GSM Remote Control Temperature Control Schematic

Posted on Feb 5, 2014

The full GSM thermostat is managed by a Microchip PIC18F46K20-I/PT microcontroller, programmed with a firmware that controls the temperature and takes care of the communication with the GSM module which is the component named GSM; this is, in fact the small board hosting the cell, so the pins` numbers refer to the used pin-strips` contacts. The fi

GSM Remote Control Temperature Control Schematic
Click here to download the full size of the above Circuit.

rmware reads the room temperature by means of a smart probe Dallas DS1820, it controls the logical condition of the opto-isolated input and commands the relay when needed. Having said that, let`s now take a look at the electric scheme, starting by the power block, that from the input voltage (power applied to PWR, + and must be a continuous current at a value between 5 and 32 V) gets a stabilized component of 3. 6 V width by means of a switching regulator. The input voltage is filtered at the bottom by the diode protecting against polarity inversion (D1) through condensers C1 and C2. Fuse F1 enables you to protect both the circuit and the power source in case of short circuit in the integrated regulator discussed below. The regulator is a U1 (a MC34063) and acts as a DC/DC converter step-down; it is used in the classic configuration of the series PWM regulators charged by inductance, whose output voltage depends on the energy stored in L1. The voltage it provides is stabilized providing feedback to the DC/DC through the demotion of a portion of the leveled component by condensers C4 and C5, made by the resistive divider R2/R3. The 3. 6 volts present in these condensers are widely filtered by other condensers placed on the power lines of the microcontroller and of the GSM module; which presents, during transmission, absorption peaks compensated for by C7, C8, C13, C14, C15 and C16, thus avoiding than an impulsive current...

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