Maximizing the Life Span of Your Relays (5988-6917EN):  Aligent Application Note  (added 2/06)

Modular Relay System:  (Electronic Schematic / circuit added 4/02)

Multiple Relay Drive:  Circuit Ideas for Designers - Application Notes - Advanced Linear Devices, Inc.  (Circuit / schematic design added 6/06)

Parallel port relay interface:  (Electronic circuit added 4/05)

PC Securely Controls Relay:  11/23/95 EDN-Design Ideas / (Circuit / schematic design added 6/06) 

Photo Electric Street Light:  (added 10/05)

Pi Newood Derby Finish Line Lights:  (added 10/05)

Pi Newood Derby Finish Line using a Computer: Scores times and places.:  (added 10/05)

Power on Time Delay Relay Circuit:  (Circuit / schematic design added 6/06)

Power-Off Time Delay Relay Circuit:  (Electronic circuit added 4/05)

Relay Circuits use Reverse hysteresis:  05/08/97 EDN-Design Ideas / (Electronic Circuit diagram added 03/03)  

Relay driver saves substantial power :  07/02/98 EDN-Design Ideas  / (added 2/06)   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 serves a separate relay (0=off, 1=on). The latch's Select line latches data on the rising edge. Whenever the relay's status data changes, the relay's drive voltage rises to the full 12V for 140 msec to ensure that the relay pulls in. A series zener diode then reduces the relay's drive voltage by 50% to reduce dissipation. A ULN2803, an octal Darlington array with base resistors for direct logic interface, drives the relays. A useful feature is the inclusion of eight inductive-load clamping diodes, internally connected between the Outx pins and the Com pin. Com thus connects to the relay-supply rail....

Relay Toggle Circuit using a Dual 555 timer (556): This is probably the best toggle circuit.:  (added 10/05)

Relay Toggle Circuit using a MOSFET and Push Button:  (added 10/05)

Relay Toggle Circuit using a Single Transistor and Push Button:  (added 10/05)

Relays: Automatic Turn-off:  (Circuit added 9/04)

Relays: Delayed Turn-on:  (Circuit added 9/04)

Relays: Long Duration:  (Circuit added 9/04)

Relays: Long Duration--1 min to 20 hrs:  (Circuit added 9/04)

Relays: Long Duration--1 to 100 min:  (Circuit added 9/04)

Relays: Self Latching:  (Circuit added 9/04)

Relays: Sound Activated:  (Circuit added 9/04)

Relays: Transistor Boosted:  (Circuit added 9/04)

Relays-12 Sec to 90 min:  (added 2/06)

Remote Control turns Battery on and Off:  09/12/97 EDN-Design Ideas / (Electronic Circuit diagram added 03/03)  

SCR phase control yields solid state switch:  03/15/01 EDN-Design Ideas / (added 11/05) SCRs (silicon-controlled rectifiers) / PDF contains multiple circuits - scroll to find the one of interest, or thyristors, have higher current and voltage ratings, lower conduction losses, and more robustness than triacs. For these reasons, SCRs are better suited to high-power applications. This is high power dimmer circuit for115V AC.

Simple Circuit Drives Latching Relays:  02/01/96 EDN-Design Ideas / (Electronic Circuit diagram added 03/03)

Simple Solenoid Driver Reduces Power and Cost:  07/18/96 EDN-Design Ideas / (Electronic Circuit diagram added 03/03)  

Solenoid Driver Reduces Power and Cost:  07/18/96 EDN-Design Ideas / (Electronic Circuit diagram added 03/03)  

Solenoid Starter:  (Electronic Schematic / circuit added 4/02)

Solenoid trip circuit Works at Battery's end of life:  07/08/04 EDN Design Ideas  /  (added 1/05)  This Design Idea involves a low-power motion-detector circuit that operates from battery power for extended times.

Solid State Relay Saves Battery's Life:  09/01/94 EDN-Design Ideas / (added 2/05) 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.

Solidstate Remote Control Switch:  (Electronic circuit design added 02/05)

Solid-State Tesla Coil, #1:  (added 2/06)

Solid-State Tesla Coil, #2:  (added 2/06)

Square Tesla Coil:  (added 2/06)

Switch Intelligently Controls Current:  03/30/00 EDN-Design Ideas / (Electronic circuit added 5/02) - This circuit can intelligently control ac or dc current when connected in series with a load

Telephone in Use Relay Circuit:  (Circuit / schematic design added 6/06)

Telephone Ring Controlled Relay:  (Circuit / schematic design added 6/06)

Time Delay Relay #2:  (Circuit / schematic design added 6/06)

Time Delay Relay II:  (Circuit / schematic design added 6/06)

Time delay relay reduces inrush Current:  03/07/02  EDN - Design Ideas / (Electronic circuit added 10/03)    A transformer switching onto a line can sometimes cause a circuit breaker to trip or a fuse to blow. This phenomenon occurs even if the transformer presents no load, such as when the secondary is open. The problem arises because of the heavy magnetizing inrush current in the transformer. The amplitude of the current depends on the instant on the ac waveform at which the transformer become... .

Time delay relay uses proximity control:  03/15/01 EDN-Design Ideas / (added 11/05)

Time Delay Relay:  (Electronic Schematic / circuit added 4/02)

Transformer Driver Controls BiDirectional Switch:  07/17/97 EDN-Design Ideas / (Electronic Circuit diagram added 03/03)   -- You can use a transformer-driver IC to simply control a MOSFET on/off switch

Two Lead Solid State Breaker Resets itself:  03/30/95 EDN-Design Ideas / (added 03/03) - Simple dc circuit breaker can protect a power supply from the ever-present screwdriver or even isolate a satellites dual power system from a short circuit in one subsystem

Water Activated Relay:  (added 8/03)