555 Circuits


Edge-Triggered 555 Monostable Multivibrator

While the 555 oscillator IC is a very versatile device, it can also be quite tricky and solutions are not always obvious. Such is the case with this edge-triggered 555 monostable circuit. By differentiating the trigger signal, the monostable multivibrator times out normally regardless of the trigger signal length. 555 Schematic 555 datasheet More than […]


Power Failure Alarm Circuit

This minuscule power failure alarm circuit is a power supply monitoring device that will set off a piezo-speaker when the ac mains mains supply cuts off. It is very helpful to indicate the loss of power supply to some power-critical instruments such as a lifecare device installed in a hospital. Alarm activation at the right […]


Sound Activated Motor Driver

If you are looking for an idea to build your own simple electronic gift, your search may end here! Described is a minimalist design for you, realized using a handful of discrete components. The major component in this design (Sound Activated Motor Driver) is an inexpensive, and widely available robotic motor, which is nothing but […]


1.5V 555 LED Driver Experiment

This 1.5V 555 LED driver is more of a fun learning experiment than a practical circuit. While the TLC555 can indeed drive a 3V white LED using the inductive discharge technique, it typifies the kind of problems present in low voltage circuits. Two circuits are presented: Basic 555 LED Driver and Bootstrapped 555 LED Driver. […]


Energy Saving Lighting with One-Shot Timer Circuit

Faced with the situation to control the time that the light is turned on, engineer Radu Preda from Romania has started experimenting with different circuits to save money spent on electricity. He has designed 2 energy saving lighting circuits, the first one uses a relay and the second one uses a optoisolator triac MOC3041 and […]


Door Opening Alarm / Alert Circuit

The door opening alarm circuit or “Front Office Visitor Alert” is used for alerting you when a customer is at your office/shop. It will produce a beep sound when each new customer or visitor is entering, and will automatically switch OFF after few seconds. Schematic of the Door Opening Alert Circuit 555 datasheet In this […]


Two-Door Buzzer with Display

The Two-door Buzzer with Display is applicable and well suited to be used in a house having two gates or doors that are distant from each other. It helps the person inside the house by providing an alarm and a number display determining which door where the visitor is. It also saves time and effort […]


Dew Heater Controller For Telescope

Dew (condensed moisture) is one of the astronomer’s worst enemies, and all telescopes are subject to the dew problem. If no precautions are taken, it can easily destroy a perfect observing night, as it forms on mirrors and lenses, thus it is required for almost every amateur astronomer to have some kind of dew control […]


Crazy Multicolor Flashing LED Globe!

Nowadays, single-color and multi-color flashing LEDs are easily available, which obviates the requirement of external chips to produce fascinating lighting effects. What can we do with one piece of such a single color flashing LED, and two pieces of multicolor flashing LEDs? Here is an ultrasimple circuit of an LED Globe wired around the evergreen […]


Zener diode tester module

Diodes whose reverse-breakdown characteristics are controlled precisely during manufacture are called as Zener diodes and are intended specifically for operation in the reverse breakdown mode primarily as inexpensive voltage references. An uncomplicated circuit application of a ZD is the common shunt voltage regulator. If you have a Zener diode (ZD) of unknown characteristics or if […]