I am going to add a temp-controlled fan assembly to my home theatre cabinet. From my googling I believe I understand how I would have to use a MOSFET for this, but all the examples have an additional 12V power supply. How would I go about using a single power supply to power both the arduino and two 12V fans? Is it as simple as taking a 12V power supply and simply attaching it to both (since it appears the arduino has a regulator capable of handling this voltage)? If so, would this end up generating an excessive amount of heat/waste energy?
Yes, you can run both fans and the Arduino off one power supply. I would add some 1,000uF @25V capacitors across the fans just to kill some of the ripple the fans will produce. You can buy a 12V @2A switching power supply from Jameco or e-bay.
Are you simply wanting to turn the fans on and off or control speed? Controlling speed is more elegant and you can use the PWM capability of the Arduino to accomplish this. You might just use a transistor in "sink" mode instead of the MOS-FET especially if your Arduino is one of the 3.3V models. Finding a MOS-FET with a 2.5V Gate Threshold might be tough. A regular NPN transistor will saturate at >0.7V which makes it easier.
I am going to add a temp-controlled fan assembly to my home theatre cabinet. From my googling I believe I understand how I would have to use a MOSFET for this, but all the examples have an additional 12V power supply. How would I go about using a single power supply to power both the arduino and two 12V fans? Is it as simple as taking a 12V power supply and simply attaching it to both (since it appears the arduino has a regulator capable of handling this voltage)? If so, would this end up generating an excessive amount of heat/waste energy?
Thanks!
The easiest way to do this is to get a Relay board from EBAY - there are plenty of Arduino compatible boards such as
As a NOOB this is the simplest (and almost the cheapest !) way of putting together controllers for higher voltage appliances.
Note these are on/off relays only - i would start there and then if you want to get fancy with PWM speed control later you can look at a MOSFET based solution
If you want a packaged and "done" solution, I have used this little board to run a motor. It wouldn't care it's a DC fan and you can either turn it full on or PWM. You can even control both fans independently since this board has two L298 H-Bridge devices. If these are brushless fans, don't ever go "reverse". $39.90 and you are done!
rmetzner49:
If you want a packaged and "done" solution, I have used this little board to run a motor. It wouldn't care it's a DC fan and you can either turn it full on or PWM. You can even control both fans independently since this board has two L298 H-Bridge devices. If these are brushless fans, don't ever go "reverse". $39.90 and you are done!
Wow that is a pretty cool all in one solution for this application - i assume there is a seperate Vin for the motors so they can be driven without overloading the onboard Vreg ?
Yes, there are separate connectors for each. On that bank of three Phoenix terminals, two are for motors and one is the motor supply. The one alone is for the nominal 7-20V input which also powers the "servo" bus. The .1" male pin headers are organized like an RC_Servo connection. Also cool is it uses the Leonardo template to program it since it's a 32u4 processor. -- Rob
jackwp:
I would use the arduino, and a relay board with 2 relays. Not as expensive, and more "arduino".
How are you going to decide when to turn the fans on?
Yep good point
OP - throw in a Dallas DS18B20 when you are cruising EBAY and you are done - you can get them in Stainless waterproof (supposedly) housings on ebay for around $2
A 1 amp 12 volt supply should work well. 200ma X 2 = 400ma, then arduino 50ma. You have not got up to a half an amp there yet. Arduino Vin can be 12 Volts (or a bit more), but the onboard 5 volt regulator starts heating up a bit at 12 volts. If you have a couple diodes, put 2 or 3 in series to drop the 12 volts a bit going onto the arduino board, for a cooler arduino regulator. Probably not necessary, but easy if you have the diodes.
I added a PC case fan to my Home Theater and simply turned it on with a bi-metal, non-adjustable thermostat set to come on at 100F. It's attached on top of the receiver's vents. It would be nice to be able to slow it down since it's sort of noisy. I'm even running a 12V fan off a 9V wall adapter. If all you want to do is turn on the fans and no other control, you don't even need the Arduino. Just wire directly to the thermostat. --Rob
Not to be picky, but looks like that Thermostat turns on at 113F. But that is an interesting link. Maybe I can find some of different values. -- Yea, I just looked, and that company has many different values.
I'm completely aware of the conversion factor from Celsius to Fahrenheit and I bought mine at Grainger down the street from me and it WAS spec'd at 100F. Not that 13 measly degrees means a rat's ass anyway.
Don't get offended. You were of by only 13%. Normally nothing to be worried about, but sometimes it could be.
There are lots of people reading this forum, and we should try to give them somewhat accurate info.
BTW, I would think 13% would be really a great number if I got it on my CD. LOL
You provided a good link. There must be many uses for those thermostats, I will probable get one or two, when I decide what temp I want.