Originally posted by khali:
I bought a remote control car and put it near open window of sitting room.
I left the car on the sofa. I left the remote control on the table near open window.
However, in midnight, as I went to toilet, I saw the car suddenly charge forward by itself and landed on the floor. It then went on to hit the wall. I quickly pick it up and put it in the box. Nobody touched the remote control at all. The remote control was still on the table near the open window.
Can any electronics engineer tell me how come the car can move by itself when nobody touched the remote control? Is it normal?
I did a project before. The main reason is because the remote control car communicates with the remote control in bits via wireless. However, to confirm that the signal received is indeed from the correct remote control, there are certain set authentications between them. Only when the authentication signal is authenticated is the resulting information processed, and the car moves according to the information. However, there are presence of random signals in the air, and there's always a probability of a random signal giving the right authentication.
A mathematical example:
Supposed 8 bits were used as authentication. There will be 2^8 = 256 possible authentications... Which means there is a 1/256 chance of a random signal being able to authenticate with the car, and thus causing the car to move randomly.
Supposed 16 bits, there will be 2^16 = 65536 possibilities.
A better algorithm would be to include a Cyclic Redundancy Check. This further increases the number of possibilities, which will in turn reduce the probability of a random authenticated signal.
Sorry for the brief explanation... I didn't specialise into infocomm technologies, but hope you get the rough idea.
