Alarm

Using a piezoelectric element for alarm applications offers low cost, low power, and flexibility. By coupling this element with a 12C508 programmable controller (Microchip Technology, Chandler, AZ), you can implement an eight-pin alarm generator. This approach provides multiple driver formats with a minimum of additional cost and footprint...

This project is a standalone simple home security monitoring project that will trigger a buzzer when the magnetic contact is opened...

This project is a power supply monitoring device that will trigger a buzzer when the mains supply cuts off. At the same time, the light emitting diode will turn ON...

Construct a 6-15V Alarm by using LM/NE 556 dual timers. It will generate a noise level of 90db-110dB range...

Schematic and parts list needed to construct a simple Light Alarm. Use this to protect your medicine cabinet, cash drawer or any cabinet...

A while ago I got an email asking for the schematic of a circuit to detect cut phone lines. It didn`t take me long to find this circuit in Electronics Now. When the circuit detects that a phone line has been cut, it activates a MOSFET which can be used to drive a relay, motor, etc. It can also be connected to a security system. # The "Load" can be a relay, lamp, motor, etc. The circuit can also be connected to a security system to sound an alarm in case the phone line is cut. If the circuit is connected to a security system or other circuit, both circuits must be electrically isolated from each other using an opto-isolator, relay, etc. This also means that the Cut Phone Line Detector must be powered by a seperate 9V supply...

This is the lowest cost dialing alarm on the market and shows what can be done with an 8-pin microcontroller. The complete circuit is shown below. You cannot see all the features of this project by looking at the circuit - most of them are contained in the program. So, read on and see what we have included. Dial Alarm-1 has a single input (although a number of sensors can be placed in parallel on the same input line). The circuit requires a trigger pulse to turn on a BC 557 transistor. This delivers power to the microcontroller. The micro starts to execute the program and outputs a high on GP2 to keep the "turn-on" circuit active. It also turns on the LED in the opto-coupler and this causes the line to be "picked up" via a high-gain Darlington transistor. The micro then dials two phone numbers and executes a series of events to alert the called party of an intrusion...