Arduino AC phase control, diagram help

Hello and thankyou for your time,

I have a air handling system in my house a 150mm or 6" inline fan with the following specs.

• Phase: 1 ~
• Input power (P1): 109W
• Current: 0.48 A
• R.p.m.: 2527
• Capacitor: 3 µF

And i really want to control the fan from my arduino using some sensors like a light and temp sensor
, I understand the principle about the wave forms and timing with zero point detection but i dont have the electrical knowledge to design such a pcb or code it. But luckily Arduino have a official post on AC phase control however i need some help with the electronics as the link to buy the pcb no longer works i must build it myself, i have done loads of soldering and messed about with loads of sensors and other things, and ALSO i have done domestic and commercial electrics for years as my bro is a fully qualified electrician so AC is no issue but when i comes to electronics i know very few symbols but i do have a poster with most of them to refer too, but that is still not enough to understand the wiring diagram fully, i have noted what i think each component is but the AC outputs some what confuse me as do the grounds and attached the image below and a online link.

in black text is what i added, can some one please tell me where i should attach the 3 GND,s and why there is two neutrals, what line is and Heater within the wiring diagram. And from what i read from the linked arduino page i should place a 10k ohm resistor on the pin 5 of the H11AA1 ?

And lastly what is the sketch actually doing from what i assume in the loop function “i” is the value that varies the voltage output ? and its dimming a heater ?

Sorry to be so stupid, i pray some one can help me with this. And thank you for your time.

From edd

Your motor sounds like an ordinary single-phase squirrel cage.

You can turn it on and off with eg a relay, but you cannot change it's speed (much) by phase control of ac mains.

For that you need a variable frequency power source - much more difficult.


Thank you, hmm that sucks. My friend owns a small development company and they used a massive group of resistors and switches and cut of the leading and trailing edges of the waveform with zero point detection, but yes you’re right the minimum speed was like 41% and it would start to knock, i was hoping to one up him and find a better way but looking at your experience i will stop the hunt for a better solution.

However this Variation in power source frequency is it really really hard, and could i find a tutorial on it ?
Sound like i would be making a variable digital ballast which i have seen in the past but never designed or constructed let alone coded.

There's a bit more to it than just variable frequency - you have to limit the current at low frequencies to avoid burning out the motor. And it's torque at low speeds will be much less than nominal..

If you fitted a dc motor it wold be totally and easily speed controllable.

One from a car electric engine cooling fan would be about the right size....though it's maximum rpm may not reach 2500

Or a heater circulation fan

You can pick these up cheaply from scrapyards if you want to experiment.

And you'd need a 12-14v supply of eg 15A capability


For easy speed control you want either a DC motor (easiest) or multiphase AC (typically 3-phase) which
can be controlled (speed and direction) with an off-the-shelf V/f inverter drive. Note that brushed DC
motors aren't the best choice here as brushes wear out, a BLDC would be more suitable, and they are
somewhat more involved to control.

That 106W induction motor can probably be replaced with 50W or less DC fan, BTW, they are that