12 times -  05/24/01 EDN Design Ideas:  The circuit in Figure 1 uses a minimal number of external parts to raise the maximum output current of a 0.5A buck switching-regulator IC to more than 6A.  The circuit accommodates input voltages of 15 to 60V and delivers output voltages of 3.3, 5, or 12V, depending on your choice of IC PDf has several circuits, scroll to find this one __ Circuit Design by Wayne Rewinkel, National Semiconductor Corp, Santa Clara, CA

Bistable Switch -  This circuit shows how to implement a simple bistable (On/Off) switch.  You can also do this with a Schmitt trigger gate or inverter.  Just set R1 and R2 to bias  input to  center point of  Schmitt triggerís hysteresis.   __ Designed by Andrew R. Morris

Bit-Switch -  This micro sized servo signal On-Off decoder can be used in any application where size and weight are critical. __ Designed by T. Black

Bounceless switch with NOR gate -  bounceless switch which use NOR gate CMOS CD4001__ 

Buffer switches analog or digital signals -  30-Mar-06 EDN Design Ideas:  Use an op amp and a dual SPST to switch signals under digital control __ Designed by Liviu Pascu, Kepco, Flushing, NY

Build a negative-voltage power-side switch -  14-Oct-04 EDN Design Ideas:  When you need to quickly connect a negative power supply under logic control, the negative power-side switch in Figure 1 can help.  Although originally intended for driving the gates of high-current MOSFETs, the MIC 4451 can assume a different role.  it provide as complementary, low-on-resistance MOSFET switches to connect a system power-supply rail to a negative input voltage or to ground, enable __ Circuit Design by Michael English, Micrel Semiconductor, San Jose, CA

Build a Safety Switch Checker -  Simple unit that lets you check that each power point is covered.  it also verifies the earth connection.__ SiliconChip

Build a Simple Circuit one-chip phototimer -  8-Jul-04 EDN Design Ideas:  Recently, I needed to automatically switch on a lamp when it became dark and keep it on for a given time.  Trying not to reinvent the wheel, I looked through what was available on the market, but I could not find an inexpensive device that satisfied the requirement.  Some products worked like a photoswitch, lighting a lamp when it becomes dark and keeping it on while it is darkóin other wor __ Circuit Design by Abel Raynus, Armatron International, Malden, MA

Build a simple, soft-action muting switch -  14-Oct-04 EDN Design Ideas:  The circuit in Figure 1 adds a soft muting switch with power-up/power-down muting to a line-level audio circuit.  R4, C1, and JFET Q1 quietly ground a signal in 100 to 200 msec when you close S1 or release it when you open S1.  Potentiometer R2, set to twice Q1's cutoff voltage, makes the on/off transition times roughly equal __ Circuit Design by John Firestone, Bremerhaven, Germany

Build a Voice-Activated Relay (VOX) -  Triggers devices on and off with sound.__ SiliconChip

Camera Switcher -  This circuit can be used for multiple cameras with one monitor.  The circuit can be operated manually or automatically.   __ Designed by Milano de Guzman

Camera Trigger -  in 1984 I made a camera trigger to capture transient phenomena.  I had a Mamiya ZE 35mm camera and Mamiyalite ZE flash unit.  Typical for bodies of its time, the only means of remotely triggering the camera was the cable release socket built into its shutter release button.  This was meant to be used with a purely mechanical cable; it let you operate the shutter release from a small distance away, and in a manner that avoided introducing vibration to the camera at the moment a picture was taken __ Designed by John DuBois

Capaciatance-Based Touch Switch -  This is another capacitance based touch on/touch off switch, which can control power to a 200 watt 240vac load . . . Hobby Circuit designed by David A. Johnson P.E.-February, 2002

Capacitance Proximity Switch-3 volts -  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 . . . Hobby Circuit designed by David Johnson P.E.-February, 2002

Capacitance Touch Activated Momentary Switch-5v -  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 . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2000

Capacitance Touch 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 . . . Hobby Circuit designed by David A. Johnson P.E.-January, 2002

Capacitive Touch Switch Uses CPLD -  05/29/08  EDN Design Ideas:  Using an Altera MAX iiZ CPLD, you can implement a touch-switch decoder with no external components __ Circuit Design by Rafael Camarota, Altera, San Jose, CA

