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Showing posts from January, 2010

Experiment No. 10: Use of UART Library to Communicate with PC

MikroC has two sets of built-in library functions for UART communications: Software UART and Hardware UART. Since PIC16F628A has a built-in hardware USART module, we are going to use the Hardware UART library. Some PICs don't have hardware USART, such as PIC16F84A. In such cases, any digital I/O pins of PIC can be used for Asynchronous Serial Data Transfer using mikroC Software UART libraries.

Experimental Setup

The UART Rx and Tx pins in PIC16F628A are multiplexed with RB1 and RB2 pins. In this experiment, we are just sending some character data from PIC to a PC as demonstration of the technique. On PC, the HyperTerminal program should be running to receive data from the PIC16F628A. Since our PIC board does not have a TTL to RS232 voltage level shifter, we are going to construct it on a breadboard. Here is my Level Shifter Circuit:



Experiment No. 9: DC Motor Speed Control using PWM

This is an extension of Experiment No. 8 (Click Here). The PWM output is here connected to power a DC motor through a NPN driving transistor. The motor driving circuit is built in a breadboard, as shown below. The circuit is pretty straight forward, the PWM output from PIC pin drives the BC547 transistor ON and OFF, and the current to drive the motor is provided by the collector current in the transistor. The diode is for back EMF protection. I am using a small 6V DC motor from an old cassette player. For motors that require more current to drive, a darlington transistor pair or high power transistor is recommended.