240v fan speed temprature controler

[testlight]

Hi Forum

Ive always been interested in electronics. Enjoyed it at school, but unfortunately that was a long time ago and have forgotten just about everything.

There is a product i cant afford to buy, and I'm hoping i can make something similar for less, but need help with the circuit design.

https://www.growerssupply.com/farm/...01&productId=162278&pageId=ItemDetail&isDoc=N

My Fan is 240v AC around 160w

Can you help me with a circuit design. Or point me in the right direction so i can work most of it out myself?

Thanks loads in advance. I'm really excited about the idea of doing this project

 

[Nigel Goodwin]

What type of motor does your fan have? - that controller says it's "phase controlled", so presumably needs a fan with a universal motor?.

 

[testlight]

Hi Nigel,

Oh yes of course i should have thought to include more details about the fan. Updated fist post. Its about 155watt AC. Sorry not 100% sure what you mean by phase controlled. The fan is designed to run off regular main 240 volt

Here is a link to one on ebay

**broken link removed**


What are your thoughts on creating a circuit like this? Very difficult?

 

[Mithrandir2008]

TRIAC controlled AC voltage regulator is your best bet.

This circuit should work nicely.

https://www.circuitstoday.com/simple-lamp-dimmer-fan-regulator

Although I haven't used this exact circuit personally, I did use this kind circuit before and it works well for fans and bulbs. Anything more sensitive and you would need some sort of filter(which will be a bit large). I did notice that the regulator also had a temperature sensor so the circuit given won't be able to do that.

I'm sure there are may people here to help you with that.

 

[testlight]

Oh thanks. Your a champ Mithrandir

Yes i was speaking to the boys at jaycar electronics about a triac. They warned me they create some type of spike or something that could cause damage to fan motor, so a fliter might be a good idea too

So a triac with filter and maybe a thermistor?

Cheers

 

[Mithrandir2008]

Well here is the catch, if you want a thermistor based circuit the simple resistance circuit wont work.

The circuit basically operates on the capacitor C1 charging time. The change resistance in R1 varies the charge time and hence the magnitude of equivalent AC voltage. However, considering the application you want, the charge time must be temperature dependent.

And since thermistor resistance variations are non-linear, you can't simply replace the R1 with an appropriate thermistor value(i.e., temperature increases->resistance decreases->charge time decreases->voltage increases->fan speed increases). But then again maybe you could try for a linear resistance variation thermistor for your required range of temperatures.

I can't seem to think of any simple analog implementation to this circuit. Any implementations with PIC will be much more painful as you will need to bother about synchronization of gate pulses with the source voltage. Any others want to pitch in ideas?

 

[testlight]

Cheers again Mithrandir

yeah im lost on possible circuit design... this is how i kind imagine it working forgive the simpleness

Basically 2 pathways one that lets a limit flow of electrons/volts for idle control. The second activated by temperature that reduces resistance as temperature increases above setting.

View attachment 63513


Or

soon as temperature limit is hit fan goes to full power but a max speed is limited by variable resistor to limit 100% fan speed if desired

View attachment 63514

 

[Mithrandir2008]

Well the main problem is that the simple "adding electrons via parallel path" is more trouble than it's worth in AC designs. Even worse they would have to be current sources which involves large inductors and the design won't work that easily.

Also never introduce resistances in the main power line circuit. They are lossy and quite unnecessary now as they are being replaced with TRIAC's.

There is another slightly more complex circuit for TRIAC triggering. It involves a step down transformer, 741 comparators and integrators. I am still thinking if there is a simpler way to do this.

If anyone else is following this thread please pitch in.