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This Home Alarm System is simple, secure, fast and cheap. It's only few components with maximum security with Rolling Code TX and Shock Sensor with variable sensitivity. The alarm module can be assembled in only 2 hours and it don't need manual preset.

Home Alarm System with this characteristics is the most cheap system and the total cost could be reduced using a normal external sounder (escl. AG8).GSM module will be add in the future for a remote control.

The blue led connected to the pin RA3 of micro controller is used like a memory to know if the home alarm system has been activated by an event and its reset after a reactivation. The red led connected to the power supply before the 1N5406 diode is used to check the power supply connection. Of course the other 3 micro led red near the relays are used to check the output state.

Here you can download the last version of The Home Alarm System date 10 July 2007:

Home Alarm System in detail

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Here's a temperature data logger circuit, an 8-pin microcontroller based circuit for temperature data logging via the serial port of any computer from between 1 and 4 remote digital temperature sensors, DS1820/DS18S20 made by Dallas.

Features of the Temperature Data Logger are are follow:

Provides realtime data via the serial port.
Interfaces up to 4 x DS1820 sensors.
Accuracy to 0.5 degrees centigrade
Fahrenheit scale selected by a jumper
No external power required
Data stream easily logged & processed.
Over 200m distance for each sensor

The sensors of temperature data logger may be located more than 200 yards from the PCB. Just check that the remote VDD is above 4.4Volts. It's recommends 10uF tantalum capacitors be placed across the power supply pins (not supplied) to minimise random errors and possibly get increased range.