solenoid rod with valve

anyone can help me how to connect the solenoid rod with the port 0 as an output port of 89c51 microcontrollor ,my project is to make door open system using keypad by entering password

Hi,

Obviously the I/O of your microcontroller can't provide enough current for a solenoid. You could use either a MOSFET transistor (driven itself by a small transistor, or CMOS/TLL logic) or a relay, also driven by a medium sized transistor. I assume that the solenoid will only be active for a short while...either to 'unlock' the door for a few seconds, or 'latch', that is, a single pulse unlocks, and a pulse locks.

Either way, the solenoid won't be active for long, so you could use a MOSFET, depending on current it would get hot, but unless its permentantly 'on' it sohuld be fine.

Blueteeth

A solenoid is usually the hard way to do it. Use a motor. Look at how it's done to lock/unlock a car door.

12 Volts dcoperated motorised solenoid is readily avilable meant for automobiles
avilable at automobile shop try this as it draws only 100 ma of current