Building an arduino (or similar) based temperature control

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MisterCheif
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Building an arduino (or similar) based temperature control

Postby MisterCheif » Mon Dec 03, 2012 3:32 am UTC

So I'm at college now, and have discovered the problem that the thermostat in the room seems to be a cleverly disguised on/off switch. If it is set to above 60 degrees, it is on full blast, and if it's below, it is off. And now that it is so damn cold here, the heat is necessary, yet will also wake my roommate and I up in the middle of the night when it gets too hot. So I thought of something to do during my christmas break that could solve this.

I want to build and program an arduino (or something similar) robot with a temperature probe capable of toggling the dial across this point in response to temperature changes in the room. The problem is, I've never done something like this before, and I'm not sure what I need to get. I have a little programming experience, and I'm pretty sure I know the concepts necessary for this, I'm just not sure what I need to get, and where the best place to get it would be.

So far what I'm pretty sure I would need:

-arduino (or similar)
-servo/motor with enough torque to turn the dial, but a slow enough turn speed not to damage the servo or dial
-power supply (something I can plug into the wall would be optimal, as the thermostat is only about 4 feet from an outlet)
-temperature probe, and the necessary wires to allow it to be suspended from the ceiling about 1/3 of the way across the room from where the heater/window is.
-command strips (for attaching the motor/frame to the wall)
-potentially plastic or metal sheets, for fabricating the assembly that holds the motor/servo, and the connection between the motor and the dial.

What I have already
-potentially a soldering iron, depending on the board (check)

And, if anybody has any good resources for programming arduino (or an alternative) other than the just the documentation provided for it, or any suggestions for what else I might need, it would be much appreciated!
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Wnderer
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Re: Building an arduino (or similar) based temperature contr

Postby Wnderer » Mon Dec 03, 2012 4:20 pm UTC

My advice; buy a new thermostat or better yet contact the school facilities or whoever you're paying rent to and have them replace it.

EvanED
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Re: Building an arduino (or similar) based temperature contr

Postby EvanED » Mon Dec 03, 2012 4:41 pm UTC

Incidentally, "fancy on/off switch" is how almost all thermostats work. (Sometimes you'll see one that will control how open or closed a vent is, and will be more than off/on, but in my experience those have been the exception rather than the rule.)

It just sounds like yours has too wide a range or isn't working properly or something like that.

MisterCheif
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Re: Building an arduino (or similar) based temperature contr

Postby MisterCheif » Tue Dec 04, 2012 4:48 am UTC

This is in a school dorm, so buying a new one isn't much of an option. And based on the current responsiveness of Res Services to work orders, we'd be lucky to have it fixed by the end of the year, as our RA put in a work order for our curtains (which are somewhat broken) about 2 weeks before the first day of class in A term, which as somewhere around August 20th. They finally came to take a look at it the Monday before thanksgiving.

And our room is not the only one with the problem. If it is set above 60 degrees, the heater is on full blast whether the room is 30 or 90 degrees. If it is set below 60 degrees, the heater is off no matter the temperature of the room.

And mainly, I have no idea what to do during my month off between B and C term, so I might as well do something like this, seeing as I am majoring in robotics engineering.
I can haz people?
lulzfish wrote:Exactly. Playing God is a good, old-fashioned American tradition. And you wouldn't want to ruin tradition. Unless you hate America. And that would make you a Communist.

EvanED
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Re: Building an arduino (or similar) based temperature contr

Postby EvanED » Tue Dec 04, 2012 6:10 am UTC

MisterCheif wrote:And our room is not the only one with the problem. If it is set above 60 degrees, the heater is on full blast whether the room is 30 or 90 degrees. If it is set below 60 degrees, the heater is off no matter the temperature of the room.

Like I said, this is to be expected: it's typical of how a thermostat works...

Not to discourage you from hacking a bit though. :-)

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PhoenixEnigma
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Re: Building an arduino (or similar) based temperature contr

Postby PhoenixEnigma » Tue Dec 04, 2012 8:09 am UTC

EvanED wrote:
MisterCheif wrote:And our room is not the only one with the problem. If it is set above 60 degrees, the heater is on full blast whether the room is 30 or 90 degrees. If it is set below 60 degrees, the heater is off no matter the temperature of the room.

Like I said, this is to be expected: it's typical of how a thermostat works...

Not to discourage you from hacking a bit though. :-)

Either I'm misunderstanding, or that is not at all normal thermostat operation. A normal thermostat will turn on when the temperature passes some predefined point, and turn off again when the temperature goes back across that point. MisterCheif's thermostat, if I understand correctly, operates independent of the room temperature. If the dial is set above 60 degrees, the heater turns on and runs without stop, no matter what happens to the actual temperature. If it is set below 60 degrees, the heater never turns on. It's not a thermostat, it's just a plain on/off switch.
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EvanED
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Re: Building an arduino (or similar) based temperature contr

Postby EvanED » Tue Dec 04, 2012 4:55 pm UTC

Oh whoops... there goes my reading comprehension. :-) Yes, you're correct. (Reading not very carefully, it sounded like MisterCheif was under the mistaken but common belief that thermostats will increase the amount of heat coming out the further away from the setpoint the real temperature is, and so if you want a room to heat faster you can turn the thermostat up further.)

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Wnderer
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Re: Building an arduino (or similar) based temperature contr

Postby Wnderer » Tue Dec 04, 2012 9:52 pm UTC

Well if you are really set on doing this.

You need a motor like one of these.
http://www.goldmine-elec-products.com/p ... ber=G16468

You drive the motor with an H-Bridge like one of these.
http://www.ti.com/lit/ds/snvs092c/snvs092c.pdf

And you use a 10k thermistor like one of these.
http://www.digikey.com/scripts/dksearch ... 67&stock=1

This appnote tells you to how to select a linearizing resistor.
http://www.analog.com/static/imported-f ... apter7.pdf

The goldmine motor has an optical sensor but if that doesn't work you can use this kind of photo interrupters to stop the motor.
http://www.digikey.com/product-search/e ... l%20sensor

Jeff_UK
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Re: Building an arduino (or similar) based temperature contr

Postby Jeff_UK » Sun Dec 09, 2012 7:02 pm UTC

I had a thermostat which had a light inside it that generated enough heat to almost instantly turn itself off as whenever it activated .. if the stat was set to less than 22 C . Not exactly the pinnacle of engineering excellence.

Not to discourage hacking for the sake of it ... but have you tried searching for the manufacturer of the stat on google, you might be able to procure a replacement and install that yourself....


The simplest solution would probably be to access the electrical circuit directly and either replace, or bypass the existing temperature sensor, using a microprocessor in place of a bi-metallic switch is a tad overkill. That does open yourself up to certain questions around electrical safety, which you bypass by using a motor.. so have fun :D
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