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Switch Circuits page 1
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Last Updated on: Tuesday, April 01, 2014 04:30 AM

Circuits Designed by Dave Johnson, P.E. :
  • 12v Light/Dark Switch 
    Often, for certain low voltage lighting systems; you would like to turn off the lights during the bright light of the day.  Most commercial day/night switches are designed for AC lighting.  The circuit below was designed for a 12v DC system.  But, it could be modified for other voltage as well.  It uses an inexpensive phototransistor as the light detector.  An n-channel FET is used to switch power to the lights.  A transistor circuit is included to provide some hysteresis.... 

  • 12v – 24v AC and DC Day/Night Switch
    The circuit uses a bridge rectifier circuit to convert AC into DC.  A 12v zener diode limits the operating voltage of the circuit to 12v.  A tiny Schmitt trigger inverter and a phototransistor detects the ambient light intensity.  If there is sufficient light, the inverter disables a push-pull oscillator circuit.  The oscillator, with a differential output, drives a charge pump circuit which when activated, provides sufficient gate-source voltage to a pair of n-channel FETs to turn them on fully.  The transistor switch can handle both AC and DC with a current in excess of 5 amps.
    ....
  • 120VAC Touch Switch
    This is a capacitance based touch on/touch off switch, which can control power to a 200 watt 120vac load.  (added 12/04)

  • 24vac Powered Day/Night Switch
    Many low voltage outdoor lighting systems use 24vac to power the devices.  The low voltage is much safer to use outside than standard 120vac or 240vac power systems.  The circuit below is designed to turn off power to outdoor lights during daylight and turn them back on at night.  The circuit uses a phototransistor to detect daylight.  I would suggest you use a phototransistor which has a built in daylight filter. These are colored a deep purple. The filter helps insure the circuit reacts only to sunlight....

  • 240VAC Touch Switch
    This is another capacitance based touch on/touch off switch, which can control power to a 200 watt 240vac load.  (added 12/04)

  • Audio Activated Switch
    This switch circuit is powered for years by a single 3v lithium cell.  Its transistor switch closes whenever the circuit detects audio signals in excess of 50mv RMS.  It can be used to trigger relays or activate indicator lights.  (added 12/04)

  • Audio Signal Detector Switch
    This circuit will activate a transistor switch when it detects at least 50mv peak to peak of an audio signal.  It could be used to turn on a relay, routing the signal to were it is needed.  (added 7/06)

Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:
µC implements Pushbutton Light Dimmers -  06/18/98 EDN-Design Ideas....A project required building a synchronous-demodulator circuit to track a line drawn on paper.  beauty of  synchronous-modulator/demodulator approach is its inherent noise rejection.  method rejects ….File contains several circuits, scroll to find this one.... [Design Idea by William Grill, Riverhead Systems, Littleton, CO]
µC Provides Wireless Keypad Control -  10/08/98 EDN-Design Ideas....Portable systems, such as telephone handsets, make extensive use of low-dropout (LDO]regulators. se components provide noise-sensitive parts with a stable power-supply line....Scroll to find this specific article.... [Design Idea by Lloyd Khuc, Motorola Inc, Austin, TX]
1 oscillator drives multiple solid-state relays -  16-Mar-06 Issue of EDN  A conventional electromechanical relay often makes sense for switching large amounts of load current on and off and when proportional control of the load’s current or voltage is unnecessary.... [Design Idea by Juan Ramón Vadillo Pastor, SOR Internacional SA, Saint Quirze Del Valles, Barcelona, Spain]
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. …. [Designed by David A. Johnson]
10 Reasons to Upgrade to a 16100% or 16900 Series Logic Analyzer  -  ....application note is....internal Xilinx and....packet level to....buses ...4 3....integrity by quickly....Trace Core) core....Interface, POS PHY....Agilent Application Note  2007-12-03....[App Note]
100 Seconds Duration On Switch with Touch Control -  This is a touch control switch which keeps the circuit on about 100 seconds after touching the plate connected to the 2 numbered pin. At the end of this time duration, relay releases and the circuit gets to off position. The impedance of the trigger input of the 555 timer IC is very high and the inductive voltage on the human body is enough to trigger it. The circuit works based on this principle. You can use a piece of metal as a plate. The circuit can be used in toy circuits, buzzers or any project that is suitable. You can adjust the duration time by changing the R1 and C1 values. …....
