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Topics - muthukrishnan

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I am planning to do a project which in its basic function can be divided into two blocks namely: A PIC BASED COLD ALERT TEMPERATURE SENSOR ALARM and A WARMING CIRCUIT using the DC operated heating Pads that is planned to be bought from Sparkfun. The PIC-based alarm is exactly as the one published in the "Everyday Practical Electronics" Magazine in July 2010 authored by David Clark.(uses PIC 16F627A)

What i have added on my own is to switch on the above mentioned heating pad (i.e) "electrically" (not physically by relay etc) by electrically connecting (short circuiting to pass current) the heating pad to the battery and that too by wirelessly sending a trigger (or) control signal (or) whatever signal suitable to achieve the intended purpose from an RF transmitter on the Alarm side by detecting  the alarm state (at a particular temperature set by programming the PIC) to the RF receiver module present on the heating pad side (whose output is used to "electrically" connect the battery to the heating pad.) For this, i have bought the WS TX-01 and WS-RX-01 modules working at 433MHz (ASK).

In short, the most important requirement is to provide a continuous DC supply (not intermittent as we pass a square wave as input to the heating pads) to the heating pads during alarm conditions and to entirely open circuit the heating pad from the battery "electrically" under no-alarm conditions.

Though i had thought many ideas for this control action such as using a 2 input AND gate with battery connected at one i/p and the control signal at other i/p (or) using a tristate buffer (or) a schottky diode rectifier etc, they encountered bottlenecks at some point on the circuit as I am quite unsure of how to control the "warmer" side exactly at the same time when the alarm state is detected by the PIC microcontroller.

That said, I am in critical need to implement the circuit practically as it is my final year project. But, still i could not arrive with a technically-correct circuit or idea of how to implement the "wireless switching of the heating pad" circuitry.
Please Please consider this post as a humble request to you all to help me out with a possible idea (or) suitable circuit to implement it practically as it would mean a lot of my heartfelt blessings for you.

Thank you for all. God Bless everyone... :)

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