Can I use a zero to control a fan temp

[Drg]

I want to control a room that uses a 8inch fan around 100watt
Basicly I want day temp at 27 and night at 20, the fan I have they make these already but 80£ so thought if I can do it cheaper ?
Nothing fancy just temp control altering the fans power and 2 settings day and night

[scotty101]

Yes of course you could.

A DS18B20 temperature sensor works very well with the Pi
There are many AC relay modules that you can use to turn the fan on and off.
If you wish to control the speed of the fan then you'll need something more complicate.

[mutley]

As said above, Temp censor is easy. Control fan on/off is also easy.
But controlling a fan speed by changing the power delivered to the fan is difficult/expensive on the PI, you may be better off reading about PWM and looking at the Arduino.
But if the fan has a 2 speed switch (and not a potentiometer), and all you want is 2 speeds, then controlling that switch circuit through relay(s) that are in-turn controlled by the PI is easy. (just a bit of DIY soldering)
So it really depends on the fan you have in-mind and now it can be controlled / how you want to control it.

[Heater]

Do you mean just a fan?

Or a fan heater? Or some air conditioning system?

A fan on it's own cannot heat or cool a room. Not unless it is pumping hot or cold air in from somewhere else. Is it?

The best it can do on it's own is add heat to the room. The rate of 100 watts as you say.

[Drg]

the room is naturaly hot, the fan simly pulls air though which cools it, but nightime it cools down so fan needs to run slower,
nah the fan is 1 speed only, il show an example of whats curently about
http://www.ebay.co.uk/itm/SMS-Single-Th ... SwLVZVr4RP

[zealousd]

lol are we building a farm?

a Pi could do this no issues but i would not expose the board to excessive heat like near big lights

[texy]

The simplest solution is to have the pi switch on the fan when the room temperature gets above a certain temperature. You don't need to over complicate things by just lowering the fan speed - either just on or off. You could even have a different temperature threshold at different times of day if you want - its all down to the programming. The assumption is that the cooling solution you already have, ie the fan pulling in colder air into the room, is actually up to the job.

Texy

[Drg]

Well I need constant movement for negative pressure in the unit, stopping and starting would cause hotspot with no circulation and instable humidity,
And yeah you could say I'm doing a farm lol although not what your hoping I presume lol, that's unless your into hot chillies

Thanks all for replying btw, some come with controllers but a price too lol ,
https://www.google.co.uk/search?q=therm ... AQxqsQzQWM

There must be a way we can make this with pi?

[Heater]

Drg,

Chillies. Excellent.

My chilli seeds from the South Devon Chilli Farm refused to come up this year. Mind you this is Helsinki and it only just stopped snowing

Oddly, there is a chilli farm in Finland. Didn't have any luck with the seeds from them either last year. http://fataliiseeds.net

Luckily a few seeds I saved from last years crop have germinated.

What am I doing wrong?

[Drg]

Well I can say plant numbers I plant 200 expect 150 and then keep 30 to grow with
If your on about breeding, there self pollinating both male and female flower, here is humidity, which is why I need constant room movement, stops stale air and controls more even humidity, if your growing multiple strains then possible crosses will come,
I found with my breed they like good humidity but heat 26-28 day and 19-21 nights closer I get it the better results I have .

So does anyone know how these fans are doing it ? Lol

[texy]

If you get them to germinate and grow, you can try over-wintering them. Gives them a head start for the next season.
But if you have trouble getting them to germinate in the first place then you have a problem
I start from seed usually during the Christmas break in a heated propagator. But this year my enthusiasm has waned and I have so far only planted
a chillies worth of supermarket bought seed all planted in a pot. Lets see what happens

Texy

[texy]

So does anyone know how these fans are doing it ? Lol

If you ditch the commercial fan and use a standard 12V PC fan or fans, then you could use the pi with Pulse Width Modulation (PWM) to control the speed.
There is a number of threads on this, eg
viewtopic.php?t=79957&p=566480

You could also use the pi to measure humidity (both air and soil), temperature, light levels, etc also, if you felt the need.

Texy

[Drg]

Can't this be implemented on a bigger fan? I mean a PC fan won't shift 900m3 I'd need thousands lol

[Jednorozec]

You can use an Arduino to do AC phase control http://playground.arduino.cc/Main/ACPhaseControl and then connect the Arduino to the RPi via USB.