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Silicon Controlled Rectifier (SCR) Circuits
SCRs:   #'s -A      B - K      L - Q      R - Z

 

Last Updated: October 24, 2017 02:55 PM

Circuits Designed by Dave Johnson, P.E. :

Capaciatance-Based Touch Switch -  This is another capacitance based touch on/touch off switch, which can control power to a 200 watt 240vac load . . . Hobby Circuit designed by Dave Johnson P.E.-February, 2002

Caps Provide Voltage Boost to Series Regulator -  This circuit adds some capacitors and diodes to a traditional transformer type series regulator circuit to extend the normal operating range.  it can insure regulation during low line voltage conditions or it can squeeze a few more watts out of a plug-in-the-wall power adapter power supply. . . Circuit by Dave Johnson P.E.-January, 1998

Charge Coupled MOSFET Relay #2 -  This circuit acts as an AC/DC relay with a rating up to 50 volts peak and up to 10 amps of current.  The differential oscillator supplies voltage to the gates of the two FETs with good isolation will drawing only 1.5ma of current. . . Circuit by David A. Johnson P.E.-October, 2005

Circuit Eliminates 9v Battery -  if you use 9v battery powered devices for long periods of time, you may get tired of constantly changing batteries.  The circuit below can be wired into any 9v battery powered device, drawing power from an external AC to DC power adapter.  I designed the c . . . Hobby Circuit designed by Dave Johnson P.E.-December, 2009

Circuit Protects from Battery Polarity Reversal -  This simple circuit can protect a sensitive electronic circuit from an accidental connection of a battery with a reversed polarity.  The N-channel FET connects the electronic device to the battery only when the polarity is correct.  The circuit shown was. . . Circuit by David Johnson P.E.-March, 2002

Classic Plus & Minus DC Power Supply -  This is a classic example of a regulated DC power supply that produces both a positive 15v and a negative 15v from a 20vac wall adapter. . . Circuit by David A. Johnson P.E.-October, 2005

Convert AC to DC signal with is Full Wave Rectifier -  This is a classic circuit that can accurately convert an AC signal to DC.  Using a LF412 high speed dual op amp, this circuit will rectify any signal up to about 100KHz with a minimum amplitude of about 50mv peak to peak.  At 40KHz the input signal can be . . . Hobby Circuit designed by David A. Johnson P.E.-July, 2006

Display RF Signal Strength -  Many cordless telephones, computer networks and cell phones use a RF transmitter lefted on the 2.45GHz band.  Using a microwave diode detector and 100uA meter, this passive circuit will display the strength this signal.  The drawing shows how a bent piece of wire can be used as the antenna. . . . Hobby Circuit designed by David Johnson P.E.-July, 2006

Energy Harvesting using a Current Transformer -  Energy harvesting is all the rage these days.  With some modern electronics, information from low power sensors can be sent to a distant data collection point using a low power RF transmitter.  To power these remote sensors, various energy sources can be. . . Circuit by David A. Johnson P.E.-January, 2010

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:

Capaciatance-Based Touch Switch -  This is another capacitance based touch on/touch off switch, which can control power to a 200 watt 240vac load . . . Hobby Circuit designed by Dave Johnson P.E.-February, 2002

Capacitor voltage stepper using 555 timer -  in conventional voltage multiplier circuits, AC is used to charge the capacitors network via diodes in one cycle and discharge in the other cycle in a particular combination, which thereby produces multiples of the peak voltage.  However, this circuit works on a different principle, and it is DC which is doubled.  it can be used to power low current circuits.__ 

Caps Provide Voltage Boost to Series Regulator -  This circuit adds some capacitors and diodes to a traditional transformer type series regulator circuit to extend the normal operating range.  it can insure regulation during low line voltage conditions or it can squeeze a few more watts out of a plug-in-the-wall power adapter power supply. . . Circuit by Dave Johnson P.E.-January, 1998

Car Converter - 12V to 9V -  To get a more precise output voltage, replace zener diode Z1 with 10V and R1 with a 1Kilo ohm potentiometer.  A Coolrib for Q1 is optional but highly recommended.  You can replace Q1 for a more robust type to get more output amps depending on your requirements.  Simple circuit to power your 9 volt cassette recorder and other stuff __ Designed by Tony van Roon  VA3AVR

Car Ignition Coil Driver from 110V AC -  This SCR Circuit can run a Car ignition Coil in your home, to Obtain High Voltage.   __ Designed by G.L. Chemelec

Charge Coupled MOSFET Relay #2 -  This circuit acts as an AC/DC relay with a rating up to 50 volts peak and up to 10 amps of current.  The differential oscillator supplies voltage to the gates of the two FETs with good isolation will drawing only 1.5ma of current. . . Circuit by David A. Johnson P.E.-October, 2005

