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Power Supplies: AC to DC Converters / Linear
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Power Supplies -- Main Page


Last Updated: November 30, 2017 02:27 PM

Circuits Designed by Dave Johnson, P.E. :

Tester 4-20ma Current Loop - This circuit injects an adjustable current through a wire loop.  Using a digital current meter, the current can be adjusted from near zero to over 24 milliamps . . . Hobby Circuit designed by David Johnson P.E.-May, 2012

Touch Switch 240VAC - This is another capacitance based touch on/touch off switch, which can control power to a 200 watt 240vac load . . . Hobby Circuit designed by David Johnson P.E.-July, 2006

Very Loud Pulsating Beeper - Many battery powered alarms draw excessive current when operating.  Some of the most attention-getting noise makers, such as the unit shown below, use piezo sound generators with a frequency sweeping tone.  When operating with a 9v battery, these units can often draw 100ma or more.  In many applications, a continuous alarm sound is not needed. . . Circuit by David Johnson P.E.-October, 2010

Voltage Boost to Series Regulator provided by Capacitor - 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 . . . Hobby Circuit designed by David A. Johnson P.E.-January, 1998

White LEDs powered by 24V - 24vac is a popular voltage.  It is often used in low voltage lighting systems and industrial controls.  It is much less dangerous than 120vac/240vac line voltages.  The circuit below is one method to efficiently power a cluster of 7 white LEDs from 24vac. . . Circuit by David Johnson P.E.-December, 2009

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

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:

Tacho generator rectifier-  This page is a bit different from most in that it covers the use of tacho generators as feedback elements in motor control systems.  It also covers a 'Tacho Feedback Board' extra for our Pro-120 and other controllers.  It also includes the circuit diagram.  It thus should be of interest not only to potential customers but also to electronic engineers. __ Designed by Richard Torrens

Temperature Controlled NiCad Charger-  This circuit is for a temperature controlled constant current battery charger.  It works with NICD, NiMH
, and other rechargeable cells.  The circuit works on the principle that most rechargeable batteries show an increase in temperature when the cells becomes fully charged.  Overcharging is one of the main causes of short cell life, hot cells pop their internal seals and vent out electrolyte.  As cells dry out, they lose capacity.  This circuit can quickly charge a rechargeable battery pack without any negative effects.  This circuit uses a 22VDC power supply, my version 2 circuit will run from a 12VDC supply such as a solar-powered or automobile power system. __ Designed by G. Forrest Cook

Ten-Amp 13.8 Volt Power Supply-  Sometimes amateurs like to home-brew their power supplies instead of purchasing one off the shelf at any of the major ham radio retail dealers.  The advantage to rolling your own power supply is that it teaches us how they work and makes it easier to troubleshoot and repair other power supply units in the shack.  It should be noted that there is no real cost advantage to building your own power supply unless you can get a large power transformer and heat sink for a super low price.  Of course rolling our own gives us the ability to customize the circuit and make it even more reliable than commercial units. __ Designed by N1HFX

Tester 4-20ma Current Loop-  This circuit injects an adjustable current through a wire loop.  Using a digital current meter, the current can be adjusted from near zero to over 24 milliamps . . . Hobby Circuit designed by David Johnson P.E.-May, 2012

Three Phase Bridge Rectifier-  Find out about three phase bridge rectifiers. __ Designed by REUK-Renewable Energy UK website

Touch Switch 240VAC-  This is another capacitance based touch on/touch off switch, which can control power to a 200 watt 240vac load . . . Hobby Circuit designed by David Johnson P.E.-July, 2006

Transformerless Mains Power Supply-  This power supply does not really excel in power efficiency, but it is the cheapest and most compact solution for a small power supply.  Note that the low voltage output is directly connected to the mains; it cannot be used when the low voltage part can be touched.  With the component values of the schematic, the circuit can supply12V /15mA max__

Transformerless Power Supply-  I have received a few emails asking for a transformerless power supply.  Here is such a supply.  This supply uses no heavy step down transformer and has an extremely low parts count.  The circuit can be built very small and can supply small currents for small projects.  The major downfall of this supply is that it is not isolated from the AC line and can only supply small currents __ Designed by Aaron Cake

Transformerless Power Supply-  Power Supply Circuits:  This circuit will supply up to about 20mA at 12 volts.  It uses capacitive reactance instead of resistance - so it doesn't generate very much heat.  The circuit was designed to provide a cheap, compact power supply for CMOS logic circuits that require only a few milliamps.  The logic circuits were then used to control mains equipment, using an optically-isolated TRIAC. __ Designed by Ron J.

