Homo ludens electronicus

My interest in electronics started when I was 12 years old, although I had built electric devices (lighting systems, flashlights, solenoids, even a motor) much earlier. At age 12 I started the real thing: Radios, sound effect generators, light games, etc. This obsession of building things led to a career in electronics, but also it has become my most interesting hobby. I regularly design and build things, and now I will share my better documented projects with you. Each of the following links leads to a page giving constructional information (schematics, sometimes printed circuit layouts, and text) for an electronic project. You are welcome to use this information for educational purposes and for your own use, but please be honest enough not to make business with them. Any kind of commercial use must first be authorized.

Power supply and switching technology

13.8 Volt, 20 Ampere linear power supply: A semi-traditional power supply for communication equipment, using negative-rail regulation with grounded pass transistors in a configuration that gives some unique advantages.

13.8 Volt, 40 Ampere switching power supply: A heavy duty, highly efficient, small and lightweight power supply specially designed for use with communication equipment. This article was originally published in the QST magazine. Includes text, schematic diagram, printed circuit board layout, and some photos.

160 Volt, 3 Ampere DC motor power supply: A very compact, efficient and simple off-line buck regulator.

DC-DC converters : Two converters are shown here. One powers a VCR or similar device from a car battery, while the other powers a model airplane glow plug from 12V.

12V input 12V battery charger : Well suited for charging gelled batteries from a car, with the engine running or stopped.

12 Volt fluorescent lamp drivers: Three schematics of 12 V drivers for 2, 8 and 20 Watt, plus a lot of explanations about fluorescent tubes. Use the drivers for camping, emergency, boating, etc.

Single-cell LED flashlight: A driver circuit for high efficiency white LEDs that runs on a single rechargeable or alkaline cell. 

Improved single-cell LED flashlight: This one uses a single half-watt LED, and SMDs on a small PCB.

High power LED flashlight: Using a Cree LED, homemade lens, rechargeable batteries, two regulated power levels, and electronic switching.

Solar panel regulator: A simple but good linear shunt voltage regulator for solar panels, that includes deep-discharge protection. This design is for 12V systems with panels delivering up to 7A, but it can be easily scaled for other sizes. I have built several of these regulators.

Another solar panel regulator: This is a switching shunt regulator which is very simple and reliable, but does not regulate as smoothly as the one above and has no deep-discharge protection. It was built for a yacht.

Dynamo current and voltage regulator : Useful for lovers of older cars, motorcycles and boats.

Voltage regulator for synchronous generator: Also called an AVR.

Voltage regulator for brushless synchronous generator with harmonic excitation winding: Particularly suited for TFDW and similar generators.

Electronic Load Controller for microhydro system: A key component of small water turbine installations.

Spot welder using microwave oven transformer: Simple, cheap and effective!

T12 Soldering Iron Temperature Controller: Maybe the cheapest way to get yourself a temperature-regulated  soldering iron!


Small audio amplifiers: Making small, inexpensive, simple 1-Watt audio amplifiers that produce high quality sound.

12 Volt powered, 4x15 Watt audio amplifier : Using car audio chips and intended for installation inside a computer.

Awfully Antique Audio Amplifier : A funny retro project, and a new standard for schematic symbols!

Active HiFi speakers: A pair of large three-way speakers with built-in active cross-over and expanded class-A amplifiers, exhibiting very high sound quality, while being neither hard to build, nor expensive. Schematic diagram, printed circuit board layout, and several photos are included.

Version #2 of my active HiFi  speakers: Featuring new electronics, some new drivers, and lots of musings about audio technology.

Amateur Radio

40 meter SSB QRP transceiver: In 1987 I built this radio. It has been published in a national ham radio magazine, and now finally found its way into the web!

SWR meter for 1 to 1300 MHz: A very simple design, cheap to built, does not require adjustment and works well! Depending on specific components and construction technique used, the upper frequency limit will be somewhere between 150MHz and 5GHz!

