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Relay Circuits
#'s - K         L - R          S - Z


Last Updated: October 13, 2017 03:01 AM
Circuits Designed by Dave Johnson, P.E. :

50ua Current Drives Solid State Relay Requires Only - Most solid state relays require at least 5ma and often more input control current, to fully turn on the device.  But such current levels often force battery powered circuits to use excessively large batteries.  The relay hobby circuit shown below demands only 50uA of input current . . . Hobby Circuit designed by David Johnson P.E.-June, 2000

Bidirectional Solid State Relay - The circuit below can switch up to 4 amps of current with a peak voltage up to 20v.  It is fully isolated using two inexpensive red LEDs.  One LED forms a red light source, which illuminates a second red LED.  The circuit takes advantage of the 1.5v. . . Circuit by Dave Johnson P.E.-May, 2009

Computer Controlled Power Relay - Often there is a need to turn on and off a 120vac device using a low power +5v logic signal from a computer.  The circuit below shows how this could be done.  The circuit uses a power relay with a 120vac coil and 10 amp contacts.  A small solid state relay turns on and off the relay.  The solid state relay provides 5KV isolation from the computer . . . Hobby Circuit designed by David Johnson P.E.-July, 2011

Dusk To Dawn Latching Relay -  Over the years I have had to replace many dusk to dawn switches for outside lights.  These switches turn on a light during the night, then switch them off during daylight hours.  Some commercial switches are not sensitive enough to detect when the sun is out.  Others flutter badly during the dawn and dusk switching transitions, burning out compact fluorescent lamps, which do not like rapid power fluctuations. . . . Circuit by David Johnson P.E.-July, 2017

Finger Tap Piezo Relay - This circuit uses a flat piezo wafer, glued inside a plastic box, as a finger tap sensor.  With each tap of a finger to the box holding the wafer, the circuit turns on and off AC or DC power to an external device.  The circuit is powered by a 9v 9v battery . . . Hobby Circuit designed by David Johnson P.E.-December, 2010

High Temperature Thermocouple activates Relay - Voltage from a high temperature thermocouple activates a relay when the sensor detects a temperature above 1000 degrees F . . . Hobby Circuit designed by David A. Johnson P.E.-July, 2006

High-speed 75MHz light receiver - This circuit uses one tiny C-MOS inverter IC to form a modulated light receiver with a very fast response.  It is designed around a PIN photo diode that is packaged for use with plastic optical fibers.  It can be used as an optical fiber receiver.  By using the open end of the optical fiber it can "sniff" out any modulated light signals. . . Circuit by Dave Johnson P.E.-June, 2000

Capacitance Proximity Switch
Draws very low power - Ideal for battery-powered applications
6 Models Available - Call 806-368-7747

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

1 min to 20 hrs Relay -  This is an accurate long-duration time delay driver, switchable between 1 and 10 minutes or 10 to 100 minutes and whose function does not depend on electrolytic capacitors.  Film dielectric caps have been selected.  IC 1 is configured as a free-running astab __ Designed by Tony van Roon  VA3AVR

1 oscillator drives multiple solid-state relays -  16-Mar-06 EDN Design Ideas:  A conventional electromechanical relay often makes sense for switching large amounts of load current on and off and when proportional control of the load’s current or voltage is unnecessary __ Circuit Design by Juan Ramón Vadillo Pastor, SOR Internacional SA, Saint Quirze Del Valles, Barcelona, Spain

12 sec to 90 Minute Time Relay -  Schematic and notes only, no circuit description provided.   __ Designed by Tony van Roon  VA3AVR

120 VAC Lamp Chaser using Solid State Relays -  This circuit is basically the same as the 10 channel LED sequencer with the addition of solid state relays to control the AC lamps.  The relay shown in the diagram is a Radio Shack 3 amp unit (part no.275-310) that requires 1.2 volts DC to activate.  No current spec was given but I assume it needs just a few __ Designed by Bill Bowden

120 Volt AC Lamp Chaser using Solid State Relays -  This circuit is similar toLED 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) forneon lamps is obtained from a small __ Designed by Bill Bowden