Transformerless Power Supply (jose pino)-  Simple, low cost and easy to build power supply.  Ideal for applications that doesn’t require too much power. ( 5/28/2006) __ Designed by Jose Pino

Transient Protection of Darlington gain block Amplifiers-  AN-60034  Application Note__ MiniCircuits.com

TTL Power Supply with ‘Crowbar’ protection-  The regulator IC is the familiar fixed voltage type such as LM7805.  The 7805 is a three-pin regulator which requires a minimum voltage input of 7.5V to sustain stabilization, which an absolute maximum input voltage of 35V.  The maximum load current is 1A and the regulation against input changes is typically 3-7mV for a variation of input between 7.1V and 25V.  The regulation against load changes is of the order of 10mV for a change between 5mV and 1.5A load current.  The noise voltage in the band from 10Hz to 100KHz is 40-50uV, and the ripple rejection is around 70db.  Maximum junction temperature is 215 degrees C, and the thermal resistance from junction to case is 5 degrees C/W.  This stabilizer is used extensively for power supplies in digital equipments. __ Contact Ravi Sumithraarachchi

Two Op Amps Provide Averaged Absolute Value-  10/30/03  EDN Design Ideas:  The circuit in Figure 1 is useful when you need amplitude demodulation or an averaged absolute-value conversion.  The circuit comprises two stages, the first of which, IC1A, is a differential-output absolute-value converter.  The sec __ Circuit Design by Dobromir Dobrev, Jet Electronics, Sofia, Bulgaria

UA7812 and other UA78 Series examples-  Ham Radio - Power Supplies __ Designed by Guy Roels ON6MU

Ultra Low Drop Linear Regulator-  The circuit is a MOSFET based linear voltage regulator with a voltage drop of as low as 60 mV at 1 ampere.  Drop of a fewer millivolts is possible with better...__ Electronics Projects for You

Ultra-Linear 32W Amplifiers 500-1000MHz LZY-2-  AN-60-005 App Note__ MiniCircuits.com

Ultra-Linear 50W Amplifiers 20-512MHz LZY-1-  AN-60-004 App Note__ MiniCircuits.com

Universal AC or DC Amplifier with Opa452/Opa453 & Transistors-  Introduction During the experiments with loudspeakers, systems with loudspeakers, transformers, public announcement systems, audio distribution lines and amplifies, etc, we are in need of audio amplifier capable of providing more than 60Vpp...__ Electronics Projects for You

Unregulated Power Supply-  A basic full wave rectified power supply is shown below.  The transformer is chosen according to the desired load.  For example, if the load requires 12V at 1amp current, then a 12V, 1 amp rated transformer would do.  However, when designing power supplies or most electronic circuits, __ Designed by Andy Collison

USB charger-  I built this USB charger for my sister to charge her iPod without having to plug it into a computer.  Apple do make their own version but 1) it costs many ££ and 2) it's fun to build your own! The actual iPod in question is a first generation iPod shuffle but this charger will work with any of the iPod's ( having USB plug) or indeed, other kinds of USB devices which are in need of charging. __ Designed by Hans Summers

Use a Three-Phase Rectifier & Voltage Reducer for Offline Single-Phase Supplies-  EDN-Design Ideas -- 04/06/12  Missing diodes create gaps to allow voltage reduction. __ Circuit Design by JB Castro-Miguens, Cesinel, Madrid, Spain; C Castro-Miguens, University of Vigo, Spain; M Pérez Suárez, University of Vigo, Spain; and A Abal Pena, Tekplus, Vigo, Spain

Uses & Advantages of MERA Dual Matched MMIC Amplifiers-  AN-60032 Application Note__ MiniCircuits.com

