Camera Switcher:  This circuit can be used for multiple cameras with one monitor. The circuit can be operated manually or automatically. (added 10/05)

Capacitive Sensor:  Special design for shop-windows animation Useful for many types of touch controls (Circuit added 9/04)

Capacitor Discharge  Switch Machine Power Supplies (E+F):  (Circuit / schematic design added 6/06)

Car Alarm and Immobilizer:  This circuit features exit and entry delays, an instant alarm zone, an intermittent siren output and automatic reset. By adding external relays you can immobilize the vehicle and flash the lights.....  (Circuit / schematic design added 6/06)

Cell-Phone-Controlled Audio/Video Mute Switch:  (Circuit / schematic design added 6/06)

Channel Switching using Σ-Δ ADCs:  AN-665 - Analog Devices Application Notes  (Circuit / schematic design added 6/06)  This application note refers to the AD7708 and AD7718. Data sheets specify the update rate for Σ-Δ ADCs.

Cheap Pushbutton Replaces Rotary Switch:  10/26/00 EDN-Design Ideas / (added 05/02) / The problem of setting any one of four modes of a µC-operated process has a straightforward solution: Have the µC check the states of some 4 bits of a µC register or an input port and then execute one of the four predetermined subroutines according to the result. The next question is how the operator sets these 4 bits or, specifically, selects a desirable mode of operation.
One approach is to use a rotary switch (Figure 1a). This circuit does the job but is rather expensive for consumer applications. You can also....

Circuit efficiently Switches Bipolar LED:  11/22/01 EDN Design Ideas  /  (added 1/05)  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 substantially more than the sum of the LEDs' forward voltages. The circuit is, therefore, marginal, to the point of being unusable, with a 5V supply and a red or green LED, which... ...

Circuit forms DC Motor Switch with Brake:  01/10/02 EDN Design Ideas  /  (added 1/05)  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 removes relay contact Bounce:  11/27/03 EDN Design Ideas  /  (added 1/05)  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 simulates contact bounce :  05/08/97 EDN-Design Ideas  / (added 2/06) 

Clap Activated Remote:  (Circuit / schematic design added 6/06)

Clap Relay:  Clap sensitive on-off Relay.  3V Battery operated, small portable unit, (added 03/05)

Clap Switch:  (Electronic circuit design added 02/05)

Clean Switcher Powers 16 Bit A/D Converters:  07/04/94 EDN-Design Ideas / (Circuit / schematic design added 6/06) The low-noise switcher in Fig 1 works much like a TV's horizontal-deflection circuit to provide clean power for a 16-bit A/D converter. In operation, Q3 is a logic-level gate-drive MOSFET driven by the same 100-kHz square wave that clocks the A/D converter. When Q3 turns off, the primary of T1 resonates with C3 and flies back to 25V. Energy then transfers to the transformer's secondary. When the flyback voltage attempts to go below ground, the integral body diode of the power MOSFET Q3 clamps the flyback voltage, causing excess resonant energy in the transformer to flow back through its primary, recharging C1. While C1 is recharging and the drain of Q3 is nearly at 0V, the gate of Q3 gets turned on again, repeating the cycle....  

Clock Design using the PIC16c54 for LED Displays and Switch Inputs:  Microchip Application Note - Published 26-Aug-97   (Circuit / schematic design added 6/06)

Clock Fail Circuit Switches to Alternate Clock:  10/24/96 EDN-Design Ideas / (Circuit / schematic design added 6/06)  

Clock Switching Circuit Banishes Glitches:  12/19/96 EDN-Design Ideas / (Circuit / schematic design added 6/06)  

CMOS Switches vs. PIN Diode and GaAs Switches :  Application Note - California Eastern Laboratories - Doc #959  (Circuit / schematic design added 6/06)

Cold Activated Switch #2:  A simple thermistor triggered cold switch with adjustable threshold.  (added 10/05)

Cold Activated Switch:  The thermistor used has a resistance of 15k at 25 degrees and 45k at 0 degrees celsius. A suitable bead type thermistor is found in the Maplin catalogue. The 100k pot allows this circuit to trigger over a wide range of temperatures. A slight amount of hysteresis is provided by inclusion of the 270k resistor. This prevents relay chatter when temperature is near the switching threshold of this circuit. (added 2/06)

Combinational Conjuring Trick:  (Electronic Schematic / circuit added 4/02)

Connecting AT90S2313 with LCD Display 2x16 Char and 4x4 Keypad:  (Circuit / schematic design added 6/06)

Contact debouncing algorithm emulates Schmitt trigger:  07/07/05 EDN Design Ideas  / (added 11/05)  Another approach to solving the ubiquitous contact debounce problem.