2 Lead Solid-state Breaker Resets itself -  03/30/95 EDN Design Ideas:  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 __ Circuit Design by Phil Harvey, Technology Integration Inc, Bedford, MA

2 Simple Circuit Relay Based Motorcycle Alarms -  Motorcycle Alarm Circuits:  These are two - easy to build - relay-based alarms.  You can use them to protect your motorcycle - but they have many more applications.  if you use relays with 6-volt coils - they'll protect your "Classic Bike".  Both alarms are very small.  The completed boards occupy about half a cubic-inch - 8 cc.  The standby current is zero - so they won't drain your battery.  __ Designed by Ron J.

220V Solid State Flashing Lamp with 555 -  This 220V mains operated solid state flashing lamp circuit uses a 555 timer IC to control the ON and OFF times of a TRIAC which controls power to the load.  The power supply for the IC is obtained by half wave rectifier (D1) , a stabilizer circuit (D2 and R1) and filter capacitor C1.  The lamp stays ON for about 1 second and OFF __ Designed by Popescu Marian

4 channel infrared remote relays -  4 Channel infrared (iR) Remote is a simple kit using the famous HT12A and HT12D encoder / decoder chips from Holtek __ Designed by Rajkumar Sharma

5 channel infrared remote relays -  5 Channel infrared (iR) Remote is a simple kit using the famous HT12A and HT12D encoder / decoder chips from Holtek __ Designed by Rajkumar Sharma

50ua Current Drives Solid State Relay Requires Only -  Most solid state relays require at least 5ma and often more input control current, to fully turn on the device.  But such current levels often force battery powered circuits to use excessively large batteries.  The relay hobby circuit shown below demands only 50uA of input current . . . Hobby Circuit designed by David Johnson P.E.-June, 2000

555 (TLC555) Relay Driver -  Many integrated circuits have undocumented features or abilities.  This is one of them.  The TLC555 output (pin 3) can sink a 100mA load to 1.28V.  The open drain transistor reset (pin 7) can sink 100mA to 1V.  Tying both lines together is permissible because they are logically the same polarity and this potentially doubles the __ Designed by Jim Keith

555 Timer MonoStable using Pushbutton -  The two circuits above illustrate using the 555 timer to close a relay for a predetermined amount of time by pressing a momentary N/O push button.  The circuit on the left can be used for long time periods where the push button can be pressed and released before the end of the timing period.  For shorter periods, a capacitor can be used to isolate the switch __ Designed by Bill Bowden

60 Watt RF Amplifier -  Soild state RF power amplifier using iRF840.  Simple and easy to construct.  iRF840 can handle a maximum power output of 125 Watts.  __ 

6a, 6v Relay Solar Charge Control -  This 6V solar charge regulator meets most small-scale 6V application requirements.  With a current rating of 6A, it can handle up to a 50W solar panel.  its principle of operation is very simple and there is only one adjustment: cut-out voltage.  Many inexpensive commercial solar charges available use, I believe, this technique.  However, this particular […]__ 

741 Based Light Sensor -  The circuit as shown act as a light sensor.  Under normal conditions the resistance of the LDR is high, keeping pin 2 low.  When light falls onto the LDR the resistance drops to a couple hundred ohms and triggers pin 2 high which biases the base of Q1 via pin 6 and R4 and in turn activates the relay __ Designed by Tony van Roon  VA3AVR

8 Channel LPT relay board -  Channel Relay Board is a simple and convenient way to interface 8 relays for switching application in your project.  __ 

8 Channel Relay Board -  This project is a general purpose 8 Channel Relay Board.  Description 8 Channel Relay Board is a simple and convenient way to interface 8 relays for switching application in your project.  input voltage level support TTL as well as CMOS .  Easy interface with Microcontrollers based projects and analog circuits.  Specifications: input supply 12 VDC__ 

9 Second Digital Readout Countdown Timer -  This circuit provides a visual 9 second delay using a 7 segment digital readout LED.  When the switch is closed, the CD4010 up/down counter is preset to 9 and the 555 timer is disabled with the output held high.  When the switch is opened,  __ Designed by Bill Bowden

