Simple Mat Alarm Switch

This easy to built circuit produces a warning beep when somebody crosses a secure area in your home or place of work. The transfer, hidden beneath the ground mat, causes the alarm whilst the individual walks over it.

The circuit makes use of a behaviorive foam because the switch. it may be? small items of behaviorive pads usually used to pack delicate ICs as antistatic cover. then again, you’ll be able to make the switch via coating conducting carbon ink on two small items of a copper-clad board.

When the circuit is in standby way of mode, transistor T1 does no longer conduct, for the reason that its base is floating. When the person walks, the switch is pressed and present flows via R1 and the transfer to provide certain bias to transistor T1. Transistor T1 behaviors and its collector voltage drops, which acts as a terrible cause input for the monostable stressed out around IC NE555 (IC1). 1 outputs a pulse of fifty-seconds period with preset values of R4 and C3. This pulse is carried out to the buzzer via transistor T2. The buzzer sounds a caution beep on unauthorised access. the pulse duration can also be modified to the required worth by changing the prices of R4 and C3.

Resistor R2 in the circuit makes the cause pin of IC1 high to stop fake causeing.

compile the circuit on a general purpose PCB and enclose in a plastic case. Use a 9V battery to power the circuit. connect the contactpad switch with the PCB and hide under the mat at the front. The PCB will also be fixed on the nearby wall.

Make the switch carefully the usage of conducting foam or copper clad lined with behavioring ink. place the two pieces with their habitsing surface going through each different. Solder moderately a skinny copper electrical wire and make sure that it makes contact while the two plates contact in combination on urgent. provide? 1cm rubber tabs between the plates to steer clear of touch in the standby mode.