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Switch Circuits

µC Provides Wireless Keypad Control: 10/08/98 EDN-Design Ideas

1.5-V battery-powered fan switches on and off by hand: 07/26/99 Electronic Design - Ideas for Design / This circuit represents a very simple and inexpensive alternative to an electrical switch used to turn ON and OFF the battery-operated dc motor typically employed in handheld fans. It eliminates. . .

2 Line Intercom Plus a Telephone Changeover Switch: The circuit presented here can be used for connecting two telephones in parallel and also as a2-line intercom. FAIR WARNING -- THIS SITE HAS ANNOYING POP UP ADS.

3 Way Touch Lamp: A three-way switch to control a lamp (off-dim-bright, etc.) uses an NE555 Timer to generate a1-second pulse, triggered by ambient ac fields that are picked up by the human body. Read also the circuit description.

4 Bit µP's a / D Converter Decodes Keypad's Inputs: 10/13/94 EDN-Design Ideas

4 Digit Keypad

8 x 8 Audio Video Switch

Alternating On / Off Control: 

Anticipating timer switches before you push the button: 04/03/03  EDN-Design Ideas / (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

Audio Auto Shutoff:  purpose of this circuit is to automatically turn off any device plugged into its power outlets after a certain period of Time of silence

Audio Video Switch: This is an 8-input x-output audio/video switch module to be controlled from a computer, for example from the parallel port. Each audio/video output can be switched to any of the 8 inputs, separately.1-module drives1-audio/video output and has a34-pin connector to plug into the system interface. You can use video OPA-s on the4051 output instead. Note that you can get full integrated video multiplexers from Maxim.

Automatic Headlight Brightness Switch:

Automatic Switch Handles RS-232 Or RS-485 Serial Data : 09/20/04  Electronic Design - Design Briefs / The need arose for a programmable control system that handles 8-bit data to have both RS-232 and RS-485 modes. This requirement was satisfied with a serial communication controller-transceiver, an octal buffer, and a two-line port (Rx and Tx for...

Bipolar Transistor Boosts Switcher's Current By 12 times: 05/24/01 EDN-Design Ideas / PDF contains multiple circuits - scroll to find this circuit.

Build a zero-power switch supervisor: 04/05/99 Electronic Design - Ideas for Design / A recent project requirement specified the need for a special indicator to show whether a security switch was used during the time the system was powered off. Because our system has a real-time.

Bypass Switch Speeds Up Data Through Daisy Or JTAG Chain: 02/16/04 Electronic Design - Design Briefs / A daisy chain consisting of multiple devices can be quite cumbersome to control, especially when the only device that needs updating is the last one in the chain. Each device in the chain must be written to, resulting in a slow update rate. It's. . .

Capacitance Proximity Alarm

Capacitive Sensor: Special design for shop-windows animation Useful for many types of touch controls

Cell-Phone-Controlled Audio/Video Mute Switch:

Cheap Pushbutton Replaces Rotary Switch: 10/26/00 EDN-Design Ideas / PDF contains multiple circuits - scroll to find this circuit

Check Digital Or Linear Circuits With The Flick Of Switch: 03/03/03 Electronic Design - Ideas for Design / A simple logic probe in concert with a signal source can be used to check digital as well as linear circuits. With the flick of a switch, the probe can inject a test signal or check the logic state of a digital signal. Comprising just one CMOS IC...

Circuit efficiently switches bipolar LED: 11/22/2001 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 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... .

Clap Switch

Cold Activated Switch

Combinational Conjuring Trick:

Controlling a Light With Two Switches: a light or lights can be controlled by more than1-switch

Couch DropMomentary On / Off Floor Switch for Microphones:  data sheet with circuit diagram in PDF format, includes no-pop mute function

Dark Activated Switch or Porch Light Switch:

Dark-activated LED or Lamp Flasher: Simple photo-sensitive circuit - 3V battery supply

DC Motor Reversing Circuit

DC Push Button Motor Control Circuit

Debouncing Networks Make Reliable Selector: 06/05/97 EDN-Design Ideas

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.

Digital Combination Lock

Digital Switching System:

Doorbell With Counter

Electronic Keypad:

Electronic Night Light

Four Digit Keypad

Fridge Door Alarm

Frost Alarm

Garden Light Switch

Infra / Radio Remote Control Transmitter / Receiver: 

Infra/radio Remote Control Transmitter/receiver With PIC: 

Infrared Transmitter and Receiver Schematic Diagrams: 

Inline equations offer hysteresis switch in PSpice: 08/16/2001 EDN - Design Ideas / Smooth-transition switches are convenient devices in many Spice-based simulators. Their action can greatly ease the convergence process. Unfortunately, these devices lack inherent hysteresis, a helpful feature used to build UVLO (undervoltage-lockout) systems, oscillators, and other systems. Intusoft's

IR Remote Switch:

Keyboard scanner provides system supervision: 01/26/98 Electronic Design - Ideas for Design /  The circuit shown scans a numeric keypad while also generating 16-ms timing interrupts, low-line resets, and power-fail warnings for a larger system (see the figure). The core of the circuit is a versatile. . .