Charge Monitor for 12 Volt Rechargeable Lead Acid Battery -  A battery is a vital element of any battery-backed system.  in many cases battery is more expensive than system it is backing up.  Hence we need to adopt all practical measures to conserve battery life.  As per manufacturer's data sheets, a 12V rechargeable lead-acid battery should be operated within 10.  iV and 13.8V.  When battery charges higher than 13.8V __ 

Charge-Pump Voltage Doubler with Regulator -  Schematic only __ Designed by va3iul

Charger for gel lead acid batteries -  This high-performance circuit first quickly starts (Tony van Roon's and holds) the charge at 2 amp, but as the voltage rises the current will consequently decrease.  When the current falls below 150mA, the charger automatically switches to a lower 'Float' voltage to prevent overcharging.  At the point that a full charge is reached, Q1 will bias and the LED will light.   __ Designed by Tony van Roon  VA3AVR

Circuit Eliminates 9v Battery -  if you use 9v battery powered devices for long periods of time, you may get tired of constantly changing batteries.  The circuit below can be wired into any 9v battery powered device, drawing power from an external AC to DC power adapter.  I designed the c . . . Hobby Circuit designed by Dave Johnson P.E.-December, 2009

Circuit forms constant-current SCR -  02/01/01 EDN Design Ideas:  A typical SCR (silicon-controlled rectifier) requires a trigger current, which causes the SCR structure to latch on.  Once the device latches, the current through the SCR is solely a function of external component values.  The SCR has no inherent ability to limit the current flow once it latches on.  Current continues to flow, as long as the current exceeds a minimal value known as the holding current.  The circuit in Figure 1 is similar to an SCR, because it also requires a trigger current to latch into its on state.    __ Circuit Design by Robert Buono, Ringwood, NJ

Circuit Offers Improved Active Rectification -  02/06/03 EDN Design Ideas:  Build an adjustable high-frequency notch filter - Rectifiers convert ac signals to dc.  You can combine a diode and a load resistor to create a half-wave rectifier, provided that the amplitude of the ac source is much larger than the forward drop of the diode (typically 0.6V].  Unfortunately, you can't use this method to rectify signals that are smaller than a diode drop __ Circuit Design by Reza Moghimi, Analog Devices Inc, San Jose, CA

Circuit Protects from Battery Polarity Reversal -  This simple circuit can protect a sensitive electronic circuit from an accidental connection of a battery with a reversed polarity.  The N-channel FET connects the electronic device to the battery only when the polarity is correct.  The circuit shown was. . . Circuit by David Johnson P.E.-March, 2002

Classic Plus & Minus DC Power Supply -  This is a classic example of a regulated DC power supply that produces both a positive 15v and a negative 15v from a 20vac wall adapter. . . Circuit by David A. Johnson P.E.-October, 2005

CMOS hex inverter generates low-distortion sine waves -  06/09/05  EDN Design Ideas:  Audio signal source uses hex inverter and handful of passives __ Circuit Design by Al Dutcher, West Deptford, NJ

CMOS inverters convert RF to digital signal -  01/05/06 EDN Design Ideas:  Hex-inverter-based design suits frequencies up to180 MHz __ Circuit Design by Francis Rodes

Compressor-Mate -  protection for refrigerators, freezers and air conditioners  __ Designed by Tony van Roon  VA3AVR

Considerations for Successive Approximation A ->D Converters -  Linear Technology AN17 __ Designed by Jim Williams - Dec 1st, 1985

Convert AC to DC signal with is Full Wave Rectifier -  This is a classic circuit that can accurately convert an AC signal to DC.  Using a LF412 high speed dual op amp, this circuit will rectify any signal up to about 100KHz with a minimum amplitude of about 50mv peak to peak.  At 40KHz the input signal can be . . . Hobby Circuit designed by David A. Johnson P.E.-July, 2006

Converting a PCS Power Amplifier to 13cm Ham Radio Band -  Schematic only, no circuit description __ Designed by 2001 - YO5OFH, Csaba Gajdos

Crow Bar #1 -  Depending on the setting or R1, when the voltage exceeds a certain amount, SCR1 triggers, which activates relay RY1 and opens the circuit.  S1 resets the SCR by interrupting power to it.  This is a simple crow-bar circuit for low amperage protection, up to 4 amps at 30V max.  Adjust the SCR for a model that suits your needs.   __ Designed by Tony van Roon  VA3AVR

Crow Bar #2 -  This circuit can be added to any power supply design that does not have additional circuit protection.  When the voltage exceeds either 10V or 30V, depending on the voltage switch setting via the front panel, the zener diode ZD1 conducts and fires the gate of the SCR.  This provides a short-circuit over the output voltage and in turn will blow the AC input fuse of the powersupply you wish to protect __ Designed by Tony van Roon  VA3AVR

