Q: What is GSM?
A: It stands for Global system for Mobile Communications. It is a communication standard using time division multiple access technique.
Q: What is the frequency range for GSM?
A: GSM frequency range is 900MHz
Q: How can I feed the mobile number?
A: By giving a missed call to the SIM number of the GSM interfaced to the controller, one can feed the mobile number.
Q: How energy tariff is calculated?
A: Energy tariff is calculated by using digital pulses from energy meter, an appropriate program calculates the pulses and converts it in energy units and then calculates the per unit cost.
Q: Which microcontroller is used in this project?
A: A 40 pin microcontroller from 8051 family is used in this project.
Q: Which energy meter used?
A: A 230VAC, 5-20A digital energy meter is used.
Q: How exactly is the pulse reading taken from energy meter?
A: From any digital energy meter internal circuit that delivers one pulse per a certain fraction of one unit is taken from its blinking LED points.
Q: What is the formula for calculating smoothing capacitor value?
A: There is some approximated formula .Peak to peak ripple voltage = Load current in amps / (2*line frequency in hertz *capacitance in farads). But as rule of thumb for 1 A current 1000uF is best. Thus it is load dependent.
Q: Why did you set sending of SMS for only 10 pulses?
A: We can write the program for monthly or weekly or daily basis, but we cannot wait for that much of time to see the output or we cannot wait for 3200 pulses which make 1 unit. Also here our load is 100W bulb so we have to wait for 10 hours to get 1 unit. So we go for 10 pulses to send SMS.