Controlling speed of AC motor is required in industries as well as in domestic use. In industries the required motion control is achieved by controlling speed of big and heavy AC motors. They use variable frequency drives (VFD) for speed control. In some other applications like fan, blowers, heaters etc another method for speed control is used that is phase angle control. By varying phase angle, the current supplied to motor can be varied. And by varying supplied current the speed of motor can be varied.In domestic application the phase angle control method is used. The best example is fan regulator. In domestic fan regulator DIAC and TRIAC are used to vary phase angle of fan motor. This is very easiest method to vary AC motor speed.
Here is a very simple example of AC motor speed control given by changing firing angle of TRIAC with the help of micro controller 89C2051. Varying speed of AC motor by means of changing firing angle of any thyristor is very widely used method. One very nice example is fan regulator in which a fan…
Obviously you might have seen so many temperature controller and indicator applications using different micro-controllers, micro-processors or other controlling devices. But this is the actual application of temperature controller that controls speed of DC fan as temperature varies. It is not a simple ON-OFF type controller that switches fan ON / OFF when temperature increases / decreases certain limit. But its continuous type controller that continuously varies speed of DC fan as temperature increases / decreases. That is a demo of actual industrial application.
Here in this application, I will show you how we can control the speed of single phase 230V AC motor wirelessly using IC555. Along with IC555 I am using zero cross detector (ZCD) circuit to trigger the monostable and an optocoupler to trigger thyristor. Let us first see the block diagram of the AC Motor Speed Control System.