Simple Home Alarm Circuit Using 555 IC39
This is a Simple Home Alarm Circuit Using 555 IC's . This circuit can be simplified by using a single 74C14 IC. This IC is also known by the following numbers: 40106, 40014, and 74HC14. These are CMOS chips and are characterised by low current consumption, high input impedance and a supply voltage from 5v to 15v. (Do not substitute 7414 or 74LS14. They are TTL chips and operate on 4.5v to 5.5v and have low impedance inputs.) Simple Home Alarm Circuit Diagram The 74C14 contains 6 Schmitt Trigger gates and 4 of these gates (Schmitt Inverters) are used in this circuit. The circuit consists of a number of "building blocks" and the first consists of two transistors in a very clever "bootstrap" arrangement. The first transistor is turned on via the 3M3 and 47k. The second transistor is not turned on and the output is HIGH. A small signal from the electret microphone will consist of positive and negative excursions and the negative excursion will turn the first tran...