My First Arduino Project: Autonomous Solar Heat Controller

Greetings Ardy forum!

I've just completed my 14 step lesson booklet and I'm anxious to start my first project. I want to create a simple thermostat that draws heat into the house from a passive solar heater (Ex: HOW I MADE A SOLAR POP CAN FURNACE / HEATER - YouTube).

The theory behind my project is to have the Solar heater only heat the house if the solar heater is warmer than the air inside the house and only if the house is colder than a desired temperature. I figure for a challenge I should put some kind of LCD display and some controls to change desired temperature.

I figure I will accomplish the project by using two temperature sensors connected via long range wires. I'm hoping to use something simple such as RJ11 cable. I will use one temperature sensors to detect the temperature of the Solar heater, and the second one to sense the temperature inside the house. I will use the Arduino and some simple logic to determine whether or not we should heat the house. When it's decided that the Arduino should heat the house, I want to active a relay which turns on a 15amp 120volt house outlet, which will have some kind of high powered fan plugged into it, which will be connected with some piping into the solar heater.

My first questions regarding the project are:

1.) What temperature sensors do I want to use for this? My Arduino Starter kit actually came with a TMP36 Temp Sensor. Can I just get another one these? Are they common? Cheap and easily available? Fairly robust? Also, how would I go about connected the TMP36 to some RJ11 Cable? Any ideas?

2.) The relay that came with my starter kit is model number JZC-11F. I believe it requires 5v DC to activate it, but I'm unsure of whether or not it could handle 15amps AC. I somehow doubt it. It's pretty small. Can you guys suggest a relay that will work well with the Arduino that can relay 15amp AC?

3.) Not sure how to use LCD screens with an Arduino, or how to build menu's etc. So any links in the direction would be great!

Thanks for reading! I'm totally loving the Arduino.

Interesting project. Any idea how many KW you are going to get out of it?

I doubt if your fan draws 15A at 120V, that would make it 1.8KW which I am guessing would be a great deal more power than you are getting from your solar module. Its probably more like 200W or less (PLEASE CHECK - DON'T TAKE MY WORD FOR IT), which means that your relay would need to handle 2 Amps at 120V. Which it might well do!

The temperature sensor is digital and should therefore work ok on the end of a reasonably long wire. I assume the CAT5 cable is not connected to a local network, but just for the sensor - in which case, you can connect the three leads of the sensor as you like.

Si:
Interesting project. Any idea how many KW you are going to get out of it?

I doubt if your fan draws 15A at 120V, that would make it 1.8KW which I am guessing would be a great deal more power than you are getting from your solar module. Its probably more like 200W or less (PLEASE CHECK - DON'T TAKE MY WORD FOR IT), which means that your relay would need to handle 2 Amps at 120V. Which it might well do!

The temperature sensor is digital and should therefore work ok on the end of a reasonably long wire. I assume the CAT5 cable is not connected to a local network, but just for the sensor - in which case, you can connect the three leads of the sensor as you like.

The Solar Heater actually doesn't generate electricity, but instead absorbs heat. The fan is powered from the house grid (which may be powered by wind eventually). The fan will just be a regular 3 prong (live, common, ground) plug. The reason I suggested a relay that could handle 120v/15amp is so I have a bit of playing room if I want to scale this thing up to someday power an 1800w fan (I may use this to heat a workshop or a green house someday).

And the RJ11/45 cable is simply used as a cheap inexpensive way to run wires that are shielded from the elements. I was also considering the headphone jack/plug style of cable as well. It will not be connected into a network of any sort.

Thank you for replying.

The Solar Heater actually doesn't generate electricity

Hi, I meant KW of heat not electricity.

Now, if you could make PV cells out of coke cans, you would be a very very rich man!

The network cables are a good idea. I would imagine that you would get a good long range on them fro the temp sensors.

I was just a bit concerned that you were going to use more energy than you were capturing from the sun. Because if so, you may as well just power an electric fire from the mains.

Si.

Si:

The Solar Heater actually doesn't generate electricity

Hi, I meant KW of heat not electricity.

Now, if you could make PV cells out of coke cans, you would be a very very rich man!

The network cables are a good idea. I would imagine that you would get a good long range on them fro the temp sensors.

I was just a bit concerned that you were going to use more energy than you were capturing from the sun. Because if so, you may as well just power an electric fire from the mains.

Si.

Ahh of course. Depends on the sun light exposure. I may do up a solar tracking unit with this thing as well. We will see. But in bright sun light even in mid winter, there is nearly 1Kw of heat energy per square meter. So If i Make this thing 3m x 1m (that's a lot of pop cans) That's a lot of passive heat :smiley:

I'm also looking into use this kind of system to heat water up, and then at night time pull the heat from the water to heat the home. I figure some kind of big truck radiator might do the trick.

Thats pretty efficient!

I think I am going to have to have a play with this. Although I suspect it may not work quite as well in cloudy north west England!

There have been some postings here on solar tracking - search for heliostat.

Good luck with it.

Si:
Thats pretty efficient!

I think I am going to have to have a play with this. Although I suspect it may not work quite as well in cloudy north west England!

There have been some postings here on solar tracking - search for heliostat.

Good luck with it.

Thanks man! I've got some tweaks I want to do with the current design people are using. I think it may severely increase the available surface area!

http://canada.newark.com/tyco-electronics-potter-brumfield/t9as1d12-5/power-relay-spst-no-5vdc-30a-pc/dp/26M8314 Would the Arduino be able to use this to switch 120v power?

Hi,

It would, but you could not drive it directly from an Arduino pin, it would draw too much current. You would have to use a transistor.

You could use a relay shield like this: http://www.robotshop.com/seeedstudio-arduino-relay-shield.html

The relays will cope with 5A at 240V so probably more at 120V. Even if 5A at 120V, that would let you switch 600W.

Si:
Hi,

It would, but you could not drive it directly from an Arduino pin, it would draw too much current. You would have to use a transistor.

You could use a relay shield like this: http://www.robotshop.com/seeedstudio-arduino-relay-shield.html

The relays will cope with 5A at 240V so probably more at 120V. Even if 5A at 120V, that would let you switch 600W.

I'm just starting to realize just how versatile this little microcomputer really is. How would I write code to control a shield like that? Is it similar to controlling a Shift Register Chip? Using 3 pins to control many?

Is it similar to controlling a Shift Register Chip?

Much easier than that. You just set pins to be on / off using:

digitalWrite(pin, HIGH);
digitalWrite(pin, LOW);

Each relay will have its own pin. Unused Arduino pins can be used by your other parts.

Si:

Is it similar to controlling a Shift Register Chip?

Much easier than that. You just set pins to be on / off using:

digitalWrite(pin, HIGH);

digitalWrite(pin, LOW);




Each relay will have its own pin. Unused Arduino pins can be used by your other parts.

Snoof! I'm still unsure of how that Shift Register works. Thanks for replying man.

When controlling line voltage my first recommendation is X10. It allows you to be code-compliant with minimal programming or expense.