cell phone signal activated led

A very simple and interesting project / schematic of a cell phone signal activated LED circuit. The circuit will light up an led when you call from your cell ph...

simple short circuit detection

This circuit is suitable in every situation where over-current protection is required. Here we give an example from the model train world. Every seasoned model ...

when the siren sounds

In Greek mythology, a siren was a demonic being (half bird, half woman). Later on this idea was transformed in art into a mermaid: a combination of a fish and a...

fridge door alarm circuit

This circuit, enclosed into a small box, is placed in the fridge near the lamp (if any) or the opening. With the door closed the interior of the fridge is in th...

room noise detector circuit schematic

This circuit is intended to signal, through a flashing LED, the exceeding of a fixed threshold in room noise, chosen from three fixed levels, namely 50, 70 & 85...

whistle responder schematic circuit diagram

This device beeps intermittently for about two seconds when a person in a range of around 10 meters emits a whistle. The first two inverters contained in IC1 ar...

keys finder

Imagine that is morning , you barely anticipate the bus for work and you can`t find your keys. If you suffer from this situation frequently, this circuit is ide...

broken charger connection alarm circuit

This circuit can be useful to detect if the load of any battery charger or plug-in adapter supply is not properly connected. The load can be a set of batteries ...

electronic door release

This circuit is designed to operate an electrical door-release mechanism - but it will have other applications. When you enter the four-digit code of your choic...

4 digit keypad controlled switch

This is a Universal version of the Four-Digit Alarm Control Keypad. I have modified the design to free up the relay contacts. This allows the circuit to operate...

cmos based vehicle anti theft alarm

This car alarm circuit features Exit and Entry delays, an instant alarm zone, an intermittent siren output and automatic Reset. By adding external relays you ca...

powerful security siren

A complementary transistor pair (Q2 & Q3) is wired as a high efficiency oscillator, directly driving the loudspeaker. Q1 ensures a full charge of C2 when power ...

mini alarm

This circuit, enclosed in a small plastic box, can be placed into a bag or handbag. A small magnet is placed close to the reed switch and connected to the hand ...

5 digit alarm control keypad

This Keypad is suitable for the Modular Burglar Alarm. However, it has other applications. Entering the First Four Digits of your chosen Five-Digit code - will ...

4 digit alarm control keypad

This Keypad is suitable for the Modular Burglar Alarm. However, it has other applications. Pressing a single key will energize the relay. Entering the Four-Digi...

enhanced shed garage alarm

This is an enhanced version of the simple Garage/Shed Alarm. The Entry and Exit delays have been increased to about 30-seconds - and I`ve added a timed Siren cu...

shed garage alarm

This is a basic single-zone burglar alarm circuit. Its features include automatic Exit and Entry delays - and an optional Siren Cut-Off timer. It has an extreme...

dozen small cmos alarm circuits

This is a selection of small self-contained alarm circuits. They have a very low standby current; and are suitable for battery operation. Some are triggered by ...

cmos 4060 burglar alarm

This is a single zone alarm - with automatic exit, entry and siren cut-off timers. It will accommodate all the usual types of normally-closed input devices - su...

simpler cmos single zone alarm

This circuit features automatic Exit/Entry delays, timed Bell Cut-off and System Reset. It will accommodate the usual normally-closed input devices (Magnetic Re...