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


Last Updated: October 24, 2017 02:55 PM
Circuits Designed by Dave Johnson, P.E. :

Small Pushbutton Controls 10 Amps AC - The circuit below uses a pair of long lasting lithium coil cell batteries to power a latching relay circuit.  With each activation of the small pushbutton, the relay is either latched closed or unlatched open.  Since coin cells canít provide the necessary peak current, a 500uF capacitor is used to store the needed energy.  The circuit standby current is kept very low by using a stack of five 100uF ceramic capacitors instead of the usual electrolytic cap. . . Circuit by Dave Johnson P.E.-January, 2012

Solid State Relay Requires Only 50ua Drive Current - This circuit demands a control current that is 100 times smaller than that needed by a typical optically isolated solid state relays.  It is ideal for battery-powered systems.  Using a combination of a high current TRIAC and a very sensitive low current SCR. . . Circuit by Dave Johnson P.E.-June, 2000

Solid State Relay that is Bidirectional - 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 . . . Hobby Circuit designed by Dave Johnson P.E.-May, 2009

Solid State Touch Activated Switch - It does not get any easier if you want a solid state switch that is activated by the touch of a finger.  Two small metal pins route voltage through the finger skin to a MOSFET switch.  The circuit is great for situations where a membrane type mechanical switch . . . Hobby Circuit designed by David A. Johnson P.E.-June, 2000

SSR Requires Ultra Low Control Current - 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 A. Johnson P.E.-June, 2000

Super Capacitor makes Low Voltage Latching Relay Driver - Using some small super capacitors, this circuit can latch and unlatch a mechanical relay with 10 amp contacts, from a small 3 volt power source.  By using a latching relay, power can be controlled to a load with a tiny battery . . . Hobby Circuit designed by David A. Johnson P.E.-August, 2006

Switches AC or DC power using a Latching Relay - The circuit below switches AC or DC power to a load using an ultra low power 3v latching relay with two coils.  The relay can handle about 10 amps of current, up to 250vac.  Each time the small pushbutton is pressed, the circuit either latches the relay . . . Hobby Circuit designed by David A. Johnson P.E.-December, 2009

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:

SCR phase control yields solid-state switch -  03/15/01 EDN Design Ideas:  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 __ Circuit Design by James Keith

SCR Tester -  This simple SCR tester can be made with only a couple components.  it will provide a visual 'go' or 'no-go' indication--it is simply a voltage source, a lamp, and a resistor through which gate current is supplied.   __ Designed by Tony van Roon  VA3AVR

Self Latching Relay -  This relay driver is Self-Latching which means that once it activates it will remain in that state until S1 is pressed and momentarily disrupts power to the latch __ Designed by Tony van Roon  VA3AVR

Semiconductor Relay for Automotive Applications -  Semiconductor relays provide the same function as electromechanical relays but have no moving parts, which increases their long-term reliability.  These relays provide an array of solutions, meeting the needs of todayís...__ Electronics Projects for You

Semiconductor Relays -  general info and many example circuits __ Designed by Tomi Engdahl

Simple Circuit drives latching relays -  02/01/96 EDN Design Ideas:  Figure 1 shows a low-parts-count circuit that can drive one- or two-coil latching relays.  Latching relays are useful in sensitive analog designs.  The 74ACT174 hex flip-flop has ample capability to drive the Aromat TQ2E series of latching relays.  Both windings for the TQ2E-L2-5V two-coil relay are on the same magnetic element, so the windings' fields add.  You __ Circuit Design by Roy McCammon, 3M Austin, TX

Simple Circuit Electronic Breaker -  This circuit uses the on-resistance of the MOSFET as the current sensor.  Reset it by removing the input power or the load.  The circuit draws no current unless tripped.   __ Designed by Andrew R. Morris

Simple Circuit Solenoid Driver Is Adaptable & Efficient -  06/04/12  EDN Design Ideas:  Use capacitive reactance to save energy while holding a solenoid in the energized position.   Solenoid loads generally exhibit large hysteresis.  Application of the rated voltage actuates these loads.  Once they are in position, however, you can use a significantly lower voltage to thereafter reliably hold them on.  A lower sustaining voltage results in less heat production and higher efficiency. __ Circuit Design by Jessica MacNeil

Simple Circuit Solenoid Driver Reduces Power & Cost -  07/18/96 EDN Design Ideas:  Solenoid  valves commonly control the flow of low-pressure gases and fluids in biological applications.  A typical valve may operate at 12V and draw 1A.  in systems using such valves, these power requirements can cause cost and space problems, even though a well-regulated supply is unnecessary __ Circuit Design by TG Barnett, Queen Mary College, London England