120VAC Touch Switch -  This is a capacitance based touch on/touch off switch, which can control power to a 200 watt 120vac load.  (added 12/04) …. [Designed by David A. Johnson]
12v Light/Dark Lamp Switch -  At night, this circuit will route current to a 12v lamp, turning it on.  (added 7/06) …. [Designed by David A. Johnson]
12v Light/Dark Switch -  Often, for certain low voltage lighting systems; you would like to turn off the lights during the bright light of the day.  Most commercial day/night switches are designed for AC lighting.  The circuit below was designed for a 12v DC system.  But, it could be modified for other voltage as well.  It uses an inexpensive phototransistor as the light detector.  An n-channel FET is used to switch power to the lights.  A transistor circuit is included to provide some hysteresis. This keeps the circuit from fluttering the light during the transition from day to night and night to day.  It is recommended that a plastic tube be placed over the transistor to prevent it from being illuminated by the lights it is controlling.  By selecting the appropriate power FET, the circuit could control over 100 watts worth of 12v lighting. (July 27, 2008) …. [Designed by David A. Johnson]
12v – 24v AC and DC Day/Night Switch - The circuit uses a bridge rectifier circuit to convert AC into DC.  A 12v zener diode limits the operating voltage of the circuit to 12v.  A tiny Schmitt trigger inverter and a phototransistor detects the ambient light intensity.  If there is sufficient light, the inverter disables a push-pull oscillator circuit.  The oscillator, with a differential output, drives a charge pump circuit which when activated, provides sufficient gate-source voltage to a pair of n-channel FETs to turn them on fully.  The transistor switch can handle both AC and DC with a current in excess of 5 amps.....[Circuit of the Week, Designed by David A. Johnson]
2 Way IR Term -  This unit provide 2 way IR communications using a numeric keypad and an LCD display.  Data is sent and recieved in ASCII with no regard to what the data means to any particular device.
….... [Luhan Monat - Mesa Arizona]
2 wire 4 by 4 key keyboard interface saves power -  08/17/06 EDN-Design Ideas....Resistor matrix and microcontroller encode keypad.... EDN is migrating links. This link is not verified.  Google the "title" EDN for new link.
20 Watt Simple Switcher Forward Converter -  National Semiconductor Application Note 01 May1998 (app note added 6/06)
240VAC Touch Switch -  This is another capacitance based touch on/touch off switch, which can control power to a 200 watt 240vac load.  (added 12/04) …. [Designed by David A. Johnson]
250kHz 1mA I Q Constant Frequency Switcher Tames Portable Systems Power -  DN108  Design Notes (Linear Technology) (app note added 1/06)
27MHz AM/CW Transmitter -  Electroinic design circuit…. [from Harry Lythall's website]
3.3V Bus Switches for PC100/PC133 DIMM Switching -  Pericom Semiconductor Application Brief # 032....[App Note]
4 Digit Keypad -  (electronic design added 9/02)
49MHz Walkie-Talkie -  Lots of people are requesting walkie-talkie and RF remote control schematics, so here is some. Building se circuits needs special equipment and expertise in RF circuits. If you are going to experiment with se circuits, please note that I did not build.... [Peter Jakab, Electrical Engineer, Engineer of Informatics]
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.... [Designed by David A. Johnson]
555 Timer MonoStable Circuit 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.... [Bill Bowden's website]
556 Timer Stall-Motor Switch Machine Drivers -  The circuits on this page are switch machine drivers that can be used to operate Stall-Motor type switch machine motors. The circuits use LM556 dual timer chips to provide a PUSH-PULL output to reverse the polarity of the supply to the switch machine motors. [from Rob Paisley's Model Train web site]
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.... [Designed by David A. Johnson]
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.... [Designed by David A. Johnson]
6 Bit µP's A/D Converter Decodes Keypad's Inputs -  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 provides  key to  savings.  µC's output lines, F1 through F4, energize  keypad's column lines one at a time via 74HC4049 buffer/driver.... [Design Idea by Ryoden International (Shanghai) Ltd, Shanghai, China]
70m Ohm Protected Load Management Switch -  DN117  Design Notes (Linear Technology) (app note added 2/06)
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,.... [Design Idea by Chester Simpson, National Semiconductor, Santa Clara, CA]
8 x 8 Audio Video Switch -  (circuit / design added 8/03) [Peter Jakab, Electrical Engineer, Engineer of Informatics]
A 4-Digit Keypad Controlled Switch -  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've used a SPCO/SPDT relay, but you can use a multi-pole relay if you wish....(electronic schematic added 05/09) [Designer Ron J.]
