| |
Circuits of the Week
Last Updated on:
04/27/2008 06:18 AM
(Dec 2007 - July 2007)
(June 2007 - Jan 2007)
(Dec 2006 - July
2006)
(June 2006 - Jan 2006)
(Dec 2005 - May 2005) |
| |
|
| June 24, 2007 |
Interference Free Switch Mode Pre-Regulator
Designed by Andrew R. Morris morr3763@bellsouth.net I created this circuit to fix an overheating problem with a small Chinese-made stereo
set. This simple solution to a perplexing problem worked so well that I felt the need to share it. This circuit can be used for other applications as well. |
June 17, 2007
Happy Father's Day |
Three Volt Low Battery Voltage Flasher
This circuit is designed to monitor two alkaline cells (3v) that form the battery often used in portable electronic equipment. It use an inexpensive IC from Panasonic that is connected to an
efficient LED flashing circuit. When the battery voltage drops below a certain point the circuit flashes the LED. In the off state the circuit draws only 1uA, while in the active
flashing state it draws 20uA. Published in EDN, Jan 2, 1997 |
| June 10, 2007 |
Voltage to Frequency Converter + 1us LED Pulse Driver
This circuit receives the signal from the above amplifier and launches powerful 1uS infrared light pulses from a low cost LED that are frequency modulated by the audio information. The 10KHz
center frequency of the pulse stream is low enough so a standard infrared LED can emit ten times more light than conventional long pulse techniques. The circuit is described in more detail in the
transmitter section of Dave Johnson's Handbook of Optical Through the Air Communications. |
| June 3, 2006 |
Fully Isolated 50/60Hz Sync Generator
This circuit will produce a single pulse at the zero voltage cross points of the power line voltage. An opto-coupler provides a very safe 5KV isolation. |
| May 27, 2007 |
1 Amp Current Injector
When you need to measure resistance down to a few micro ohms, this circuit works great. It is powered from two "C" cell batteries and is designed to inject a well-regulated one amp of current into
the unknown resistance. By measuring the voltage drop across the resistor with a digital voltmeter, the resistance value can be accurately measured. The circuit also is equipped with a low battery
monitor. |
| May 20, 2007 |
40KHz Light Detector with Sunlight Immunity
The circuit below was designed to turn on an external 12v relay, whenever it detects light from a nearby LED light source, modulated at 40KHz to 50KHz. This
circuit was originally designed to operate from a fast moving vehicle. The light transmitter was positioned at a stationary position, while the matching receiver was mounted on the vehicle.
The circuit has high ambient light immunity and in most cases, can operate in direct sunlight. |
| May 13, 2007 |
Medium Power 125khz Oscillator
This circuit is similar to number 117 but adds more invertors in parallel to deliver more power. The values shown are for 125KHz. |
| May 6, 2007 |
Universal LED Flasher
This low power LED flasher circuit draws about 100ua from any DC power supply ranging from 3 volts to 24 volts. The 1.0Hz 10ms LED pulsed current is held to a constant 10ma. |
| Apr 29, 2007 |
Ultra Low Power Latching Relay Circuit
The circuit below takes advantage of some inexpensive small super capacitors. The circuit pumps 6 volt pulses into the separate 5 volt latching and unlatching relay coils. A short 25ms
pulse is all that is needed to flip the relay states. A third super capacitor is used to supply a higher peak current than a small lithium cell might otherwise be able to supply. |
| Apr 22, 2007 |
Miniature Lighthouse Light Simulator
The circuit I came up with is shown below. It uses two dual low power op amps. The first two devices form a classic oscillator circuit whose output is a triangle waveform signal.
That signal is routed to a current regulator circuit, which converts the triangle voltage signal to a triangle current signal through the lighthouse LED. A third op amp generates pulses timed so
they occur at the peak of the triangle waveform. The result is a LED, which gradually grows brighter, then flashes even brighter before dimming again. This should produce a light, which
simulates a rotating lighthouse light. |
| Apr 15, 2007 |
Electrical Device Harvests Earthworms
A 120vac or 240vac isolation transformer is used to force earthworms from the ground. |
| Apr 8, 2007 |
Automotive Electrical Voltage Indicator
This circuit will indicate if an automotive electrical circuit has zero volts or 12 volts present. |
| Apr 1, 2007 |
60 Watt Lamp with Auxiliary 14v LED Lamp
This circuit controls power to a standard 60 watt lamp plus generates an auxiliary 14v DC supply which can power an automotive style 12 LED array. |
| Mar 25, 2007 |
Wave Power Generator Demo System
An inexpensive stepper motor is used as a voltage generator in this wave generator demo. |
| Mar 18, 2007 |
60 Watt Lamp with Auxiliary 14v LED Lamp
This circuit controls power to a standard 60 watt lamp plus generates an auxiliary 14v DC supply which can power an automotive style 12 LED array. |
| Mar 11, 2007 |
Wire Security Loop Alarm
A wire loop is used to protect valuable objects in this alarm circuit. The circuit is powered by a 9v battery. |
| Mar 4, 2007 |
Fake Car Alarm Light
Whenever the car’s ignition is turned off, this circuit activates a flashing LED, which can be positioned to appear as an active alarm system. |
| Feb 25, 2007 |
Motion Alarm Using Piezoelectric Device
An inexpensive piezoelectric device is used as a motion sensing device for this motion alarm. |
|
Feb 18, 2007 |
Project Dragon Fish: Joe Takes Rocket Science to New Depths
Joe Peck has extended the pursuit of realism in model rocketry to the launch environment. Think Poseidon here — this rocket launches from underwater. Initially, it's sealed watertight from nose to
nozzle. Ignition is triggered by bringing a magnet close to a sensor contained in the upper section. The motor ignites, blowing off the bottom end cap and we have liftoff! If you're into model
rocketry, here's your next challenge. |
| Feb 11, 2007 |
555 Timer Forms Simple PWM Motor Controller
Using a CMOS version of the 555 timer, this circuit can be used to control the speed of a motor by adjusting the duty cycle of the pulses sent to the motor. |
| Feb 4, 2007 |
Low Voltage H-bridge
TTL type Q and inverted Q inputs control a classic H-bridge circuit, rated at 50 volts and about 10 amps. The circuit can control power and direction of a DC motor. |
| Jan 28, 2007 |
120vac/240vac Indicator
Two LEDs indicate if a power line has 120vac or 240vac voltage on it. |
| Jan 21, 2007 |
120vac Low Voltage Alarm
This circuit will activate a beeper alarm whenever the AC line voltage is less than 100vac. |
| Jan 14, 2007 |
18v AC to DC Power Supply
This is a classic linear power supply which produces a regulated 18v, rated at about 1 amp. |
| Jan 7, 2007 |
Laser Used as Vehicular Traffic Counter
This is an illustration how a laser could be used to count traffic and measure the speed of each car passing through the sensor area. |
| Dec 31, 2006 |
Check Engine Beeper
When wired into a car’s indicator light panel, this circuit will turn on a loud beeper when the “check engine” light turns on. |
| |
(Dec 2007 - July 2007)
(June 2007 - Jan 2007)
(Dec 2006 - July
2006)
(June 2006 - Jan 2006)
(Dec 2005 - May 2005) |