Simple Circuit SSR has zero-cross on/off switching -  EDN Design Ideas:  02/16/2015    This AC solid-state relay enables zero-cross switching with quite a simple design.   This Design idea is a solid state relay (SSR) which uses a TRIAC to switch AC loads at high current.  There are plenty of simple SSR circuits available, but this may be the simplest circuit that achieves turn-on and turn-off only when the AC line voltage is near zero. __ Circuit Design by Dan Meeks

Simple Relay Circuit -  The following schematic illustrates the Simple Relay Circuit Diagram.  When the switch S is closed in a relay circuit, current flows in the coil, causing a strong magnetic field around the coil.  The soft iron bar in the lamp circuit is attracted toward the right end of the electromagnet and makes contact with the conductor__ 

Simple Relay Step-Up Circuits -  Have you ever needed to power a 12-volt relay in a circuit but only had 6 or 9 volts available? This simple circuit will solve that problem.  it allows 12-volt relays to be operated from 6 or 9 volts, or 24-volt relays from 12 volts.  While most normal relays require the manufacturer-specified coil voltage to__ 

Simplify Solid-State Lighting Dimmer Design -  Solid-state lighting is rapidly becoming the most popular lighting option for a broad range of applications.  With the U.S.  government's mandate to save energy, incandescent lamps are being rendered largely obsolete, ...__ Electronics Projects for You

Sinewave Generator -  Scroll down.  The last circuit is a simpler R-C phase shift oscillator, but this is one with a difference: it is gated, i.  e.  it can be turned on by an input signal.  Earth the input and the oscillator stops, connect it to 5v and the oscillator starts.  The oscillator will always start in the same fashion, with a positive edge  __ Designed by Richard Torrens

Single transistor relay toggle -  The circuit below requires a double pole, double throw relay in conjunction with a single transistor to allow toggling the relay with a momentary push button.  One set of relay contacts is used to control the load, while the other is used to provide feedback to keep the relay activated or deactivated.  Several push buttons can be wired in parallel to allow toggling the relay from different locations.   __ Designed by Ashish Parab

Single Transistor Relay Toggle Circuit -  The circuit below requires a double pole, double throw relay in conjunction with a single transistor to allow toggling the relay with a momentary push button.  One set of relay contacts is used to control the load, while the other is used to provide feedback to keep the relay activated or deactivated.  Several push buttons can be wired in parallel to allow toggling the relay from different locations. __ Designed by Bill Bowden

Small Pushbutton Controls 10 Amps AC -  The circuit below uses a pair of long lasting lithium coil cell batteries to power a latching relay circuit.  With each activation of the small pushbutton, the relay is either latched closed or unlatched open.  Since coin cells canít provide the necessary peak current, a 500uF capacitor is used to store the needed energy.  The circuit standby current is kept very low by using a stack of five 100uF ceramic capacitors instead of the usual electrolytic cap. . . Circuit by Dave Johnson P.E.-January, 2012

Smartcard Controlled Relay -  Like in the spy movies, the door opens inserting an electronic card!  Very useful also to access private parks, enable photocopiers, activate showers and night light in sport resorts shared between clubs.  At last, a legal and useful application for the (otherwise vituperated) satellite-TV cards.   __ Designed by Projects & Ideas from Nutchip.com

Soft-Start for Power Amps -  Although the soft start circuit can be added to any sized transformer, the winding resistance of 300VA and smaller transformers is generally sufficient to prevent a massive surge current.  Use of a soft start circuit is definitely recommended for 500VA and larger transformers __ Designed by Rod Elliott  ESP

Solenoid Driver Is Adaptable & Efficient -  06/04/12  EDN Design Ideas:  Use capacitive reactance to save energy while holding a solenoid in the energized position.   Solenoid loads generally exhibit large hysteresis.  Application of the rated voltage actuates these loads.  Once they are in position, however, you can use a significantly lower voltage to thereafter reliably hold them on.  A lower sustaining voltage results in less heat production and higher efficiency. __ Circuit Design by Jessica MacNeil

Solenoid Driver Reduces Power & Cost -  07/18/96 EDN Design Ideas:  Solenoid  valves commonly control the flow of low-pressure gases and fluids in biological applications.  A typical valve may operate at 12V and draw 1A.  in systems using such valves, these power requirements can cause cost and space problems, even though a well-regulated supply is unnecessary __ Circuit Design by TG Barnett, Queen Mary College, London England

