10-06-2017, 06:50 AM
Abstract: - In most of the industrial processes it is required to rotate DC (or AC) motor forward and reverse for desired time. First motor rotates forward (clockwise) for some time (say 2 3 min) then it stops for some time. Again it rotates reverse (anticlockwise) for some time and rests. This process repeats every time when gets triggered.
For example, in automated bottle filling plant, the bottles are moving on conveyor belt. When it comes under filler, the filler comes down (that means motor attached with mechanism rotates forward) then it fills the bottle (that means motor stops). Again it goes up (motor rotates reverse) and stops. As the next bottle arrives, the same process is triggered again. For moving filler up and down the time of rotating motor forward and reverse is calibrated and fixed. Also the motor stop time is calibrated based on time required to fill the bottle. Another very good domestic application is washing machine. Once timer is set to wash cloths the motor automatically rotates forward and reverse for fixed time (10 15 sec) with small pause in between. So I can give thousands of such applications where there is a need to run motor forward stop reverse forward . and so on.
Now because this is sequential process we can use sequential timer. Sequential timer is widely used circuit in industries because in most of the industries all the processes are of chain reaction type. That means one process ends and it triggers next. The last process triggers first process when it ends. And thus the cycle continues. These sequence timers are micro controller based multi-functional and programmable. But here I have developed a sequential timer using simple IC555. So let us see how it is done
Here the process is of three steps (forward-stop-reverse), I have used three stages of IC555 connected in cascaded to form 3-stage sequential timer.
1st stage rotates motor forward
2nd stage stops motor
3rd stage rotates motor reverse
These stages actually energize or de-energize relays that connect motor with the supply. Let us see the block diagram of this sequential timer controlled DC motor.