PCMCIA Socket Voltage Switching Design Note 93:  DN93 -  Design Notes (Linear Technology) (app note added 6/06)

Perimeter Monitor:  Using a single cable such as speaker wire or doorbell cable, this circuit can be remotely positioned, for example, at the bottom of a garden or garage, and used to detect all sound in that area. The cable can be buried in a hosepipe or duct and is concealed out of sight. The mic is an ordinary dynamic mic insert and should be housed in a waterproof enclosure with the rest of the circuit. (added 4/02)

Photovoltaic Switch disables unused LEDs:  02/05/2004  EDN-Design Ideas  In low-noise analog circuits, a high-gain amplifier serves at the input to increase the SNR. The input signal level determines the input-stage gain; low-level signals require the highest gain. It is also standard practice in low-noise analog-signal processing to make the circuit's bandwidth as narrow as possible to pass only the useful input-signal spectrum. (added 10/05)

Pine Racecar Victory Judge:  (circuit / schematic added 6/05)

PINs and GaAs MESFET Switches-Effects On Linearity:  MicroNote 703 from Microsem  (app note added 6/06)

Porch light slave switch:  This circuit turns on the porch light when a passive IR security light is activated.  Designed by Andrew R. Morris  (added 09/05)

POS-PHY Level 4 SystemIO Cores by Xilinx (Speaker Notes):  Agilent Application Note   (app note added 6/06)

POS-PHY Level 4 SystemIO Cores by Xilinx:  Agilent Application Note   (app note added 6/06)

Printer Port Activates CMOS Switches:  05/02/02 EDN Design Ideas  /  (added 1/05)  The cost-effective design in Figure 1 provides control for CMOS switches without the need for an external power supply. Analog switches such as those in the MAX4663 are ideal for use in low-distortion applications. They are preferable to electromechanical relays in automatic test equipment or other applications in which you need current switching....

Protection Schemes for BI-FET Amplifiers and Switches:  National Semiconductor - Application Note   (app note added 2/06)

Protection standards applicable to switching equipment:  AN583  (app note added 6/06)

Push Button Switch Debouncer:  (circuit / schematic added 6/05)

Pushbutton Switch Controls Power Supply and µC:  09/25/97 EDN-Design Ideas / (added 6/06)  Switching handheld units on and off with a pushbutton switch is a desirable feature. Thus, switching-regulator/ controller ICs for battery-powered applications provide a logic input to switch the device to a shutdown mode. This type of shutdown pin can require additional components and logic gates to implement the pushbutton interface. However, a simple circuit can implement an on/off function with no external logic (Figure 1). The circuit is based on IC1's step-down controller, which provides the toggle on/off function internally with a SET/RESET latch. Momentarily grounding the ON pin sets the latch and turns on the regulator; momentarily grounding the LBI/OFF pin resets the latch and turns off the regulator....  

Pushbutton Switch Debouncer:  (electronic (schematic / circuit added 4/02)

Pushbuttons and digital potentiometer control boost converter:  02/17/05 EDN Design Ideas  / (added 11/05)  Digitally controlled potentiometers are useful for generating analog control voltages under the control of a microcontroller. In some applications, manual pushbutton switches could replace a microcontroller and simplify product design. Mechanical switches exhibit contact bounce, and, when a user actuates them, they may open and close many times before reaching a stable state.

Quickly discharge Power supply capacitors:  07/05/01 EDN Design Ideas  /  (added 1/05)  A perennial challenge in power-supply design is the safe and speedy discharge, or "dump," at turn-off of the large amount of energy stored in the postrectification filter capacitors. This energy, CV 2 /2, can usually reach tens of joules. If you let the capacitors self-discharge, dangerous voltages can persist on unloadded electrolytic filter capacitors for hours or even days....

Radio Controlled 3way Light Switch :  (electronic design / schematic added 2/05)

RC Receiver hosts two independent Switches:  06/06/96 EDN Design Ideas  / (added 8/05)  Typical inexpensive radio-control (RC) systems have servo-motor outputs, but no on/off switch outputs. You can add two independent RC switches to a system without making any transmitter or receiver modifications.

Relay driver saves substantial power :  07/02/98 EDN-Design Ideas  / (added 6/06)   It is common practice to operate relays and solenoids at a reduced holding power once the mechanical actuation takes place. Relays are usually specified to pull in within 3 msec at 80% of the rated voltage and to release at 30% of the rated voltage. The circuit in Figure 1 drives as many as eight 12V (Ž120V coil) power relays, which memory-map into an 8-bit mP bus. An octal latch stores the relay status, where each bit of the 8-bit word....