Solenoid trip works at battery's end of life -  8-Jul-04 EDN Design Ideas:  This design idea involves a low-power motion-detector circuit that operates from battery power for extended times.  Part of the design includes a solenoid-operated trip mechanism that triggers whenever it detects motion.  The drive circuit for the solenoid in the original design worked fine as long as the battery was fresh but failed as the battery got into the middle of its life, even though suf __ Circuit Design by Brad Peeters, Theta Engineering, Costa Mesa, CA

Solid State 120 VAC Lamp Chaser -  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

Solid State Auto Power-Off On Mains Failure -  A good number of circuits which turn off the power to the load on mains failure have already appeared in EFY.  This circuit is different because it consumes no power when...__ Electronics Projects for You

Solid state linear HF Amplifiers -  Not a project yet, but very theoretical thoughts about very practical amplifiers!  __ Designed by Manfred Mornhinweg

Solid State Power Controller -  The ckt is built around two 555 timer IC s. U1 and U2. U1 is wired as a variable duty cycle oscillator with a constant time period of around 0.1 second. Duty cycle can be varied from 0 to 100 per cent by R4 potentiometer. The output of U1 (pin 3) is connected to the rest input (pin 4) of U2. __ Designed by  Ravi Sumithraarachchi

Solid State Pulse Counting Receiver -  Notes on building a solid state pulse counting FM receiver.  This is not a final design.   __ Contact blehack @ yahoo dot com

Solid State Relay -  The basic function of a relay is to switch on power to a load using an electrically isolated, low-power control signal.  Hitherto, electromechanical relays have been the components of choice to...__ Electronics Projects for You

Solid State Relay -  Solid State Relays are available almost everywhere these days, however they remain very expensive.  Therefore, your efforts to build one yourself pays off.  Especially since it only needs a handful components and the circuitry is simple and straightforward __ Designed by Jan Hamer

Solid State Relay Requires Only 50ua Drive Current -  This circuit demands a control current that is 100 times smaller than that needed by a typical optically isolated solid state relays.  it is ideal for battery-powered systems.  Using a combination of a high current TRIAC and a very sensitive low current SCR. . . Circuit by Dave Johnson P.E.-June, 2000

Solid State Relay Space Heater Controller -  The space heater controller pictured above uses a 25 amp Solid State relay, a dual op-amp and a few other parts.  The circuit board was laid out on graph paper to work out locations for the holes.  The hole positions were then copied to a bread board to be used as a template for drilling the holes.  The bread board was then clamped on the top of the blank copper board as shown in the top picture and the marked holes were drilled using the bread board as a guide for the drill (no walking).  The drilled board was then sectioned into isolated islands using a dremel tool and router bit as shown __ Designed by Bill Bowden

Solid state relay switch -  Solid State Relay Switch is a simple kit which will help you control (ON / OFF) a single high power circuit from a low power drive.  __ Designed by Rajkumar Sharma

Solid State Relay that is Bidirectional -  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 . . . Hobby Circuit designed by Dave Johnson P.E.-May, 2009

Solid State Remote Control Switch -  Here is a solidstate remote control switch which uses readily available electronic components.  The control circuit comprises the transmitter and receiver sections.  The range of the transmitter is around seven metres.  The transmitter...__ Electronics Projects for You

Solid State Reversing -  This circuit uses solid state switching (transistors) to control direction of a DC motor.  You have precise control of the movement of the motor, and an indication of direction provided by LED's.   __ Designed by Andy Collison

Solid State Signal Lamp -  This solidstate signal lamp is a good alternative to revolving mechanical signaling lamps used in ambulances.  it uses ultra-bright blue LEDs for signaling.  However, you can replace blue LEDs with bright...__ Electronics Projects for You

Solid State Switch for DC-Operated Gadgets -  This solid state DC switch can be assembled using just three transistors and some passive components.  it can be used to switch on one gadget while switching off the second gadget...__ Electronics Projects for You

Solid State Touch Activated Switch -  it does not get any easier if you want a solid state switch that is activated by the touch of a finger.  Two small metal pins route voltage through the finger skin to a MOSFET switch.  The circuit is great for situations where a membrane type mechanical switch . . . Hobby Circuit designed by David A. Johnson P.E.-June, 2000

Solid State Voltage Stabiliser -  in india, we have a large power distribution system with heavy distribution losses and variations in industrial/ domestic load.  This results in voltage variations that may damage electrical/ electronic appliances like...__ Electronics Projects for You

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

 


Imagineering Ezine    Discover Solar Energy Dave Johnson & Associates Faraday Touch Switches



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