Using Pass Transistors Beef Up Voltage Regulator current output-  Last month we learned how to make any fixed voltage regulator adjustable.  However, many fixed regulators such as the 7805 limit their output current to 1.5 amps.  While this may be adequate for many QRP transceivers, amateurs would often like to run a low power mobile 2 meter transceiver on their home-brew power supply.  All that needs to be done is to add a couple of inexpensive pass transistors as in Figure 1.__

Using the Catalog Specifications to Determine MMIC Reliability-  AN-60-030 Application Note__ MiniCircuits.com

Variable DC Power Supply 0,7-24V 50mA-2A-  Variable DC Power Supply is one of the most useful tools on the electronics hobbyist's workbench.  This circuit is not an absolute novelty, but it's simple, reliable, "rugged" and short-proof, featuring variable voltage up to 24V and variable current limiting up to 2A.  It's well suited to supply the circuits shown in this website.  You can adapt it to your own requirements as explained in the notes below __ Contact IQ Technologies

Variable Power Supply with adjustable current limiting-  A Variable power supply with adjustable current limiting - new design! 0-14V output up to 5A current. __ Designed by Steven Weber, KD1JV

Very Basic 12 volt Inverter-  This circuit will provide a fairly stable "Square Wave" Output Voltage.  Frequency of operation is Mainly determined by the 220 uF Feedback Caps.  Currently about 60 Hz.  Various "off the shelf" transformers can be used. __ Designed by G.L. Chemelec

Very Loud Pulsating Beeper-  Many battery powered alarms draw excessive current when operating.  Some of the most attention-getting noise makers, such as the unit shown below, use piezo sound generators with a frequency sweeping tone.  When operating with a 9v battery, these units can often draw 100ma or more.  In many applications, a continuous alarm sound is not needed. . . Circuit by David Johnson P.E.-October, 2010

Very Low Dropout VLDO Linear Regulators Supply Low Voltage Outputs-  DN292 Design Notes__ Linear Technology/Analog Devices

Voltage & current regulated power supply-  A Versatile and Most useful device, Especially for the Beginner __ Designed by G.L. Chemelec

Voltage Boost to Series Regulator provided by Capacitor-  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 . . . Hobby Circuit designed by David A. Johnson P.E.-January, 1998

Voltage doubler using a 555 timer-  This circuit rougly doubles the voltage of the input, however the current output is low.  doubled output is at 'V source.  ' __ Designed by Andy Wilson

Voltage Inverter II-  This simple and inexpensive circuit can produce a dual ( positive and negative) voltage from a single supply input.  It is therefore extremely useful for powering OpAmp and other circuits that require a dual voltage from a single battery.  The circuit will operate at an input voltage from around 5V to 20V and produce a output from +-2.5V to +-10V. __ Contact IQ Technologies

Voltage inverter using a 555 timer-  This circuit inverts the polarity of the input.  output is limited to less that 200mA. __ Designed by Andy Wilson

WGR1-12 Volt Wind Generator Regulator-  The WGR1 circuit is used to regulate the charging of a lead acid battery system from a DC-output wind generator.  It consumes minimal power when idle and efficiently delivers charging power to the battery when the wind generator is up to speed.  Excess charging power is diverted to a large dump load resistor, the heat produced can be used to keep the battery warm when used in cold climates.  The WGR1 circuit is designed to operate in conjunction with a photovoltaic ( solar) charge controller such as my SCC3 design. __ Designed by G. Forrest Cook

White LEDs powered by 24V-  24vac is a popular voltage.  It is often used in low voltage lighting systems and industrial controls.  It is much less dangerous than 120vac/240vac line voltages.  The circuit below is one method to efficiently power a cluster of 7 white LEDs from 24vac. . . Circuit by David Johnson P.E.-December, 2009

Windmill DIY Analog MPPT (maximum power point tracker)-  I would like to share the design of my Windmill maximum power point tracking ( MPPT) circuit in enough detail so someone with some electronics experience could make it for their windmill.  I am pleased with the performance, so far__


AC to DC Converters / Linear Power Supplies: 
#'s - A         B - K        L - S       T - Z


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