[General] GSM based home automation

Hi guys..
I have done a project on sms based home appliances controlling. It is programmed such a way that when I send msg as @1 the bulb will turn on, similarly
@2- to turn off bulb
@3-to turn on motor
@4-to turn off motor
by default both bulb and motor is on.
when I send msg as @1, the reply will get back from gsm is "the bulb is already on".
when I send @2, the reply I get is "the bulb is off".
Everything is working fine but problem Iam facing is when I connect motor and bulb through relay , the reply I get from gsm is not proper, I mean even though the bulb is on , when I send @2, it gives the reply as "the bulb is already off". but when I test it without connecting relay, Iam getting correct output. What might be the problem..? Please help..

Use Opto isolator between micro and relay. Post your code.

For bulb send command @1 and for Motor @2. In code just toggle the device when its code is received. This way you only need one command per device. The micro will read the device port and send back the status.

Thank you for your response, the problem got solved. In the code instead of taking port pins directly , I have taken a variable then assigned variable to port pin..

It is better if you sense the current drawn by Bulb and motor to decice whether device is turned ON or not. If the device doesn't draw current on turning On then it means the device is open. The relay, relay driving transistor and relay contact may fail.