Q: Which microcontroller is used in this project?
A: A 40 pin microcontroller from 8051 family is used in this project.
Q: What is DTMF based garage door opening system?
A: DTMF based garage door opening is controlling the movement of garage door through DTMF tones from cell phone.
Q: How is a real door demonstrated in this system?
A: As a sample, a CD loader demonstrates an actual door
Q: Can one use it with landline?
A: Yes it can be used with landline phone
Q: Can it be used with mobile phones?
A: Yes it can be used
Q: What is DTMF?
A: DTMF or Dual tone multi frequency is a signaling system which uses a combination of two frequency tones to represent a key pressed on the keyboard of any cell phone.
Q: What is the DTMF IC used?
A: IC 8870 is the DTMF IC used.
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 my phone is not working for the project while it works with other phones?
A: The dialing tones generated by a phone forms as an input to the project for proper working. While some phones develop exact DTMF tones even before establishing a call while pressing the numbers, some other phones develop a flat tone for any number pressed. Besides the same, some phones the internal speakeroutput is not disabled owing to some specific setting enacted by the user. In these cases directly dialing through chord connection shall not work. However if a call is initiated to the dialed number mobile which is interfaced to the project it will work (provided the connector is not loose) as DTMF tones are compulsorily made available to the receiver from the exchange ,as all our IVRS works on those kind of tones. Therefore,if the project does not work by direct wire connection please try by dialing the number from any other phone. In order to be doubly confirmed make sure that while one inserts the pin to the cell phone the speaker gets disconnected failing which it is not going to work because the tones are sent to the project board only if the speaker of the cell phone is disabled.