A Clock Design using the PIC16c54 for LED Displays & Switch Inputs -  Microchip Application Note Published 26-Aug-97....[App Note]
A Simple Method to Reduce DC Power Consumption in CDMA RF Power Amplifiers Through the LMV225 & an Efficient Switcher -  National Semiconductor Application Note....[App Note]
AC continuity tester finds single ended faults in cables -  21-Feb-08 Issue of EDN  A continuity tester injects an AC signal into the conductors of a cable to find circuit faults.... [Design Idea by Kevin Bilke, Maxim Integrated Products, Fleet, Hants, UK]
AC Switch circuit -  An AC triggered switch for low frequency signals…. [Designer Andy Collison]
AC Switching with TRIAC From TTL -  The MC3032 is an optoisolator TRIAC driver. The 180-ohm resistor sets the current for the LED emitter in the optoisolator. Change the value of this resistor, if necessary, to get reasonable current ASCII format  (e.g., 15 mA).  Note that you cannot test this circuit without a load. The TRIAC will not switch unless connected to an AC voltage source, so you can't test it for simple switching w/o applying AC and a load. Note the 500V ating on the .01 cap.  (ASCII format circuit / schematic design added 6/06)
AD5228 Evaluation Kit for the 32-Position, Push Button, Up/Down Control Digital Potentiometer -  AN-712 Analog Devices Application Notes....[App Note]
AD7416/AD7417/AD7418 Power-On Reset Circuit -  AN-588 Analog Devices Application Notes....[App Note]  If a large number of decoupling capacitors are used on  VDD line, re-applying power before VDD has discharged to 0 V can cause  AD7416/AD7417/AD7418 to reset into an unknown. state.
Add a grounded-switch feature for Topswitch on/off control -  21-Jun-07 Issue of EDN  Adding a couple of components to the control pin of a Topswitch switching regulator enables on/off control.... [Design Idea by Robert N Buono, Aeolian Audio LLC, Bloomfield, NJ]
ADG794-a 2.5 V Input Signal Range Swithcing Solution for HDTV -  AN-802 Analog Devices Application Notes  (app note added 2/06)
Advances in High Speed Design in Dispersively Attenuating Environments Circuit Boards & Cables -  ....deals with advances made in methods for....aiding the design and analysis of high performance digital....through dipersively attenuating paths.  Agilent Application Note 2002-04-10   (app note added 06/06/06)
Alternate Action Button -  By pressing S1 momentary  switch, the 4069 hex inverter will cause the relay to turn on. When S1 is pressed again it will cause the relay to go off.  This simple circuit can be used for the bases of many projects. The transistor in the circuit provides enough current to drive the relay…. [Randy Linscott's circuit]
Alternating on/Off Control -  This circuit uses three easily available 555 timer ICs. All three work as astable multivibrators. The first 555 has an on period and off period equal to 1 sec.  This IC controls  on/ off periods of  or 2 555s which are used to flash two bulbs through  relay contacts.... [Tony van Roon's circuit]
AN-1095: Design of Isolated Converters using Simple Switchers -  National Semiconductor Application Note  (app note added 2/06)
AN-1438: A Simple Method to Reduce DC Power Consumption in CDMA RF Power Amplifiers Through the LMV225 & an Efficient Switcher -  National Semiconductor Application Note....[App Note]
AN-213: Low Cost, Two-Chip, Voltage-Controlled Amplifier & Video Switch -  AN-213 Analog Devices Application Notes....[App Note] 
AN-251: Ron Modulation in CMOS Switches & Multiplexers -  AN-251 Analog Devices Application Notes....[App Note]What It Is and How to Predict Its Effect on Signal Distortion
AN-282: Fundamentals of Sampled Data Systems -  AN-282-Analog Device Application Notes....[App Note]
AN-345: Grounding for Low-and-High-Frequency Circuits -  AN-345-Analog Device Application Notes....[App Note]Know Your Ground and Signal Paths for Effective Designs.  Current Flow Seeks Path of Least Impedance-Not Just Resistance....
AN-347: Shielding & Guarding -  AN-347 Analog Devices Application Notes  (app note added 2/06)How to Exclude Interference-Type Noise. What to do and Why to do it-A Rational Approach
AN-348: Avoiding Passive-Component Pitfalls -  AN-348-Analog Device Application Notes....[App Note]The Wrong Passive Component Can Derail Even  Best OpAmp or Data Converter.  Here Are Some Basic Traps to Watch For.
