i am planning on getting started with an arduino project. it's just been a few days since i found out that the arduino is so much more than just the little robot i used to play around with during artificial intelligence lectures at university :) .. so here i am with my first project to be realised with an arduino:
about a year ago i have converted our test facility's cooling so that it can now use free cooling. the trick was very simple. i've installed two huge fans with filters that suck cold air from outside into the room and two identical fans which blow hot air that is collected in a containment inside the room back outside again. Like this we could lower the power consumption for cooling our test facility dramatically (from several thousand watts per hour powering all the Air Conditioning Units we had installed down to about 600W peak per hour powering the fans.. plus we need one set of filters every month :) ). So far i have a fan speed regulator (more details later) that is controlled by a simple potentiometer. since there are usually some people in the test room during the day we just adjust the fan speed to the current cooling demands we have. the problem comes during week-ends or now in the winter when we have cold nights and nobody is around to either turn the fan speed down or up.
that's where the arduino comes into play: i would love to be able to control the fan speed through an arduino with one or more temperature sensors connected to it. the problem is: i am more of a software engineer than a hardware guy and i know only very little about electronics.
i have googled around and found some solutions which might work but i am missing all the details to put it all together.
so here is what i have:
- 4 HELIOS HRFW 400/4 TK Fans (230V Single Phase AC Motor) The Motor can turn in either direction depending on which terminals i connect the power to.
- A Fan-Speed controller (triac based). here is a link to the german and english datasheet (second page is english): Data Sheet
- a potentiometer 470kOhms as recommended by the datasheet.
now i found one solution which looks simple enough for me to reproduce: a Photo-Resistor Cell instead of the Potentiometer which is hot-glued to a white led (and wrapped into black tape or something else). the LED is then controlled by a PWM output of the arduino. some guy did a youtube movie about that: http://www.youtube.com/watch?v=7yEABsNyRfo Here are my challenges with that solution: - which photo resistor should i take.. looking at how the pot is attached to the triac it seems that it needs to deal with 230V .. so maybe this one here from farnell would that be okay? - how do i attach it to the triac? the potentiometer is connected with the first two feet to the power source and the third pin is connected to a cable from that fan-speed controller.. can i simlply put the photo resistor between the power source and fan-speed controller cable or do i need to solder in a resistor in parallel with it?
the second solution i found was to use a digital potentiometer to control the fan speed controller.. i found here in the forum some links to such parts but they where all not ment to work with 230V on the potentiometer side. the i2c version i looked at could only use the same voltage on the three potentiometer-output-pins as it was powered with from the arduino.. so 5v in that case.. is there a way i can "boost" that ? this seems to clearly be the nicer and more accurate solution but i am afraid it already requires alot more knowledge than what i currently have.
can anybody help me getting that project going? is there maybe already a finished box out there which accepts pwm input from the arduino and regulates the fan speed accordingly? that would also be a solution, i am not in any way bound to keeping on using the triac that i am using right now.. it was just cheap and it perfectly does the job at the moment :)