GSM Remote Control 2 IN and 2 OUT Part 2 Schematic

Posted on Feb 7, 2014

The entire control is handled by a Microchip PIC18F46K20-I/PT microcontroller, programmed with a firmware that controls the GSM/GPRS module`s activity, reads the logic condition of the two opto-isolated inputs and sends commands to the two relays in the device. Having said that, let`s take a better look at the electrical scheme: power is supplied

GSM Remote Control 2 IN and 2 OUT Part 2 Schematic
Click here to download the full size of the above Circuit.

by continuous voltage, not always stabilized (applied to PWR, + and -) at a value between 5 and 32 V; such 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, which is necessary to obtain the 3. 6 V, needed for the rest of the circuit to work. The switching regulator U1 is based on a MC34063 chip, used in the classic configuration of the PWM regulators series, charged by inductance, whose output voltage depends on the energy stored in L1; the regulator is stabilized by the component demoted from resistive divider R2/R3, which is needed to set the output tension at 3. 6 V. The impulses produced by the inducer`s switching are then leveled by condensers C4 and C5. The 3. 6 volts at the bottom of the above mentioned condensers are then 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 that an impulsive current request may cause the microcontroller to be disturbed. The PIC is used in the configuration with an internal clock oscillator; both the scheme and the printed circuit are nevertheless equipped with external quartz, intended for those who want to modify...

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