AN-349: Keys to Longer Life for CMOS -  AN-349 Analog Devices Application Notes  (app note added 09/08) Here's How CMOS Can be Protected Against Abuse
AN-354: Ask the Applications Engineer 1-Multi Troubles -  AN-354-Analog Device Application Notes....[App Note]Addresses problems of ten encountered with LOG Circuits, Time Division Analog Multiplexing, and ADC Power Strobing
AN-355: Behind the Switch Symbol -  AN-355 Analog Devices Application Notes....[App Note]Use CMOS Analog Switches More Effectively When You Consider Them as Circuits
AN-447: Protection Schemes for BI-FET Amplifiers & Switches -  National Semiconductor Application Note  (app note added 2/06)
AN528: Implementing Wake-Up on Keystroke -  Microchip Application Note Published 26-Aug-97  (app note added 2/06)
AN529: Multiplexing LED Drive & 4x4 Keypad Sampling -  Microchip Application Note Published 26-Aug-97  (app note added 2/06)
AN552: Implementing Wake Up on Keystroke -  Microchip Application Note Published 26-Aug-97  (app note added 2/06)
AN586: Macros for Page & Bank Switching -  Microchip Application Note Published 26-Aug-97  (app note added 2/06)
AN-588: AD7416/AD7417/AD7418 Power-On Reset Circuit -  AN-588 Analog Devices Application Notes....[App Note]  If a large number of decoupling capacitors are used on  VDD line, re-applying power before VDD has discharged to 0 V can cause  AD7416/AD7417/AD7418 to reset into an unknown. state.
AN590: A Clock Design using the PIC16c54 for LED Displays & Switch Inputs -  Microchip Application Note Published 26-Aug-97....[App Note]
AN-665: Channel Switching using Σ-Δ ADCs -  AN-665 Analog Devices Application Notes....[App Note]This application note refers to  AD7708 and AD7718. Data sheets specify  update rate for Σ-Δ ADCs.
AN-712: AD5228 Evaluation Kit for the 32-Position, Push Button, Up/Down Control Digital Potentiometer -  AN-712 Analog Devices Application Notes....[App Note]
AN-734: MF2 Compatible Keyboard with COP8 MicroControllers -  National Semiconductor Application Note  (app note added 2/06)
AN-772: A Design & Manufacturing Guide for the Lead Frame Chip Scale Package -  AN-772-Analog Device Application Notes....[App Note]
AN-80-001  Using model PSW-1211 as a SPST switch -  Application Note MiniCircuits.com  (app note added 2/06)
AN-80-004  Using the RSW-2-25P switch -  Application Note MiniCircuits.com  (app note added 2/06)
AN-802: ADG794-a 2.5 V Input Signal Range Swithcing Solution for HDTV -  AN-802 Analog Devices Application Notes  (app note added 2/06)
AN892: Fail-Safe Monitoring & Clock Frequency Switching using the PIC16f684 -  Microchip Application Note Published 16-Dec-03....[App Note]
Analog Switch Acts as DC/DC Converter -  01/20/00 EDN-Design Ideas....Many low-current devices that require 65V supplies can operate reliably in a single 5V power-supply environment if you use an appropriate localized dc/dc converter to generate  -5V bias. Often,  capabilities and advantages of se 5V ICs far outweigh  minor inconvenience and added costs of an additional -5V-converter function. Many.... [Design Idea by John P Skurla, Advanced Linear Devices Inc, Sunnyvale, CA]
Analog switch converts 555 timer into pulse width modulator -  15-Feb-07 Issue of EDN  Added CMOS switch enhances a PWM oscillator.... [Design Idea by Jordan Dimitrov, Tradeport Electronics, Vaughan, ON; Edited by Brad Thompson and Fran Granville, Canada]
Analog Switch Cuts Peak Detector Reset Time -  05/25/95 EDN-Design Ideas....The schematic in Fig 1  is a basic configuration for a unity-gain peak detector using the PKD-01FP monolithic peak detector from Analog Devices. The reset time, tRES, is the time necessary to discharge the hold capacitor CH. tRES  and the acquisition time tACQ are functions of the IC's output-current capability. With CH10 nF, this output-current limitation sets both tRES and tACQ to about 220 �sec.... [Design Idea by Gualtiero Bolognesi, Landis & Gyr, Peschiera Borronmeo, Italy]
Analog switch expands I2C interface -  22-Nov-01 Issue of EDN  Perhaps the most effective way to gain board space and increase component density is to minimize wiring on the board. A widely used architecture that allows such miniaturization is the I2C bus. Comprising only a bidirectional data line, SDA, and a clock line, SCL, this bus requires no chip selects or other additional connections.... [Design Idea by Luca Vassalli, Maxim Integrated Products, Sunnyvale, CA]
Analog switch frees stuck I˛C bus -  26-Jun-03 Issue of EDN  The dual-channel PCA9540 I2C multiplexer often breaks up an I2C or SM bus or allows you to use devices with the same addresses on the same bus. When the PCA9540 initially powers up, it comes up in a state in which both channels are deselected. The I2 C- or SM-bus master can then address the control register in the PCA9540 to select either Channel 0 or Channel 1, connecting the master to the ap.... [Design Idea by Bob Marshall, Philips Semiconductor, Morgan Hill, CA]
