This project uses a touchscreen to control electrical appliances in the home. The system has two relays that can control things like a light bulb and a fan. The control panel consists of a touchscreen that has been mounted on top of a graphical LCD. This touchscreen is used to send control commands via a

pair of wireless radio frequency (RF) communication modules. The touchscreen panel on the transmitter side is connected to a microcontroller, which sends on/off commands to the receiver, where the loads or appliances are connected. By touching the right spot on the touchscreen panel, you can use the wireless RF modules to turn the loads on or off from a distance. Circuit and how it works The system is made up of two parts: the transmitter and the receiver. The transmitter parts Fig. 1: Block diagram of the transmitter In Fig. 1, you can see a block diagram of the transmitter part. The microcontroller, RF Tx module, and graphics LCD are all powered by the power supply unit (GLCD) The microcontroller is linked to the GLCD. Since the touch screen is clear, it is put on top of the GLCD. The microcontroller takes the information from the touchscreen and turns it into a four-digit binary code. The encoder takes this code and turns it into a code that can be sent through the RF transmitter and antenna. Figure 2 shows a circuit diagram of the transmitter part. It is composed of several parts, including a transformer (X1), a bridge rectifier (BR1), a 128x64 GLCD (LCD1), a 4-wire touchscreen (TS1), a 5V voltage regulator

(IC1), an ATmega16A microcontroller (IC2), an encoder (IC3), a 433MHz RF transmitter module (TX1), an antenna (ANT.1), and a few other things. The microcontroller is directly linked to TS1. There are four wires on the touchscreen: X+, X-, Y+, and Y-. All of these wires are connected to the four analog-to-digital converter (ADC) pins on Port A of IC2. Wire X+ (pin 1) goes to PA0, wire X- (pin 2) goes to PA1, wire Y+ (pin 3) goes to PA2, and wire Y- (pin 4) goes to PA3. ATmega16A's Port B pins PB0 through PB7 are connected to GLCD's data pins D0 through D7. Since the ATmega16A has a 1MHz clock built in, there is no need for an external crystal. Switch S1 connects the RST pin 9 of IC2 to ground. Fig. 2: Circuit diagram of the transmitter When you briefly press S1, IC2 will be reset. The GLCD's control pins (RS, R/W, EN, etc.) are hooked up to Port D of the ATmega16A. Two chips in GLCD are controlled by control pins CS1 (pin 15) and CS2 (pin 16), which are each connected to pins 17 and 18 of IC2. The GLCD's reset pin (RST, pin 17) is connected to IC2's pin 19. Since the touchscreen's output is analog, the user has to turn it into digital. This is done by the ATmega16A's built-in ADC. Port A has an ADC built

in, so you don't need an external ADC chip (like ADC 0804). Encoder IC3 is linked to IC2's PC0 and PC1 ports. In both the sender and receiver circuits, all of the addresses from A0 to A7 of encoder IC3 and decoder IC5 are connected to ground. Pin 14 of IC3 is connected to ground for transmission. The bits are sent over RF signals from the output (DOUT) of IC3 to the data pin 2 of TX1. The transmitter part is easy to understand. When the user touches the "light on" symbol on the touchscreen, the resistance of the touchscreen changes, which changes the voltage across the touchscreen output. The ADC of the ATmega16 microcontroller takes this difference in voltage and turns it into a digital signal. ATmega16A looks at the range of X and Y coordinates. If it is in the range that has been set, it sets the output at Port C to what the user wants. This signal is sent through an antenna with a 433MHz RF Tx module (ANT.1).

Parts of the receiver Figure 3 shows a block diagram of the receiver part. The decoder and RF receiver module are powered by the power supply unit. The ANT.2 part of the receiver circuit gets the four-digit binary codes sent by the transmitter section.

Fig. 3: Block diagram of a receiver Here, the decoder is used to make sense of the signal that was received. The devices or appliances connected to the receiver section are switched on or off by the microcontroller in the transmitter section. Figure 4 shows a circuit diagram of the receiver part. It is made up of a transformer X2, a bridge rectifier BR2, a 5V voltage regulator 7805 (IC4), a decoder HT12D (IC5), a 433MHz RF receiver module (RX1), an antenna (ANT.2), a relay driver ULN2003 (IC6), a 12V voltage regulator 7812 (IC7), two 12V single-changeover relays (RL1 and RL2), and a few other In the receiver part, the data pins of RX1 are connected to pin 14 of the HT12D decoder (IC5). All of IC5's address pins are connected to ground, just like IC3's address pins are connected to ground. Two of IC5's output pins, D10 and D11, are connected to two of ULN 2003's input pins, IN1 (pin 1) and IN2 (pin 2). (IC6). The relays RL1 and RL2 are connected to the output pins 16 and 15 of IC6. There are two voltage regulators used here, one for the circuit (5V) and one for the relays (12V). The receiver section is easy to use. When the user presses the "light on" symbol on the touchscreen on the transmitter side, 1s and 0s are sent through ANT.1 and ANT.2 to the receiver. The 433MHz RF Rx module sends this information to the decoder IC5. The data is read by IC5 and sent

to IC6. Through IC6, the respective relays are turned on. The relays' contacts turn on the appliances. When the user presses the "light off" icon on the touchscreen, the D10 output of IC5 goes down. Pin 2 (IN2) of IC6 gets this low output, which makes pin 15 (OUT2) high. This turns off relay RL2, which turns off the bulb. The same is true for the fan. Fig. 4: Circuit diagram of the receiver Software The code is written in C for the AVR, and Atmel Studio 6.2 is used to compile it. STK500 is used to send the program to the microcontroller. At EFY Lab, the hex code was burned using a ProgISP programmer. Set the following fuse bits before you send the hex code (touchscreen.hex): set the following fuse bits: LOW = C1, HIGH = 99