PC-Based DC Motor Speed Controller

Here is PC based project to control DC motor speed , which can have various uses in real life situations.
Circuit diagram of pc based DC motor speed controller

Circuit Description
As this project is control through computer so it utilizes both hardware as well as software. The hardware used here is to interface the motor and computer. The interface circuit or hardware comprise a decoder IC (IC1), hex inverter IC (IC2 and IC3), resistor network and Timer IC (IC4) with motor driver transistor T1.
IC1 accept the binary code from the computer through parallel port which further decoded and converted in low output. The eight low output labeled as Q0 through Q7 which is further given to the input of hex inverter IC (IC1 and IC2). The out from there inverter IC is high because it invert low input to high output.
The output of inverter IC is connected to resistor network made from VR1 through VR8. The resistor network VR1 through VR8 is connected to diode D1 through D8 respectively as shown in circuit diagram and further given to input of timer IC. The resistor R1 and R2 and capacitor C1 are timing component of astable mode configured by IC4. The square wave output from IC4 is given to base of motor driver transistor T1 through resistor R3, which further drive the motor according to binary output from computer.
The software of the project is written in high level language (C programming language) in order to overcome the problem like complex and tired work.
Resistors (all ¼-watt, ± 5% Carbon unless stated otherwise)
R1 = 82 KΩ
R2 = 56 KΩ
R3 = 1 KΩ
VR1 – VR8 = 470 KΩ
C1, C2 = 0.01 µF
IC1 = 74LS138
IC2, IC3 = 74LS04
IC5 = NE555
T1 = SL100 with heat sink
D1 – D8 = 1N4148
M1 = DC motor 5V
25 PIN ’D’ type parallel port

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