Keypad Encoder Commands Tape Transport: 09/02/96 EDN-Design Ideas

LAN Switch Eliminates Redundant PHY Chip: 03/31/03 Electronic Design - Design Briefs /  Advances in notebook technology create a thirst for new features and increased functionality, culminating in greater cost and shrinking space. One solution to the cost/space issues is to use a wide-bandwidth analog local-area network (LAN)

LAN/WAN Ethernet Over current And Overvoltage Protection: 05/01/00 Electronic Design - Ideas for Design /  Local-area networks (LANs) are short-distance data communication links typically within a single building or single campus environment. A LAN doesn't use common carrier circuits (i.e., the public switched telephone net work, or PSTN). By contrast a. . .

Laser Transmitter Schematics: 

Light / Dark Detector:

Light Controlled Switch #2: output a control signal suitable for relay depending on the light level

Light Operated Switch: Originally published in Everyday Practical Electronics, December1995

Lighting Third Brake Light: 

Lightning Activated Camera Shutter Trigger:

Load Sensing Automatic Switch

Logic offers complementary switch control: 12/06/2001 EDN - Design Ideas / The complementary-switch controller in Figure 1 uses a few inverter gates to provide drive signals for the complementary switches. Complementary-switch configurations find widespread use in synchronous-rectification circuits, charge pumps, full-bridge control circuits, and other circuits. The circuit in Figure 1 provides not only a complementary drive signal but also a deadtime delay ... .

Low power keypad consumes only 100 nA: 01/24/2002  EDN - Design Ideas /  Often in the use of products with keypads, one or more keys become "stuck" or are being pressed. For example, a cell phone in the bottom of a purse or in a hip pocket could have one or more of its keys inadvertently pressed and held down for a considerable period. Depending on the circuit design and implementation of the keypad interface, this condition could cause excess current to flow,... .

Magnetic Proximity Switch:

Mains Power Switcher

Maximize Battery Life And Minimize Replacements: 05/13/02 Electronic Design - Ideas for Design /  Designers and consumers want to maximize battery life in portable and handheld applications—to avoid discarding batteries that contain useful life, and to minimize battery replacements. Small battery-powered devices with wall-adapter plug-ins. . .

MIDI Controlled Switches: can drive up to128 individual relays, solenoids, motors, etc. with a MIDI note-on and note-off messages

MOSFET Replaces Switch #1: 01/20/94 EDN-Design Ideas / By using a cheap, readily available MOSFET, you can use a single-pole switch to turn a bipolar power supply on and off without consuming extra power. In Fig1, the switch simply controls the MOSFET gate, which switches on the negative supply. Resistor R, which can be several megohms, is not necessary if the ±6V rails are permanently connected to a load, such as an op-amp circuit. Because the MOSFETs RDS (ON) is a fraction of an ohm, power loss is minimal, and the circuit suits moderate-consumption, battery-operated circuitry

MOSFET Replaces Switch #2: 02/03/94 EDN-Design Ideas / You can use a single-pole switch to turn a bipolar power supply on and off without consuming extra power

MOSFET switch provides efficient AC / DC conversion: 02/17/00 EDN-Design Ideas

Multiple Remote Points Control On / Off Switch: 06/22/00 EDN-Design Ideas / PDF contains multiple circuits - scroll to find the one of interest

One Pin Keypad Features Low Component Count: 05/26/03 Electronic Design - Ideas for Design / While current-shunt-monitor ICs like the INA168 can be connected to current-shunt resistors at supply voltages of up to 60 V, the circuit shown in the figure allows current sensing at even higher voltages....

Pine Racecar Victory Judge

Ping-Pong Configuration Increases System's Conversion Throughput: 10/30/00 Electronic Design - Ideas for Design /Traditionally, "ping-pong" configurations have been used with sample-and-hold circuits to increase throughput rates in data-acquisition systems. To increase throughput, this same technique can be implemented with standard analog-to-digital. . .

Pushbutton Switch Debouncer:

Quickly discharge power supply capacitors: 07/05/2001 EDN - Design Ideas / 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 unloaded electrolytic filter capacitors for hours or even days..

Radio Control Electric Switch: 

RC Receiver hosts two independent Switches: 06/05/96 EDN-Design Ideas

Remote Doorbell Indicator

RS232C Serial Port Scans Remote Keypad: 12/04/97 EDN-Design Ideas

S Video Source Selector

Security Circuit Eschews Sophistication: 05/26/94 EDN-Design Ideas

Signal Detecting Auto Power On Unit:

Simple circuit shuts off system when supply voltage is low: 05/12/97 Electronic Design - Ideas for Design / Many low-cost and portable systems, including small consumer electronic products, operate from unregulated power supplies such as batteries or external, plug-in “power bricks.” These power sources sometimes produce lower-than-nominal output. . .