9 Second LED Relay Timer -  This circuit provides a visual 9 second delay using a 7 segment digital readout LED.  When the switch is closed, the CD4010 up/down counter is preset to 9 and the 555 timer is disabled with the output held high.  When the switch is opened,  __ Designed by Bill Bowden

AC Line Current Detector -  This circuit will detect AC line currents of about 250 mA or more without making any electrical connections to the line.  Current is detected by passing one of the AC lines through an inductive pickup (L1) made with a 1 inch diameter U-bolt wound with 800 turns of #30, #35 magnet wire.  The pickup could be made from other iron type rings or __ Designed by Bill Bowden

AC Power Line Power Load Sensing Automatic Switch -  WARNiNG:  This circuit requires experience with mains wiring.  Do not attempt construction unless experienced and capable.  Death or serious injury may result from incorrect wiring.   __ Designed by Rod Elliott  ESP

AC-AC-SSR Solid State Relay -  This is a AC Control input AC Output SSR Solid State Relay.  When a Process Controller has an AC output or a system generates an AC signal of above 100V AC to signal the load to turn on, this device can be used.  A BTA40-600 and MOC3041 are used in__ 

Alternating On-Off Switch, #1 -  This circuit uses three easily available 555 timer IC s.  All three work as astable multivibrators.  The first 555 has an on period and off period equal to 1 sec.  This IC controlson/ off periods ofor 2 555s which are used to flash two bulbs throughrelay contacts __ Designed by Tony van Roon  VA3AVR

Alternating On-Off Switch, #2 -  This circuit is the transistor version of the 4069 CMOS type.  Every press of the push-button will activate or de-activate the relay.  if you decide to mofify the circuit for 9V or higher, make sure the working voltage of the electrolytic capacitors are 25V instead of 16V.  The BC557B and BC337-40 are European transistors manufactured by Philips in the Netherlands.  Replacements such as the 2N3406 (PNP) , 2N3904 (NPN) , are okay, just watch the pin orientation which differs in regards to the collector/emitter __ Designed by Tony van Roon  VA3AVR

Analog switch lowers relay power consumption -  20-Dec-01 EDN Design Ideas:  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)  __ Circuit Design by Steve Caldwell, Maxim Integrated Products, Chandler, AZ

Analog switch lowers relay power consumption -  Abstract: Design idea   outlining a method to use an analog switch and discrete components to reduce the power dissipated in relay actuation -- Relays are often used as electrically controlled switches.  Unlike transistors, their switch contacts are electric__ Maxim IntegratedAPPLICATION NOTE 956

Audio Amplifier Output Relay Delay -  This is a simple circuit which I built to one of my audio amplifier projects to control  speaker output relay.  The purpose of this circuit is to control  relay which turns on  speaker output relay in  audio amplifier.  The idea of  circuit is wait around 5 seconds after  power up until  speakers are switched to  amplifiers  __ Designed by Tomi Engdahl

Automatic Turn-off Relay -  The above circuits is similar to the "delayed turn-on" type but now configured as an automtic turn-off type.   The diagram shows how the circuit function can be reversed so that the relay turns on when power is applied __ Designed by Tony van Roon  VA3AVR

Basic Stamp I & PC Relay Controller -  This project shows you how to build a relay controller using the Basic Stamp I interfaced to the PC serial port.    The Visual Basic 5 software developed for the interface lets you interact with the Basic Stamp to turn ON/OFF up to (2) relays attached to the Basic Stamp i/O pins.    As shown below in the screen capture of PC-Relay, it's easy to select the desired com port using the drop-down menu __ Designed by Reynold's Elec

Bidirectional Solid State Relay -  The circuit below can switch up to 4 amps of current with a peak voltage up to 20v.  it is fully isolated using two inexpensive red LEDs.  One LED forms a red light source, which illuminates a second red LED.  The circuit takes advantage of the 1.5v. . . Circuit by Dave Johnson P.E.-May, 2009

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Relays#'s - K         L - R          S - Z

 


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