Current booster for 78nn series voltage regulators -  Volt regulators such as the LM708, and LM317 series (and others) sometimes need to provide a little bit more current then they actually can handle.  if that is the case, this little circuit can help out.  A power transistor such as the 2N3772 or similar can be used (See the project on the 3-part variable power supply) __ Tony van Roon  VA3AVR

DC Power Supply -  Build a simple DC supply having three output terminals: regulated +5VDC, unregulated +10VDC and 7.5VAC.  The supply is suitable for microcontroller experimenting.   __ Designed by Wichit Sirichote

DC to AC inverter using a 555 timer -  This DC-to-AC inverter schematic produces an AC output at line frequency and voltage.  The 555 is configured as a low-frequency oscillator, tunable over the frequency range of 50 to 60 Hz by Frequency potentiometer R4.  The 555 feeds its output (amplified by Q1 and Q2) to the input of transformer T1, a reverse-connected filament__ Tony van Roon  VA3AVR

Desktop Power Supply from a PC -  if you find building your own desktop powersupply from a recycled PSU and a few parts from the local electronics store appealing, then grab some tools, pour yourself a cup of coffee (or personal preference) and let's get started. The LED (light emitting diode) was also salvaged from an old PC. if you want to add a power on indicator,  __ Designed by Andy Batts

Digital Bench Power Supply -  PIC  Project  This unit delivers 0 to 20 volts at up to 4 amps in 0.1volt increments.  The entire device runs on a PIC 16F870 (about $3 in small quantities).  This is basically a switching power supply with the voltage regulation done in software.  The PIC  used here has analog inputs (used to measure voltage and current) and hardware PWM (pulse width modulation) output used to control the power.   __ Designed by Luhan Monat-Mesa Arizona

Display RF Signal Strength -  Many cordless telephones, computer networks and cell phones use a RF transmitter lefted on the 2.45GHz band.  Using a microwave diode detector and 100uA meter, this passive circuit will display the strength this signal.  The drawing shows how a bent piece of wire can be used as the antenna. . . . Hobby Circuit designed by David Johnson P.E.-July, 2006

Dry cell battery charger -  The circuit of dry cell charger is very simple utilizing very few components.  The working of this circuit is based on PCR (Periodic Current Reversal) principle.  Where low AC voltage is given to dry cell for charging.  A 6V-0V/1 amp secondary transformer is used for step down of AC voltage.  The time for charging is 12 to 16 hour.__ 

Dual 12V Power Supply -  Schematic only __ Designed by Tony van Roon  VA3AVR

Dual Polarity Power Supply -  This dual polarity power supply is easy to build, requires few parts, and is adjustable from 0-15 volts.  it is great for powering op amp circuits, as well as other circuits that require a dual supply voltage. 
 __ Contact IQ Technologies

Dual Voltage Power Supply -  The following circuit Diagram of (DUAL VOLTAGE POWER SUPPLY) can be used for Misc..  application.   it requires a few components to built.  The most important components of this circuit are REGULATORS.1 : (AN) 7812 and 2 : (AN) 7912 AN7812 is the Positive Voltage Regulator.  it regulates the voltage from (almost) 24vDC to 12vDC (accurate). __ Contact IZHAR FAREED

Dynamo Current & Voltage Regulator -  Useful for lovers of older cars, motorcycles and boats. __ Designed by Manfred Mornhinweg

Efficient LED Power Supply Has Battery Backup -  04/08/10 EDN Design Ideas:  Power three to six LEDs from an ac- or dc-power source and charge a backup battery.   __ Circuit Design by Zhihong Yu, Juno Lighting Group, Des Plaines, IL

Emergency Power -  This unit was constructed in a plastic 4-outlet juction box ($5 from Home Depot).  The front panel is cut from 60-thou Lexan, and a scrapped Pep-Boys battery charger provided the transformer.  The PIC 16F870 keeps track of battery voltage as well as both charging and discharging currents.   __ Designed by Luhan Monat-Mesa Arizona

Energy Harvesting using a Current Transformer -  Energy harvesting is all the rage these days.  With some modern electronics, information from low power sensors can be sent to a distant data collection point using a low power RF transmitter.  To power these remote sensors, various energy sources can be. . . Circuit by David A. Johnson P.E.-January, 2010

EPR-32: 25 Watt Multiple Output TOP245P Supply -  This design kit is an AC-DC power supply with universal input and 4 outputs.  The design, rated for 20 W (25 W peak) , is implemented using a TOP245P device from the TOPSwitch-GX IC family and an EEL25 core in a flyback topology.  __ 

Expanded Scale Battery Volt Meter -  This circuit is used to measure the voltage on a 12V (nominal) lead acid rechargeable battery system.  it was specifically designed for use in solar powered systems, but is general enough that it can be used for automotive or other 12V systems.  Lead acid batteries normally spend their working lifetime in the voltage range of 11-15 Volts.  This meter circuit __ Designed by G. Forrest Cook

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SCRs:   #'s -A      B - K      L - Q      R - Z

 


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



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