hi master, i want to ask something about module blutooth hc-05. can bluetoothh hc-05 connect or control morethan one device ? ( i want to use control 1 lamp with 2 or more android with module hc-05+arduino). what should i do ? make the hc-05 become master ? but what kind type bluetooth of android ? master or slave ? thanks for ur help 
You can connect several Android devices to the HC-05 but you can only connect one at a time. Each Android device you want to use has to be paired with the HC-05 and the HC-05 can be paired with up to seven devices (I think it is seven. Somebody please correct me if this is wrong).
If you want to simply turn the lamp on and off then start by searching for one of the many turn an LED on/off guides on the internet. This will get you started with the software.
You don't say what kind of lamp. If it is mains, 110/240v, then there are other considerations and other people here can probably help.
I have a couple of brief guides that may help
Turning a LED on and off with an Arduino, a HC-06 and Android
arduinoBTcontrol
The Android apps are written in MIT's app inventor and are fairly basic but should be enough to get to started.
hc-05 and hc-06 communicate http://make.robimek.com/two-arduino-communicate-with-bluetooth/
MartynC:
d the HC-05 can be paired with up to seven devices (I think it is seven. Somebody please correct me if this is wrong).
I believe this is correct but I also believe it just means there are seven slots in an address book for Arduino to use, and I don't think it helps much here.
I first thought this exercise would be extremely difficult, with the biggest problem at the Android end, but I now think it might be very simple, with no problems at all at the Android end.
The HC-05 can only talk to one Android at a time. The exercise therefore becomes one of ensuring the HC-05 is open for conversation whenever it isn't actually in conversation already.
This can probably be done by adapting MartynC's programme and the wiring to HC-05. By this I mean the power supply is either from, or controlled by, a programmable pin on Arduino. The programme might simply include an addition whereby any valid command signal is followed by a short LOW on the power pin thereby breaking the connection and thus making HC-05 available for another, or even the same, Android to establish communication. All that is required is that the Androids have been previously paired in the normal manner.
Note that I make no claims for the practicality of this. I don't even think it's a good idea. But I do believe it's possible, and even easier than one might first think.
edit
That Robimek guy doesn't know what he is doing but he might have something useful hidden away somewhere on his site.