Refrigerator door alarm circuit with two 555 timers

This refrigerator door alarm circuit alerts you when the door has been left open. Very important, because the power consumption increases when this happends. It uses the popular 555 timer IC

Fuel Pump Cut-off Circuit

Fuel pump cut-off circuit for the car prevents the activation of the pump. Useful to increase the security level of a car which already has an alarm installed

Motorcycle Alarm circuit with transistors and relay.

This alarm has, as main elements, 3 transistors, a relay and various sensors, including motion sensors.

Electronic Doorbell Circuit using a 555 timer and a CD4017 decade counter

Electronic Doorbell circuit that lets know that someone is at the door. Made with 555 timer and 4017 decade counter allowing to change the tone of each note

Doorbell for Deaf People.

When a deaf person is alone in a house, it would be very difficult to realize that someone is knocking on the door without any visual warning signal.

Burglar alarm using thyristor and relay

This is a simple Burglar alarm uses a thyristor as the main element and a relay as the output device. The relay can activate a buzzer or a siren.

Temperature Alarm using thermostats

This simple alarm with thermostats circuit can be used on places where we must detect overheating. It uses 3 thermostats, and a one 2 contact, relay

Power failure alarm using transformer and relay

This power failure alarm circuit is very simple and is very useful when used with electric ovens, a refrigeration systems or to prevent a thief from cutting off the electrical power because it immediately warns of the problem. It also serves you when the fuses have blown.

This light sensitive alarm is very simple and works using, as main components, a transistor, an LDR and a relay.

The alarm activates when the illumination level changes from almost total darkness to a moderately high illumination level. When this happens the alarm is locked and the alarm signal, be it a light or a sound, remains active.

Main Power failure alarm and battery backup Circuit

This Main Power failure alarm circuit tells us when the electricity that powers a system or circuit, is gone.

Temperature alarm circuit with 741 operational amplifier

This temperature alarm circuit with operational amplifier activates a relay when the temperature of the place to be controlled exceeds a set level. Useful for an oven temperature control or a cooling system

Over temperature alarm circuit using Thermostat

This alarm circuit uses the 67L080 thermostat (TH) and can be assembled easily, due to the small number of components required.