An automatically tuned HF mobile antenna:  This elegant design covers the complete spectrum from 7 to 30 MHz at less than 1.3:1 SWR, is compact, very weatherproof, robust and has good performance. This article was first published in the QEX / Communication Quarterly magazine. The article comes in five pages, with lots of photos, mechanical drawings, schematic diagram, PCB layout and software listing. Exact duplication is not for the faint of heart, but some of you may find individual parts and ideas useful for your own projects!

144MHz to 50MHz receive converter: A simple accessory for a satellite station, that allows using a 6 meter capable radio in conjunction with a typical S-band to 2 meter converter.

FodTrack : My world-famous realtime satellite tracking system!

A homemade replacement for the Yaesu FTS-8 subtone encoder: Using just a PIC and an active filter!

High efficiency, legal limit, solid state linear HF amplifiers: Not a project yet, but very theoretical thoughts about very practical amplifiers!

Digimodes improvement for the TS-450/690: Fix that nasty distortion on the packet connector audio output!

Voice identifier for a repeater station: Designed as a drop-in replacement for the VHF Engineering repeater's CWID, it can be used in other equipment too.

Building an SDR around a Red Pitaya: Description of a project in progress. A software-based HF transceiver with high power EER final stage.

A 50W LDMOSFET HF linear amplifier for the Red Pitaya: Quick and inexpensive way to put the Red Pitaya on the air.

More radio!

15-band world receiver: A modern classic! Combines antique and current technologies.

Small AM transmitter: A quick and dirty 1MHz transmitter to send old music into old radios!

80 Watt FM stereo transmitter: A high quality broadcast transmitter big enough for a medium town!

Designing and building Conical Horn Antennas: These are easy to build and are a good choice for LTE, extended range WiFi and other uses.

Measuring equipment of all sorts

Equivalent Series Resistance meter: Use this handy device to find all those degraded electrolytic capacitors!

Power inductor tester: Measures inductance, saturation current, shows inductor linearity, etc. Usable with SMPS transformers, inductors, audio components, and some RF and line frequency ones.

Ferrite core loss meter: A simple gadget to measure the loss of ferrite cores used in switching power supplies, under real operating conditions.

Portable oscilloscope: When I was a poor student, many years ago, I built my own 12V-powered oscilloscope! 

Hygrometer and hygrostat: A simple handheld relative humidity meter, complete with settable control output.

Altimeter/Variometer for free  flying: A handheld instrument intended for the paraglider and hang glider pilot. Displays altitude above sea level, altitude above take off, climb and fall rates, flight time, maximum altitude. Software-calibrated, features a backlit LCD, internal rechargeable batteries and internal charge regulator. Uses a Basic Stamp II.

Accelerometer: A handheld vibration meter, to measure how much those poorly balanced machines are shaking!

GPS-based frequency standard: Using an inexpensive GPS board, it provides atomic clock frequency accuracy to an HF transceiver, and lab equipment.

Quick and dirty Geiger counter: Check whether it's still safe to breathe!


Controller for rotary film processor: If you want to develop your color film, and specially slides, at home, here is the machine you need!

Mercury battery replacement: Many old cameras and other devices used mercury batteries, which are no longer available. Here is an analysis of the 
problem, and a few solutions.

Gadgets for the home

Plant watering timer: It's time to automate the watering of your garden, balcony, or that azalea in your living room!

Room heating controller: Tired of mechanical thermostats that overshoot the set point and make you waste expensive energy? Here is a phase-control device that works well and is simple!


KISSCAD: My very own schematic drawing software. Released as freeware.

Tutorials and other stuff

Transformers and coils: This is not a building project, but a short and concise lesson in how to design electromagnetic parts. It's much simpler than what you may expect!

Practical transformer winding: The title says it all! It includes a transformer design spreadsheet, and AWG wire table.

Ferrite core loss in HF power applications: My own loss measurements on several types of ferrite in the 1.8 to 54MHz range

Thermal design: A short course in keeping electronic parts adequately cool.

Control loops: If you never managed to understand control loop theory from highly mathematical textbooks or courses, maybe this will help you!

RF power amplifier design: An almost book-size article aimed mostly at HF amplifiers.

Multimeters: Which multimeters I use, and why.

The wailing wall

The Power Jack 3500W inverter exposed: A shining (and smoking!) example of poor engineering! 


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