Controlling a Light with Two Switches:  a light or lights can be controlled by more than1-switch (circuit / schematic added 2/03)

Current Limit Switch is Digitally Programmable:  Maxim Application Notes / 298 / Dec-04  (Circuit / schematic design added 6/06)

Current-Limit Switch is Digitally Programmable:  08/17/00 EDN-Design Ideas  / (Circuit / schematic design added 6/06)    

Dark Activated Switch or Porch Light Switch:  (added 8/03)

Dark activated Switch:  (added 04/05)

Dark-activated 230V Lamp:  Compact circuitry using small-size parts only.  Can be wired in parallel to existing switches. (circuit design added 3/05)

Dark-activated LED or Lamp Flasher:  Simple photo-sensitive circuit - 3V battery supply (Circuit added 9/04)

DC Motor Control using a Single Switch:  (Circuit / schematic design added 6/06)

DC Motor Reversing Circuit #2:  (added 8/03)

DC Motor Reversing Circuit:  (circuit / schematic added 6/05)

DC Push Button Motor Control Circuit:  (added 8/03)

Debouncing Networks Make Reliable Selector:  06/05/97 EDN-Design Ideas / (Electronic Circuit diagram added 03/03)  

Debugging IP Router Subsystems--Logic Analysis Tools for POS, Gigabit Ethernet and ATM:  Agilent Application Note   (Circuit / schematic design added 6/06)

Decimal to BCD Convertor:  This circuit will provide an output in Binary Coded Decimal from any of the input switches. The input switches may be expanded to 16 switches, providing a Hexadecimal to BCD conversion. (added 8/03)

Delayed Off Light Switch :  This is an unusual design in that it uses plain metal gate CMOS logic instead of the usual PIC or a custom chip. The 22uF capacitor charges up during one half of the ac cycle, and supplies trigger current to the triac on both halves.  (added 2/05)

Demonstrating the *set_report* Request: With PS/2® to USB Keyboard Translator Example:  Microchip Application Note - Published 4-May-04   (added 2/06)

Design Guidelines for Contention When using PI5C680X:  Pericom Semiconductor Application Note # 035 (Electronic circuit design added 02/05)

Design Guidelines for Power Sequencing When using PI5C680X:  Pericom Semiconductor Application Note # 032 (Electronic circuit design added 02/05)

Design of Isolated Converters using Simple Switchers:  National Semiconductor - Application Note   (added 2/06)

Designing High-Speed Digital Systems for Logic Analyzer Probing:  Agilent Application Note   (Circuit / schematic design added 6/06)

Designing USB 2.0 Interface using PI3USB20 Switch:  Pericom Semiconductor Application Note # 067 (added 2/05)

Designing with the sTMUx1000l ethernet gigabit lan switch:  AN2248 The device integrates three Single Pole Dual Throw (SPDT) Channels for LED support and is available in two different packages, the TSSOP56 and QFN56. This AppNote highlights various applications into which the STMUX1000L Gigabit LAN Switch can be... (Circuit / schematic design added 6/06)

Differential Driver Doubles as Versatile Rf-Switch Driver :  1/6/05   EDN-Design Ideas / (Circuit / schematic design added 6/06)

Digital Combination Lock:  (Electronic Schematic / circuit added 4/02)

Digital Switching System:  (Electronic Circuit / Schematic added 10/04)

Digital Timer Light Switch :  Typical circuit representative of those used in most light switch type digital timers. The timer module is normally a PIC or custom chip, and it syncs to the AC line so that a trigger pulse can be supplied at the right moment. (added 2/05)

Digitally control room light intensity:  11/11/04 EDN Design Ideas  / (added 11/05)  Many people favor different light and temperature settings for different rooms depending upon their mood or whether they are working or relaxing. The circuit in Figure 1 controls the intensity of the artificial light in a room and monitors the temperature of two zones. The two main circuit blocks are the PIC16C67 master controller and the ADT7516 temperature-sensor interface, which includes a ...

