hi tonmoy,
A few more operational questions.
Do you want the door detector to work from both sides of the door?
That is incoming/outgoing.
What type of door is it?
The reason for asking is, how important is it that the detector/circuit opens the door every time without fail.
Example 'a fire exit door' [ I hope not]
Internal/External door, swing door, sliding door ????
If you design your own door open/close electrics/mechanism, which is not an easy task, remember the detection system has not only to detect someone approaching the door,
BUT to stay open while the person maybe just standing in the doorway.
Eric