Car Door Keypad using LIN network -  Automotive, car and motorcycle electronic circuit diagrams / circuit schematics__ 

Car Ignition 12v Switch -  A Discover Circuits visitor needed a way to redirect +12v DC in his car to some auxiliary loads whenever the carís engine was running.  Many cars have cigarette lighter outlet jacks, which are either live all the time or become live when the carís engine is running . . . Hobby Circuit designed by David A. Johnson P.E.-February, 2012

Cell Phone Controlled Toggle Switch -  Switching Circuits:  When a brief (free) telephone call illuminates the screen of an old mobile phone - the light from the screen operates a simple CMOS 4017 based Toggle Switch.  I used a single-pole relay in the prototype But you can use a multi-pole relay if it suits your application. The Support Material includes A Full Circuit Simulation.  __ Designed by Ron J.

Cheap pushbutton replaces rotary switch -  26-Oct-00 EDN Design Ideas:  The problem of setting any one of four modes of aĶC-operated process has a straightforward solution  Have the ĶC check the states of some 4 bits of aĶC.    __ Circuit Design by Abel Raynus, Armatron International Inc, Melrose, MA

Cheap Sound Sensor for AVR -  I searched the web for a cheap method to let the ATmega respond to sound.  My knowledge in analog circuits is very limited, but what I do remember, is that you can not attach a electret mircophone to a controller pin.  The signal of __ Designed by Alexander Weber

Cheap Touch Switch Using Transistor -  This cheap touch switch circuit is the touch switch is updated from the original version.  Which use IC to control the operation cause difficut for the electronics beginner.  So this circuit is thought to are suitable because uses TR purely.  When was broken also a simple repair.  and More cost-effective equipment.  But The application is__ 

Circuit efficiently switches bipolar LED -  11/22/01  EDN Design Ideas:  The circuit in Figure 1 represents one method to switch a bipolar, two-color LED using an SPDT mechanical switch or relay. This circuit wastes power and does not work properly if the power-supply voltage is not substantiallythan t __ Circuit Design by Spehro Pefhany, Trexon Inc, Toronto, ON, Canada

Circuit forms DC-motor switch with brake -  10-Jan-02 EDN Design Ideas:  Controlling a small dc motor without speed control sounds like a trivial task; a switch or a relay should suffice.  However, several problems accompany this approach.  For one, the switch, because of the inductive load and the low starting resistance of the motor, tends to wear out prematurely (with all the related sparks and EMI problems] __ Circuit Design by JB Guiot, DCS AG, Allschwil, Switzerland

Circuit Project: 12v Touch Switch Exciter -  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.  Circuit diagram Source: DiscoverCircuits__ 

Circuit Project: Doorbell Warning Switch -  This circuit will light a lamp at a remote location when the doorbell switch is pressed.  This circuit should only be used with the solenoid type doorbells, the electronic type that play tunes will not work here.  it is quite easy to miss the sound of a doorbell if you are watching TV , this__ 

Circuit Protects from Battery Polarity Reversal -  This simple circuit can protect a sensitive electronic circuit from an accidental connection of a battery with a reversed polarity.  The N-channel FET connects the electronic device to the battery only when the polarity is correct.  The circuit shown was . . . Circuit by Dave Johnson P.E.-March, 2002

Circuit Removes Relay-Contact Bounce -  27-Nov-03 EDN Design Ideas:  Advances in semiconductor technology have allowed ICs  to replace many mechanical relays, but relays still dominate in high-current circuits that must stand off high voltages of arbitrary polarity.  Contact bounce in those relays, however, can prove troublesome to downstream circuitry.  One approach to contact bounce combines a relay with a hot-swap controller __ Circuit Design by John Guy, Maxim Integrated Products, Sunnyvale, CA

Circuit Simulates Contact Bounce -  05/08/97 EDN Design Ideas:  The circuit in Figure 1a simulates contact bounce of electromechanically and mechanically actuated electrical contacts.  The circuit generates contact-bounce pulses for contact closing and opening.  You can easily program the contact-bounce period and frequency through variable resistors.  This circuit is useful for testing debouncing-hardware circuits and debouncing-software programs __ Circuit Design by John Guy, Maxim Integrated Products, Sunnyvale, CA

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

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Imagineering Ezine    Discover Solar Energy Dave Johnson & Associates Faraday Touch Switches



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