I have a project on my hand and what I have to do is to keep the temperature of inside of a box at a certain temperature level.
My box has a dimensions of 60x60x60 and let's say I have to keep the temp. at 30 degree. When the temp is high I'm gonna use 2 fan and fresh air will enter to the box. When temp gets cold, I have to give some heat inside but question appears at this point... What kind of material should I use?
Ideas so far are
Peltier: Practically have many disadvantegous. Ice blocks appears on the cold side of peltier. So this means they are going to melt down at some point. Also peltier draws too much current. I'm open to new ideas about peltier.
Terrarium bulbs: Some people use bulbs on their terrariums to increase the temperature. Is it wise to use them with arduino? Second concern of mein is if they give too much heat or not? I dont want sudden temp peaks.(I'm gonna have also temp sensors) I'm also fully open to new ideas about these bulbs.
Main purpose is to stabilize oxygen level inside of the box with an gas pump and oxygen sensor(any recommendations except Figaro KE-25 that's the one I've already knew). Before going further on oxygen I need to handle with temperature.
I need your ideas and advices on my project.
Cheers
A Peltier element is a heat pump, not a heating element, it does generate some heat, of course, but it mostly transfers it from the cold side to the hot side.
The easiest way to generate heat is to use a couple of high-wattage resistors.
P = V²/ R, for example, a 10Ω resistor @5V will generate 2.5 Watts of heat.
Hard to say without more detail. There are obviously many ways of doing this, which makes most sense is not clear. How well insulated is this box going to be? How stable do you need the temperature to be? What are you using the box for?
I'd go with the terrarium lights solution as a first try. You could use several low wattage bulbs to give you more control than just on or off. You could put them under the box so that heating wouldn't be so abrupt as having them inside. Arduino can control them via relays.
erondem:
My box has a dimensions of 60x60x60 and let's say I have to keep the temp. at 30 degree.
What units?
Degree = Celcius I would guess. Could be Fahrenheit but then you'd be cooling in most climates.
That 60x60x60, is that mm, cm, feet, meters, inches, or something else? Makes a big difference in how to heat the box - ranging from Peltier elements to big gas burners.
PieterP:
A Peltier element is a heat pump, not a heating element, it does generate some heat, of course, but it mostly transfers it from the cold side to the hot side.
The easiest way to generate heat is to use a couple of high-wattage resistors.
P = V²/ R, for example, a 10Ω resistor @5V will generate 2.5 Watts of heat.
Pieter
Do you have any Idea how can I calculate if they are enough or not? I did some math and thermodynamics but I think I'm lost.
wildbill:
Hard to say without more detail. There are obviously many ways of doing this, which makes most sense is not clear. How well insulated is this box going to be? How stable do you need the temperature to be? What are you using the box for?
I'd go with the terrarium lights solution as a first try. You could use several low wattage bulbs to give you more control than just on or off. You could put them under the box so that heating wouldn't be so abrupt as having them inside. Arduino can control them via relays.
Box is not going to be well insulated. It's a thin material(I dont know what is its name but lets say weak insulated.) It is going to be an animal care unit. The temperature inside must be stabile at lets say 25 degree(It is going to be changable afterwards). Since unit will be used indoor, the temp difference wont be huge.
wvmarle:
What units?
Degree = Celcius I would guess. Could be Fahrenheit but then you'd be cooling in most climates.
That 60x60x60, is that mm, cm, feet, meters, inches, or something else? Makes a big difference in how to heat the box - ranging from Peltier elements to big gas burners.
Good point sorry I missed that one. They are in cm. The aim is more than heating a cold box but stabilize the temp inside. I would guess temp difference won't be larger than 5 Celcius .
Since unit will be used indoor, the temp difference wont be huge.
I think the possible temperature difference between the room and the inside of the box and the thermal insulation of the box will both be critical factors.
For example if you want to keep the inside of the box at 25C but the room temperature is 30C then fans will not cool the box since the air will be at 30C.
As another example lets assume the room temperature is 25C and you want the box interior to be 30C but the box is highly conductive of heat. You would apply heating inside the box but because the box quickly conducts the heat away you would effectively be trying to heat the room.
Terrarium lights might be a way of delivering heat but I would guess they would mainly come on at night when it is cooler so would the light affect the animals?
At such a box size, poor insulation and temperature difference requirement I guess you'll be looking at heating elements in the tune of 50-100W. Some experimenting will be needed.
It also depends on the animal you have in your box. I recall geckoes prefer to have a heated stone to bask on (the stone should be 30-33° or so, you don't want to cook your pet), others prefer a heat lamp to bask under. You best ask your local pet store or a specialised forum about this.
A small fan may be needed to properly distribute the heat through the box, especially if you heat from above. When heating from below, you have to be very careful not to create hot spots - again to prevent cooking your pet.
In case of a basking lamp, you're supposed to keep it on for 8-12 hours a day, giving your pet a place to bask. This may actually overheat your box, in which case you may have to look into cooling (exhaust fan) rather than heating.
ardly:
Terrarium lights might be a way of delivering heat but I would guess they would mainly come on at night when it is cooler so would the light affect the animals?
Not necessarily - my terrapin has a heat "lamp": looks like a lamp, screws in a regular light socket, but it radiates no light, only heat.
erondem:
Do you have any Idea how can I calculate if they are enough or not? I did some math and thermodynamics but I think I'm lost.
Trial and error.
If the box were perfectly insulated, you could use the molar heat capacity of air to calculate how fast the temperature will rise.
Q = Cp·n·ΔT
(P = Q/Δt)
P / (Cp·n) = ΔT/Δt
ΔT/Δt is the rate of temperature change in degrees per second.
You can estimate n by using the ideal gas law at room temperature and atmospheric pressure, because the temperature difference is relatively small.
n = p·V / (R·T)
(p = 105 Pa, V = (0.6m)³, R = 8.31 J K-1 mol-1, T = 300K)
However, that doesn't tell you anything, because theres a huge amount of heat that is lost to the environment. It makes a huge difference if you use a plastic box with some holes in it, or a completely isolated container with minimal heat losses. The temperature of the environment also plays a huge role. (The transferred heat through the walls of the box is proportional to the temperature difference between the inside and the outside.)
Is this some kind of laboratory setup?
What type of animal is it and how many will be in the box, I don't think we have been told that have we?
Is there only one box or will there be a roomful of them?
My inclination, particularly if there are are multiple boxes, would be to put the box in an air conditioned room.
The box system could then fine tune the temperature but I would definitely have some thermal insulation otherwise you will be trying to heat/cool the world.
You will want to consider the fail-safe situation, if something fails is it better for the animal to be too hot or too cold.
Here is a site that works out heat loss from buildings which is essentially the problem you are looking at.
It has an Online heat Loss Calculator which is good as it will let you play with numbers and see how things work.
Remember in your case unless you are certain the room temperature will always be lower than the box temperature you might need to consider heat gain (presumably the calculations can be reversed or perhaps the equations already cater for when the outside temperature is greater than the internal temperature).