Electronic Projects, Circuits, and Devices

Here are some nifty little projects that are useful for tasks in the workshop or home, as well as some that are more decorative. Some of the articles help beginners with simple circuits, whereas others delve into details on specific microcontroller chips.

Model rocket liftoff Model Rocket Launch Controller
The secrets to a successful launch controller are thick cables, power through a relay, and a beefy battery (such as a lead-acid motorcycle battery). Learn what is inside a low-end commercial rocket launcher, how to make your own simple launch controller, and take a look at a fancy rocket controller that includes covered pilot switches and a switch lock.
Tiny thumbnail graph of weather in Chicago Weather Station
Logging six temperatures and solar activity at one minute intervals around the clock using a 4 megabyte serial flash chip. The observation results are graphed to demonstrate weather conditions over multiple days in the Chicagoland area. Ran into some problems with a broken wire, overheating project box, shadows, and exposed sensors.
LED bar graph for a water softener salt-level monitor Water-Softener Brine-Tank Salt-Level Monitor
If you have hard water, did you ever forget to add salt to the water softener tank? This electronic device monitors how full the tank is using a Sharp DP2D12 infrared distance monitor. The results are displayed on a custom wall plate with a multicolor LED bar graph. The project also includes several photosensors to save power.
A ring light attached to a magnifying glass Miniature Surface-Mount LED Ring Light
Ring lights provide shadowless all-around lighting that is particularly useful for close-up work such as macro-photography and circuit-board inspection with a magnifying glass. This project also includes instructions on soldering surface-mount electronic components and machining a circuit board into a ring (round/circular/donut) shape.
Pumpkin with LED Candle Halloween Pumpkin with Colorful LED Candles
Extensive tutorial on putting blinking LEDs and different colored LEDs into jack-o-lanterns. Includes schematics, solderless breadboard photos, and three movies (the blue pulsing LED is my favorite). Great way of getting started in electronics! Although this was written for Halloween, the techniques are applicable for Christmas votive candles as well.
LED tester lighting up a red LED Standalone LED Tester
Description and schematic for a constant-current LED tester. It safely lights up standard through-hole and surface mount LEDs, while providing easy access to current and voltage measurements.
Temperature displayed on 4-digit multiplexed blue LED display Dual Fan Controller
A birthday present gone too far. An overengineered temperature-based automatic twin fan controller with brass face to keep a kitchen PC cool.
Toggle switch with safety cover Fighter Pilot Safety-Cover Toggle Switch
See how an illuminated toggle switch works by breaking one open and putting it back together. Most of these are automotive switches, which need 12 V. The circuit schematics on the second page of the article show you how to shift voltage levels from 12 V to 5 V, and 5 V to 12 V. A microcontroller can read the switch state and blink the LED.
Two digit 7-segment numeric display showing the best trim value for a reasonably accurate internal oscillator on this particular 68HC908KX8 microcontroller chip. Trimming the Internal Clock on a KX8 Microcontroller
Example algorithms for manually or automatically tuning the oscillator on the internal clock generator of the popular MC68HC908KX8 microcontroller. Also includes batch test results and a video.
A analog light or object sensor with red and green LEDs Analog Comparison, Digital Result
Comparators are very useful for comparing two analog voltages and providing a digital result. In this case, if the light source is dim, a red LED is enabled. If the light source is bright, a green LED is enabled. However, once comparators are understood, they can be useful for driving small robots or helping a microcontroller.
A montage of images from the Lite-On multifunction LED display Multi-Segment LED Display
Lite-On LTM-Y2K19JF-03 is a surprisingly good LED display with alphanumeric, numeric, and icon LEDs. The LED module includes all driver circuitry -- no additional transistors or resistors are necessary. The article also describes how to create and edit a 14-segment alphanumeric LED font using Excel.
Logic analysis of TWI problem Atmel TWI
Explains an I2C multi-master bus issue on the Atmel AVR 8-bit microcontrollers. Shows logic analyzer traces of TWI (two-wire interface).
Alphanumeric LED Display Project thumbnail Alphanumeric LED Display Project
A phenomenal 256-diode ROM acts as a character generator for a two-digit hexadecimal display.
Infrared Transmitter Project thumbnail Infrared Transmitter Project
The heart of this project is a NAND gate turned into a 40-kHz oscillator. A simple 9-volt to 5-volt regulator circuit schematic is also included.