Analog switch lowers relay power consumption -  20-Dec-01 Issue of EDN  Designers often use relays as electrically controlled switches. Unlike transistors, their switch contacts are electrically isolated from the control input. However, the power dissipation in a relay coil may render the device unattractive in battery-powered applications. You can lower this dissipation by adding an analog switch that allows the relay to operate at a lower voltage (Figure 1].... [Design Idea by Steve Caldwell, Maxim Integrated Products, Chandler, AZ]
Analysis of NMR/MRI Coils using PIN Diode Switches -  MicroNote 711 from Microsem....[App Note]
AN-H32: HT0640 for Electronic Line Switch -  Supertex Semiconductors  (app note added 2/06)
AN-H39: HT18 & HT19 for Electronic Line Switch -  Supertex Semiconductors  (app note added 2/06)
Anticipating timer switches before you push the button -  3-Apr-03 Issue of EDN  (Editor's note This Twilight Zone-worthy circuit will be the subject of an upcoming network sitcom, My Big Fat Anticipating Timer.] It happens to almost everyone that an apparatus or system should have been turned off a moment ago. The device in question could be the car heater, the air conditioner, the lights.... [Design Idea by Jean-Bernard Guiot, DCS AG, Allschwil, Switzerland]
Ask the Applications Engineer 1-Multi Troubles -  AN-354-Analog Device Application Notes....[App Note]Addresses problems of ten encountered with LOG Circuits, Time Division Analog Multiplexing, and ADC Power Strobing
Audio Activated Switch -  This switch circuit is powered for years by a single 3v lithium cell.  Its transistor switch closes whenever the circuit detects audio signals in excess of 50mv RMS.  It can be used to trigger relays or activate indicator lights.  (added 12/04) …. [Designed by David A. Johnson]
Audio Auto Shutoff -  The purpose of this circuit is to automatically turn off any device plugged into its power outlets after a certain period of time. Shutoff is activated by an absences of an audio signal or by a standard timer function.  This unit would be connected to speaker terminals of a stereo system, tape outputs, TV earphone jack or audio outputs etc. Once the audio signal drops below a predetermined level a …. [Randy Linscott]
Audio Controlled Christmas Lights -  Here is a simple circuit to control 110VAC things such as Christmas Lights with low voltage audio. Be careful, high voltage AC can kill you.  “The basic Idea was to have Christmas lights flash with the music. In my design I use an ordinary amplified computer speaker, a diode bridge, and a ‘CRYDOM’ SSR (Solid State Relay). In order to increase the time that the lights were on as well as protect the SSR I used a Diode Bridge to rectify the signal from the amplifier circuit.”....(added 02/09)
Audio Signal Activated Switch -  Drawing only 2uA from a 3v lithium battery, this circuit will turn on a transistor switch, whenever it detects an audio signal greater than 0.035v RMS. [Designed by David A. Johnson]
Audio Signal Detector/Switch -  For some audio systems it is desirable to have an automatic switch circuit turn on other devices, such as an amplifier, if an audio signal is detected on one line.  The hobby circuit below will activate a transistor switch when it detects at least 50mv peak to peak of an audio signal.   The switch could be used to turn on a relay, routing the signal to where it is needed.  A single 3v lithium cell will power the electronic circuit for about 5 years. …. [Hobby Corner Circuit by Dave Johnson]
Audio Video Switch -  This is an 8-input x-output audio/video switch module to be controlled from a computer, for example from  parallel port. Each audio/video output can be switched to any of  8 inputs, separately.1-module drives1-audio/video output and has a34-pin connector to plug into  system interface. You can use video OPA-s on 4051 output instead. Note that you can get full integrated video multiplexers from Maxim.... [Peter Jakab, Electrical Engineer, Engineer of Informatics]
Audio Voice-Over Circuit -  (electronic design added 6/07)
Automatic Headlight Brightness Switch (Aaron Cake) -  Driving the highway with your high-beam headlights can really increase your visibility, but can be a blinding hazard for other drivers.  This simple circuit can be wired into your headlight switch to provide automatic switching between high and low beam headlights when there is oncoming traffic. It does this by sensing the lights of that traffic. In this way, you can drive safely with your high-beams on without blinding other drivers.... [Aaron Cake's design]
Automatic Hen House Door Closer Opener -  Find out how to put together a DIY automatic hen house door opener and closer…. [REUK - Renewable Energy UK website]
Avoiding Passive-Component Pitfalls -  AN-348-Analog Device Application Notes....[App Note]The Wrong Passive Component Can Derail Even  Best OpAmp or Data Converter.  Here Are Some Basic Traps to Watch For.
