Speed control of DC motor is very critical in most of the industrial systems where accuracy and protection are of essence. This paper presents the simulations of Proportional Integral Derivative Controller (PID) on a 16-bit PIC 24F series microcontroller for speed control of a DC motor in the presence of load torque. The PID gains have been tuned by Linear Quadratic Regulator (LQR) technique and then it is implemented on microcontroller using MPLAB and finally simulated for speed control of DC motor in Proteus Virtual System Modeling (VSM) software. Proteus has built in feature to add load torque to DC motor so simulation results have been presented in three cases speed of DC motor is controlled without load torque, with 25% load torque and with 50% load torque. In all three cases PID effectively controls the speed of DC motor with minimum steady state error.