Simple soft-start circuit for switching regulators: 07/21/97 Electronic Design - Ideas for Design /  In the early stages of development, one of the many issues circuit designers must evaluate is how the circuit behaves when power is first applied. Unexpected things can happen at startup.

Simple switchers made simple pre-regulators: 07/07/97 Electronic Design - Ideas for Design /  Linear regulators are used extensively because of their simplicity, low cost, quiet operation, and clean outputs. In applications where the output voltage must be adjusted over a wide range, however, they can dissipate considerable power and require. . .

Sleeping Aid : Based on electromagnetic-field radiation Place it under the pillow-Built-in Timer

Smart Foot Switch:

Soft On / Off Switch

Solid State Relay Saves Battery's Life: 09/01/94 EDN-Design Ideas

Solid State Switch for DC Operated Gadgets

Sound Operated Switch:

Stop / Start Circuit using a Relay & Pushbutton Switches: for use when you want to manually restart a device after a power failure.

Switch Circuits: collection of Switch Circuits for temperature, light level and button controlled switching

Switch debouncer uses only one gate: 05/30/2002  EDN - Design Ideas / 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 on Delay Circuit

Switch-Debouncer IC Creates A Long-Period Timer: 10/01/01 Electronic Design - Ideas for Design /  One major application for long-period timers is in remote weather-data stations. These stations measure environmental conditions at regular time intervals and transmit the results to a central collecting facility. Since these small weather stations.

Thermal switches provide circuit disconnect : 09/04/03  EDN-Design Ideas / A single temperature sensor can provide an interrupt to a microcontroller when the measured temperature goes out of range. You need multiple temperature sensors when you have to monitor more than one hot spot. A microcontroller implements the proper protective action when one of the temperature monitors detects an overtemperature condition....

Three parts provide tenfold increase in switcher current: 08/22/2002  EDN - Design Ideas /    Industrial-control circuits often derive their power from widely varying sources that can exceed the 40V maximum rating of popular switching ICs. This Design Idea presents a simple, flexible, and inexpensive buck switcher that converts an input voltage as high as 60V to 5V at several amps. The circuit is unique in that it boosts current with almost no compromise in performance, size, or cost..

Three Way Touch Lamp:  A three-way switch to control a lamp (off-dim-bright, etc.) uses an NE555 Timer to generate a1-second pulse, triggered by ambient ac fields that are picked up by the human body. Read also the circuit description.

Time Switch

Time Switch:

Toggle Switch Debounced Pushbutton

Touch Activated Alarm: 

Touch Dimmer

Touch Switch #2

Touch Switch #3:  This is achieved using a jugfet, it is a very simple circuit and very effective to with a minimum component count working via a 1.5v cell.

Touch Switch #4:

Touch Switch using Transistors: 

Touch Switches

Triac Light Controller

Two buttons provide safe start: 07/06/00 EDN-Design Ideas / Provides a safety interlock that checks the actuation of two pushbuttons before enabling a relay. When you push both buttons, the circuit actuates the relay. At that point, you can release one of the switches without the relays switching off. The circuit was intended to lock out the engine of an underwater propulsion unit.

Use a tiny microcontroller with a large keypad: 09/02/97 Electronic Design - Ideas for Design /  Like a student needing just one more night to prepare for a coming exam, a microcontroller designer often wishes for just one more I/O line as a project approaches its final stages. Even for the relatively capable 8X752 microcontroller at 28 pins,. . .

Video monitor adapter enhances oscilloscope: 08/18/97 Electronic Design - Ideas for Design /  Video signals can be difficult to display on an oscilloscope. Normal trigger circuits in most oscilloscopes have trouble getting a stable trigger from the combined vertical and horizontal sync signals, color burst, and picture signal in a composite. . .

Video Routers: VISW 8 x4 Stereo audio/video router

Video Stabiliser :

Video Switch: This article (published in Circuit Cellar Magazine) describes a circuit which switches RGB signals between two genlocked cameras. This project used analogue switched and programmable logic (programmed using VHDL). This article is also available in PDF format and in zipped packet from Circuit Cellar Apr1999.

VISW 8 x 4 Stereo Audio / Video Router :

VOICE CONTROLLED SWITCH:  This is a slightly more harder circuit than some of the others with a higher component count but still very interesting.

Voice Over Circuit: switches automatically from sound source to microph1-when enough sound comes in from microph1-

Voltage Comparator Switch:

Water Activated Relay

Whistle On Whistle Off:  This CMOS toggle flip flop circuit has an addition of two bandpass filters and condenser microph1-so the relay can be toggled by whistling at it.

Whistle Responder: Beeps when hears your whistle A gadget suitable for key-holders, games etc.

Whistle Switch:

X Y Keypad uses µC's Serial Port: 10/10/96 EDN-Design Ideas


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