UNDERSTAND BASIC CIRCUIT FOR THE COMPONENTS

WEEK 21

Last week, i had purchase all the components needed in developing the circuit, for this week before assemble all the components,  the task for this week is to find the  basic circuit .In developing the hardware part,  the connection in the hardware part is not same as the proteous connection because the hardware connection is assemble by following the datasheet.

PIN DIAGRAM FOR PIC

OSC1 and OSC2 pins of the PIC must be  connected to 20MHz crystal to execute every single program line in the system. 20MHz crystal is used because this is the maximum frequency that the PIC can support. If over frequency the PIC will burn. Else if crystal speed less than 20MHz then PIC response speed will slower. The MCLR pin of the PIC is pull up to 5V through a 10KR resistor.

The PIC can operate using 4.5V to 6.0V DC voltage. In the project is operating at 5.0V (by using 7805). It is DIP layout (dual in line package) and suitable for project. It has 40 pins but only 33 I/O pins can be set as digital input or digital output. The digital output of the PIC is 5V (for signal 1) and 0V (for signal 0) these signals will be directly connected to actuators for control purpose.

 When the PIC pin is set as digital input. It will detect input voltage 5V as signal 1 and 0V as signal 0. Any voltage less than 0V or more than 5V will damage PIC.

VOLTAGE REGULATOR CIRCUIT

The voltage regulator module is used to protect PIC and other connected sensors / actuators from over voltage. This is because PIC and all other connected sensors, actuators all support 5V DC only. Over voltage will cause any of the module burn. LM7805 is used to regulate voltage in the system and output 5V DC (max output current: 1000mA). It supports input voltage from 7V DC to 18V DC. If the input voltage is over, the LM7805 will burn or auto shutdown due to overheat. The generated 5V from LM7805 will be noise filtered by 0.1uF ceramic capacitor and a 1000uF electrolytic capacitor. This is to avoid high frequency oscillation on the outputs which may cause system hang or unstable. A diode is connected at the input of the LM7805. This is to avoid voltage connected reversely. An on/off switch is used to turn on/off the system and a LED (5V, 5mA) is used to indicate the system is power on/off. The LED is connected through 1KR resistor to limit current pass through LED is 5mA.

LCD PIN DIAGRAM

The backlight power rail differs often, the polarity can be different and some screens need an external resistor. Usually the supply voltage is 5V DC. Character LCDs can operate in 4-bit or 8-bit mode. In 4 bit mode, pins 7 through 10 are unused and the entire byte is sent to the screen using pins 11 through 14 by sending 4-bits (nibble) at a time.

PUSH BUTTON CIRCUIT

BUZZER CIRCUIT

MOTOR DRIVER CIRCUIT

The IC is also referred to as a push-pull four channel driver. An h-bridge is ideal for driving motors. The L293D provides two h-bridges for driving both motors on the robot base. The motor direction is controlled by logic signals from the microcontroller. Two signals per motor are required to control the direction and the below showb the pin diagram for motor driver connection .