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 (added 09/05)]
AVR 2x16 LCD & 4x4 keypad driver -  A very simple circuit to experiment with AT90S2313, 2x16 LCD display and 4x4 keypad. The clock based on 4 MHz crystal, but you can use anyone crystal between 1-4 MHz. The keys with the name "A", "B"...."F" are typed to the LCD with numbers 10-16. Because the AVR have only 15 I/O pins we are working the LCD display with 4-bit databus. The 4 resistors (10K) are to protect the AVR from the shortcuts as the coloumn of the keypad is change....(circuits added 05/09)
Behavior of CMOS in hot insertion -  Pericom Semiconductor Application Brief # 039....[App Note]
Big Endian to Little Endian Data Conversion using 3.3V Bus Switches -  Pericom Semiconductor Application Brief # 034....[App Note]
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.... [Design idea 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 trigger’s hysteresis.  [Designed by Andrew R. Morris  (added 6/06)]
Block power switching module -  (circuit added 06/07/08)
Boole helps simplify wiring and save money -  8-Jul-04 Issue of EDN  To safely observe the positions of two cylinders, you need two signals  one circuit, X, which is open only when both cylinders are in a safe position (two normally closed switches in parallel], and one circuit, Y, which is closed only when both cylinders are in a safe position (two normally open switches in series, Figure 1].... [Design Idea by Jean-Bernard Guiot, Mulhouse, France]
Brakelight hookup -  This circuit is NOT a pulser or flasher! What's so special about this circuit? Well, the first third-brake light I installed I had to pull a wire from the Third Brake Light all the way underneath the carpet to the brake-pedal-switch and I thought it would be easier to pluck the signal of both brakelights via the trunk. Bench-test your circuit first and apply power to the circuit,.... [Tony van Roon's circuit]
Buffer switches analog or Digital signals on/off -  03/30/06 EDN-Design Ideas....Use an op amp and a dual SPST to switch signals under digital control  EDN is migrating links. This link is not verified.  Search the "title" + "EDN" for new link.
Build a negative-voltage power side switch -  14-Oct-04 Issue of EDN  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 MIC4451 can assume a different role. It provides complementary, low-on-resistance MOSFET switches to connect a system power-supply rail to a negative input voltage or to ground, enable.... [Design Idea by Michael English, Micrel Semiconductor, San Jose, CA]
Build a simple one-chip phototimer -  8-Jul-04 Issue of EDN  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 dark—in other wor.... [Design Idea by Abel Raynus, Armatron International, Malden, MA]
Build a simple, soft-action muting switch -  14-Oct-04 Issue of EDN  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.... [Design Idea by John Firestone, Bremerhaven, Germany]
Bus Load Isolation using a High Density 3.3V Bus Switch -  Pericom Semiconductor Application Brief # 033....[App Note]
Bus Switch Applications For Laptop Computers; Memory Modules; A/D Video; Etc -  Pericom Semiconductor Application Brief # 013 (app note added 2/05)
Bus Switch for Memory Switching: PI5C16292 -  Pericom Semiconductor Application Brief # 018....[App Note]
Bus Switch in PCI Hot Plug Applications -  Pericom Semiconductor Application Brief # 019....[App Note]

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