Hi Barry,
The power 12V to the relay, I removed it to see if the coil affect anything, and I changed it like a switch. But unfortunately, when I turn ON the switch, it act like short circuit and make my 8051 system failure.
Look at the two 12V supplies, if I used only one 12V supply, when relay turns ON, 8051 system totally failure and no response. I am now changing to use two separate 12V, (2 transformers), when relay turn ON or OFF, it will give a false signal to 8051 to move to next step, but at least now 8051 is not failure.
I have no idea how this could happen, they are like two separate individuals system, but when put them together they are not co-operate well.