Relay Toggle Circuit using a Dual 555 timer (556): This is probably the best toggle circuit.:  (circuit / schematic design added 6/06)

Relay Toggle Circuit using a Single Transistor and Push Button:  (circuit / schematic design added 6/06)

Remote Control turns Battery on and Off:  09/12/97 EDN-Design Ideas / (added 4/05)  

Remote Doorbell Indicator:  (circuit / design added 8/03)

Remote Doorbell Warning Switch:  This circuit should only be used with the solenoid type chime doorbells, the electronic type that play tunes will not work here. The hardest part for this circuit was the title. It is quite easy to miss the sound of a doorbell if you are watching TV , this circuit gets round the problem by providing a visual indication, i.e. a lamp. As an alternative, a LED could also be used. You could just parallel a lamp across the doorbell, but this would mean extra drain from the doorbell batteries or transformer. (added 2/06)

Remote Switch uses No Power Fiber Optic Link:  10/10/96 EDN-Design Ideas / (added 4/05))  

Route Control for Stall Motor Switch Machines:  (circuit / schematic design added 6/06)

RS-232 DB-9 Switch-to-Flip between Two Serial Ports:  (circuit / schematic design added 6/06)

RS-232c Powers and Reads 8 Bit Switch Matrix:  04/11/96 EDN-Design Ideas  / (added 6/06)      

RS-232C Serial Port Scans Remote Keypad:  12/04/97 EDN-Design Ideas / (added 3/03)  

SB-100: Subscriber Line Card for Central Office Telephone Switching Equipment:  National Semiconductor - Application Note   (app note added 6/06)

Scalable latch requires no capacitors or clock:  08/19/04 EDN Design Ideas  /  (added 10/05)  Circuits that latch one-of-N switches usually use a digital approach. Such circuits are often useful in human-interface situations, such as audio-mixing consoles, video-feed selection, or current-loop-control redundancy systems. In high-precision analog systems, such as high-fidelity audio or video, elimination of clocking circuits, whenever possible, reduces the chances of coupling noise back ......

Scheme improves on Low cost keyboard:  10/30/03 EDN Design Ideas  /  (added 1/05)  You can easily improve on a previous Design Idea 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....

Security Circuit Eschews Sophistication:  05/26/94 EDN-Design Ideas / (added 3/03) Because of the many states involved in implementing sequential combination locks, most designers use a microcontroller or a PLD. But for those die-hard discrete designers who don't want to bother with debugging programs, here's a dead-simple circuit that verifies a security code's entry from a 10-digit keypad.....

Ser-Key 10-Key Serial Keypad Encoder:  (circuit / schematic added 6/05)

Shielding and 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

Signal Detecting Auto Power on Unit:  (circuit / design added 8/03)

Simple Method to Reduce DC Power Consumption in CDMRF Power Amplifiers Through the LMV225 and an Efficient Switcher:  National Semiconductor - Application Note   (app note added 6/06)

Simple MIDI Switcher:  (circuit / schematic added 6/05)

Single Processor Pin Controls On/Off Function:  04/29/04 EDN Design Ideas  /  (added 1/05)  A recent Design Idea 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....

Single Switch Controls digital potentiometer #1:  02/07/02  EDN - Design Ideas / (added 6/06)    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. .

Single Switch Controls digital potentiometer #2:  09/19/02  EDN - Design Ideas / (added 6/06)   This Design Idea is an evolution and simplification of another (Figure 1, Reference 1). Replacing the three inverted-input NOR gates with their logical equivalents, positive-input NAND gates, makes these three gate symbols consistent with the fourth, which was drawn as a positive-input NAND gate. The 74HC132's data sheet describes the device as a quad, two-input NAND gate with hysteresis..

Single switch selects one of three signals:  3/2/06  EDN - Design Ideas  /  (added 10/06)  Total cost is less than $1.

Single switch serves dual duty in small, microprocessor-based system:  3/30/06  EDN - Design Ideas  /  (added 10/06)  Low-cost, easy-to-use design allows monitoring of peripherals, sensors.

Single wire keypad interface frees microcontroller I/O pins:  03/31/05 EDN Design Ideas  / (added 5/05)  Using this interface topology, you can reduce the number of keypad interface wires to just one and thus save critical microcontroller I/O ports.