Diode Matrix Systems for Stall Motor Switch Machines:  (Circuit / schematic design added 6/06)

DMX PC keyboard interface:  (Electronic circuit added 4/05)

Dog whistle :  It's well known that many animals are particularly sensitive to high-frequency sounds that humans can't hear. Many commercial pest repellers based on this principle are available, most of them operating in the range of 30 to 50 kHz. From what I've read, dogs and other mammals of similar size behave much differently than insects. They tend to respond best to frequencies between 15 and 25 kHz and the older ones are less susceptible to higher tones. This means that an ordinary pest repeller won't work simply because dogs can't hear it. Therefore, I decided to construct a new circuit (based on the venerable 555, of course) with variable pitch and a relatively loud 82 dB miniature piezo beeper. The circuit is very simple and can be easily assembled in half an hour. Most of the components are not really critical, but you should keep in mind that other values will probably change.... (added 11/05)

Doorbell with Counter:  (Electronic Schematic / circuit added 4/02)

Dual White LED Driver Features Integrated Switches and Schottky Diodes in 3mm × 3mm Dfn Package:  DN1010 -  Design Notes (Linear Technology)  (Circuit / schematic design added 6/06)

Dual-Display with LED Driver with 3/2x Switched Capacitor Boost:  National Semiconductor Application Note LM2796 February 2004 (added 2/05)

Electronic Keypad:  (added 9/02)

Electronic Night Light:  (added 8/03)

Electronic potentiometer system has pushbutton interface:  09/26/02  EDN - Design Ideas / (Circuit / schematic design added 6/06)    As systems grow smaller, it becomes increasingly attractive to replace mechanical potentiometers with electronic potentiometers, which are smaller and less expensive silicon equivalents. A common interface for such devices comprises a Chip-Select, Increment and, Up/ line. CS activates the device and, on a rising edge of steps the wiper in a direction that the U/ pin indicates..

Evaluation Kit for the 32-Position, Push Button, Up/Down Control Digital Potentiometer:  AN-712 - Analog Devices Application Notes  (Circuit / schematic design added 6/06)

Excessive Current Consumption Reduction for Switches with Undershoot:  Pericom Semiconductor Application Brief # 043 (Electronic circuit design added 02/05)

Fail-Safe Monitoring and Clock Frequency Switching using the PIC16f684:  Microchip Application Note - Published 16-Dec-03   (Circuit / schematic design added 6/06)

Fault latch circuit protects Switchers:  02/19/04 EDN Design Ideas  /  (added 1/05)  Many power-supply designers like to have a regulator latch off in the event of an overcurrent situation or other fault condition. Yet, many PWM controllers do not internally support this latch-off function. Most do, however, have a power-good output and an enable function. The circuit in Figure 1 adds that latch-off capability at low cost in little additional space....

Four Digit Keypad:  (added 9/02)

Frequency Switch:  (Electronic circuit added 4/05)

Fridge Door Alarm:  (Circuit added 9/04)

Frost Alarm:  The thermistor used has a resistance of 15k at 25 degrees and 45k at 0 degrees celsius. A suitable bead type thermistor is found in the Maplin catalogue. The 100k pot allows this circuit to trigger over a wide range of temperatures. A slight amount of hysteresis is provided by inclusion of the 270k resistor. This prevents relay chatter when temperature is near the switching threshold of this circuit. (added 2/06)

Fundamentals of Sampled Data Systems:  AN-282-Analog Device Application Notes  (added 2/06) 

Garden Light Switch:  (added 8/03)

Grounding for Low-and-High-Frequency Circuits:  AN-345-Analog Device Application Notes  (added 2/06)  Know Your Ground and Signal Paths for Effective Designs.  Current Flow Seeks Path of Least Impedance-Not Just Resistance....