This project allows remote control of equipment via SMS text messages sent to a microcontroller connected to a GSM modem. The microcontroller can control up to 8 external devices based on plain text commands like "pump on". It also enables setting automatic schedules to turn devices on and off. The hardware includes an 8-bit microcontroller, GSM modem, relays, RS232 converter, driver IC, and power supply. The software tools are Keil Cross Compiler, Top-View Simulator, and a flash programmer for the microcontroller.

1. GSM Based Automatic and Manual Device Switch
Abstract:
Short Message Service (SMS) is defined as a text-based service that enables up
to 160 characters to be sent from one mobile phone to another. In a similar vein
to email, messages are stored and forwarded at an SMS centre, allowing
messages to be retrieved later if you are not immediately available to receive
them.
Using the convenience of SMS, this project lets you remotely control equipment
by sending plain text messages, such as "pump on", "aircon off", and “reset" or
"light1 on" – all of which can be pre-programmed into the controller and easily
remembered later. It can control up to eight external devices. Also, you can set
time to set a device ON and OFF, which will operate the devices automatically.
Here, an 8-bit microcontroller is used to control the whole circuit. It read
message from the GSM module and control the devices according to the
received message.
Hardware Requirements:
1. AT89C51RD2.
2. GSM Modem.
3. Relays.
4. RS232 (TTL to RS232 Level Converters).
5. ULN2003/ ULN2803 (Driver IC to Connect microcontroller to Devices).
6. Power Supply Section.
Software Tools:
1. Keil Cross Compiler.
2. Top-View Simulator.
3. Flash Programmer for Microcontroller.