Sleep Switch Cum Wake up Timer:  (circuit / schematic design added 6/06)

Sleeping Aid :  Based on electromagnetic-field radiation Place it under the pillow-Built-in Timer (added 9/04)

Slot Termination Components for Pentium II and Xeon Processor-Based Multiprocessor Systems:  Pericom Semiconductor Application Brief # 026 (app note added 02/05)

Smart Foot Switch:  (electronic Circuit / Schematic added 10/04)

Smart switch cuts transformer turn on Current :  04/23/98 EDN-Design Ideas / (added 11/05) [Note:  File contains multiple circuits - scroll to find this circuit.]  Transformer-core saturation can cause inexplicable fuse blowing, system crashes, or premature switch and relay failure. When a core saturates, it loses its inductive characteristics; primary winding current can then reach extremely high values for several ac cycles. Turning on a transformer may seem fundamental, but in some power-supply designs and control applications, it can be a game of Russian roulette. Because transformers remain polarized when turned off, saturation occurrence is a function of the polarity and phase angle of the ac cycle when you switch the circuit on and off. The smart-switch circuit in Figure 1 eliminates saturation, improves relay reliability, and provides a tool for determining transformer and relay performance....

Soft ON/OFF switch #2:  Modern electronic equipment incorporate "push-to-on-push-to-off" switches that do not make the clicking noise as with old equipment. An example of this is the power button on a ATX computer cabinet. Here is a circuit that does the same. It can be used to turn on/off any electronic/electrical equipment that operates on any range of voltages.  When the "ON/OFF" button is pressed once, the equipment goes on and stays on. It goes off when the button is pressed again. The circuit is straight forward. It uses a JK CMOS FlipFlop to with its JK terminals tied high to achieve the toggling action. The clock is provided by the push button used for on/off action. The resistor and the capacitor near the on/off switch debounces the contacts.  Note that when the circuit is switched on, the relay may land in a on or off state. It can be brought to the off state by pressing the RESET button.  Care should be taken that the relay's current does not exceed 100mA.  Since the IC is CMOS, it can be operated from 3V to 15V, but in this circuit it is operated at 9V for a 9V relay. The relay circuit needs to be modified for other operating voltages.  (added 10/05)

Soft on/Off Switch:  Modern electronic equipment incorporate "push-to-on-push-to-off" switches that do not make the clicking noise as with old equipment. An example of this is the power button on a ATX computer cabinet. Here is a circuit that does the same. It can be used to turn on/off any electronic/electrical equipment that operates on any range of voltages. FAIR WARNING -- THIS SITE HAS ANNOYING POP UP ADS. (added 5/02)

Solid State Relay Saves Battery's Life:  09/01/94 EDN-Design Ideas / (added 5/02)  The circuit in Fig 1 uses a low-resistance p-channel FET, Q4, to disconnect a load from the battery when the battery's voltage drops below a certain value. After you disconnect the circuit, it remains off until you remove and replace the battery. 

Solid State Switch for DC Operated Gadgets:  (electronic Circuit / Schematic added 10/04)

Sound Activated Toy :  This circuit makes a flower bop to the beat of music. The flower stem contains a crooked wire which is spun by the motor. The circuit is a microphone driven peak-detecting one-shot and works very well. The microphone is in a sponge mount to insulate it from the vibration of the running motor. Similar circuits are used to drive rock'n coke cans  (added 2/05)

Sound Operated Switch #2:  (electronic (schematic / circuit added 4/02)

Sound Operated Switch:  This sensitive sound operated switch can be used with a dynamic microphone insert as above, or be used with an electret (ECM) microphone. If an ECM is used then R1 (shown dotted) will need to be included. A suitable value would be between 2.2k and 10kohms. The two BC109C transitors form an audio preamp, the gain of which is controlled by the 10k preset.  The output is further amplified by a BC182B transistor. To prevent instability the preamp is decoupled with a 100u capacitor and 1k resistor....  (added 2/06)

Switch Circuits:  collection of Switch Circuits for temperature, light level and button controlled switching (added 5/02)

Switch debouncer uses only one gate:  05/30/02  EDN - Design Ideas / (added 10/03)    The circuit in Figure 1 produces a single debounced pulse each time you press S1. Moreover, the circuit uses only logic power from the remote pull-up resistor, R2. You can use the circuit to detect when a key is pressed in a nonenergized device, such as a device in a system that's just coming up from standby

Switch De-bouncer Using a 555 Taken from Forrest Mims Mini Notebook.:  (circuit design added 10/06)

Switch Intelligently Controls Current:  03/30/00 EDN-Design Ideas / (added 6/06) - This circuit can intelligently control ac or dc current when connected in series with a load