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Relay Circuits, Page 1
Relays:  #'s - N    O-Z
Last Updated on: Friday, August 29, 2008 02:33 PM

Circuits Designed by Dave Johnson, P.E. :
  • CHARGE COUPLED BI-DIRECTIONAL POWER MOSFET RELAY
    The circuit uses an inexpensive C-MOS inverter package and a few small capacitors to drive two power MOS transistors from a 12v to 15v supply. Since the coupling capacitor values used to drive the FETs are small, the leakage current from the power line into the control circuit is a tiny 4uA. Only about 1.5mA of DC is needed to turn on and off 400 watts of AC or DC power to a load.

Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:

12 Sec to 90 min Relay:  (added 2/06)

120 Volt AC Lamp Chaser using Solid State Relays:  This circuit is similar to the LED clock using12 neon indicator lamps instead of LEDs. It operates from2 high capacity ni-cad cells (2.5 volts) which keep it going for a couple weeks. High voltage (70 volts) for the neon lamps is obtained from a small switching power supply using a 74HC14 Schmitt trigger Squarewave oscillator, high voltage switching transistor, and10 mH high Q inductor. Most any small PNP transistors can be used that have a C/E voltage rating of 80 or more. (Circuit / schematic design added 6/06)

2 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

555 Timer MonoStable Circuit using Pushbutton:  (Electronic Schematic / circuit added 4/02)

741 Based Light Sensor:   CdS photocell used for light/dark controlled relay (Electronic circuit added 5/02)

8-Way Relay Interface Board for PC Parallel Printer Port:  (Circuit / schematic design added 6/06)

9 Second LED Relay Timer:  (Electronic Schematic / circuit added 4/02)

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 the on/ off periods of the other 2 555s which are used to flash two bulbs through the relay contacts. The flashing occurs at a rate of 4 flashes per second. The diodes are used to protect the 555 ICs from peaks. The relays should have an impedance greater than 50ohms i.e, they should not draw a current more than 200mA....   (added 10/05)

Analog Switch Lowers relay Power consumption:  12/20/01 EDN Design Ideas  /  (added 1/05)  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). ...

Assorted relay Control circuits:  (Electronic circuit added 4/05)

Basic Stamp I and PC Relay Controller:  (Electronic circuit added 4/05)

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

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....

 

CMOS Toggle Flip Flop using Laser Pointer:  (added 10/05)

CMOS Toggle Flip Flop using Push Button (CD4013):  This is fairly complex and not the best toggle circuit.   (added 10/05)

Control 120 Volt AC Relay with TTL:  (Electronic Schematic / circuit added 4/02)

Control 120VAC Relay with TTL:  (Circuit / schematic design added 6/06)

Controlling Relays with Logic Voltages:  (Electronic Schematic / circuit added 4/02)

Countdown timer with Relay:  (added 8/03)

Dancing LEDs:   A LED sequencer, following the rhythm of music or speech 9 Volt Battery-operated portable unit (Circuit added 9/04)

Dark/Light Activated Relay:  (Circuit / schematic design added 6/06)

Electronic Thermostat Relay Circuit:  (Electronic Schematic / circuit added 4/02)

Inexpensive Relays Form Digital Potentiometer:  03/13/98 EDN-Design Ideas / (Circuit / schematic design added 6/06)   -- Build a digitally controlable isolated potentiometer that can tolerate voltages up to 60-Volt dc

Infrared Relay with Relay Output:  (Electronic circuit added 4/05)

KD2BD Video Operated Relay :  turns on relay if there is video signal present in the input (Electronic circuit added 5/02)

Key reading circuit saves I/O pins:  02/06/03  EDN-Design Ideas / (added 8/03) Some microcontroller applications usually use too many I/O pins to read keys or onboard switches; in many cases, few pins remain available for other uses. Some alternative ways to read keys yield more free pins. First, consider some ways to effect key reading. Table 1 presents a comparison of four methods with references to circuit configurations (figures 1, 2, 3, and 4)

Light activated relay #1:  (Circuit / schematic design added 6/06)

Light Activated Relay (toggled):  (added 11/05)

Light/Dark Detector:  (Electronic Schematic / circuit added 4/02)

Load Sensing Automatic Switch:  apply power to the entire audio system by turning on1-item, simple circuit (Electronic circuit added 5/02)

Long Duration--1 min to 20 hrs Relay:  (added 2/06)

Relays:  #'s - N    O-Z



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