Alam Circuits


Hacks and Mods: VFD Talking Alarm Clock

Are you having a hard time waking your hubby from sleeping? And when you leave the house for work, are you in doubt that he has not gotten out of bed? One thing that will stop your worries is to use this clock that does not just tell time but also “swears”. This is an […]


Simple Darkness Activated Alarm

Most darkness activated alarms employ opamps and some logic ICs. Here, a less expensive approach is shown based on the eternal 555, this time in monostable multivibrator mode. Components R2 and C1 represent a one-second network. When the LDR (light dependent resistor) is in the dark, its resistance is high, pulling pin 2 of the […]


Drinking Water Alarm

The State Jal Boards supply water for limited duration in a day. Time of water supply is decided by the management and the public does not know the same. In such a situation, this water alarm circuit will save the people from long wait as it will inform them as soon as the water supply […]


Speed Alarm For Cars

In normal suburban driving you pass through so many different speed zones that it can be a nuisance having to switch speed settings. The speed display can also be a distraction. This circuit eliminates the display and the need for speed selection. Each time you exceed a particular speed setting (eg, 40km/h, 50km/h, etc), a […]


Overheat Detector Alarm/Switch

At the heart of this circuit is a precision integrated temperature sensor type LM35 (IC1), which provides an accurately linear and directly proportional output in mV, over the zero to +155 degrees C temperature range. The LM35 develops an output voltage of 10 mV/K change in measured temperature. Designed to draw a minimal current of […]


Mains Failure Alarm

This circuit was designed to produce an audible alarm when the mains power is interrupted. Such an alarm is essential for anyone whose livelihood depends on keeping perishable foodstuffs in cold storage. The circuit is powered by a 12-V mains adapter. LED D5 will light when the mains voltage is present. When the mains voltage […]


LDR & LED Pair Smoke Detector and Alarm by LM1801

Smoke detectors are generally used in advanced alarm systems. Most of this professional devices use gas-detectors, ionization rooms or radioactive elements as sensors. In this circuit we are not using any of this complicated components. Instead of these, we are using two LDRs and one LED.LM1801 special-purpose IC ,which is designed especially for smoke detectors, […]


Photodiode Alarm

This Photodiode based Alarm can be used to give a warning alarm when someone passes through a protected area. The circuit is kept standby through a laser beam or IR beam focused on to the Photodiode. When the beam path breaks, alarm will be triggered. The circuit uses a PN Photodiode in the reverse bias […]


Gas Leakage Alarm

LPG gas is supplied in pressurized steel cylinders. As this gas is heavier than air, when it leaks from a cylinder it flows along floor and tends to settle in low spots such as a basement. This can cause fire or suffocation if not dealt with. Here is a circuit that detects the leakage of […]


Simple Alarm System

The circuit presented here is a very simple and yet highly effective alarm system for protecting an object. The circuit requires no special devices and can be built using components that you will no doubt be able to find in the junk box. The alarm-triggering element is a simple reed switch. To generate the alarm […]