Home security and teleguard circuits
Summary :
Table of Contents
- Introduction
- How to use the telephone as an electronics eye
- Four major units of this project
- Black diagram
- Circuit diagram
- About microcontroller interface unit
- Description on dialer circuit
- Features of ISD1420 digital voice processor
- Conclusion
- References
Abstract
In this project, we show how we can use the telephone as an electronics eye. With the help of a landline phone, we check and examine the position of the house automatically. In this logic, we attach some sensors with the telephone and if there is any miss-hap, the telephone is automatically switched on. This circuit warns the user against fire accidents. It relies on the smoke that is produced in the event of a fire. When this smoke passes between a bulb and an LDR, the amount of light falling on the LDR decreases. This causes the resistance of LDR to increase and the voltage at the base of the transistor is pulled high due to which the supply to the COB (chip-on-board) is completed. The signal generated by COB is amplified by an audio amplifier. In this circuit, the audio power amplifier is wired around IC TDA 2002. The sensitivity of the circuit depends on the distance between bulb and LDR as well as the setting of preset VR1. Thus by placing the bulb and the LDR at appropriate distances, one may vary preset VR1 to get optimum sensitivity. An ON/OFF switch is suggested to turn the circuit on and off as desirable. This proximity detector using an infrared detector can be used in various equipment like automatic door openers and burglar alarms. The circuit primarily consists of an infrared transmitter and an infrared receiver. The transmitter section consists of a 555 timer IC functioning in a stable mode. The output from a stable is fed to an infrared LED via resistor R4, which limits its operating current. This circuit provides a frequency output of 38 KHz at 50% duty cycle, which is required for the infrared detector/receiver module.
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