# fan 220v ac speed control

Posted on Feb 4, 2014

if your AC fan have 3 button (like i have), button 1 (for low speed), button 2 (half speed), and button 3 (high speed), you can use Relay for switch the speed changing that button. But if your AC fan have 3 button (like i have), button 1 (for low speed), button 2 (half speed), and button 3 (high speed), you can use Relay for switch the speed

changing that button. I have built a circuit which works with Relays and my 2 bit instructions for 25%, 50% and 100% but it requires three relays and three AC Fan dimmers (ready made from market). I actually wanted to use Triac because relay logic is old and Relays burn easily and have a very small life as compared to Triac. in AC, the speed is proportional to amount of energy given to fan/bulb. which is again proportional to the area under the curve of AC voltage. e. g. here i shows a figure where three AC channels are switched at different times. you can see the AC wave delivered to the device is lesser than the original AC (Yellow curve). so the area under the AC curve is different in all cases and hence your o/p voltage varies. there is no PWM remember. Ajay i have seen your Home Automation software and how you use "lwidth" for generating PWM. I want to do similar thing but i need to generate 3 PWM as mentioned in my post above. AC Fan speed is control by a triac + diac + a VARIABLE Resistor that actually (with the help oa small cap) trigger the gate of Tric at various delay (according to the vale of variable RESISTOR) due to that delay tric get ON for that much time only. U break that variable resistor into= three fix resistor and switch them in to series with the help of transistor that will be control by your logic state. for example. if fan speed is controll fromm full to minimum by 500k resistor= use four 150k fix...

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