Hope you are doing well. I am completely new to Arduino. However, I have started to learn implementing with the projects. Now, I have a project in hand. Although, not sure if I can get it done with Arduino. So, I want your valuable advice.
Project: I want to have a polycarbonate box ( 7 x 7 x 7 inches, I am open to increase the box sizes to 20 x 20x 20) that will work as something like controlled climate chamber. I want to control the humidity and temperature inside the box, for example, I want to maintain 10C and 40% Relative Humidity in the box. I think I need to have small sized heater, cooler, AM2302, relay, PID, humidifier and dehumidifier for the box. I found the components but I am not sure if I can control that with arduino. Could you please share your knowledge about the project on how I can proceed with the project and what components should I use for the project?
Working Temperature Range : 5C-45C
Working RH Range : 20%-100%
I did find several resources to increase temperature and humidity when it is required to increase more from the ambient. However, I did not find any resources to cool and dehumidify air when it is required to decrease from the ambient temperature in the box.
Any microprocessor can control sensors to make the measurements and issue control signals.
Dehumidifying and cooling such a small space could be a challenge. The usual method is to use a refrigerator-type compressor with cooling condensor and a water trap. You probably would have to circulate air from the box into some other apparatus to do that.
First, your box has to have a vent to the outside air as the inside air is heated. Heating and cooling will bring in outside air. So the way to reduce humidity is to exchange the humid air for dryer outside air.
There will also have to be wires from outside to inside and air will also migrate at that point.
Paul
For heating and cooling, it may be a good idea to see the Peltier elements. These elements are heated on one side and cooled on the other when current flows through them and when the direction of the current is reversed, the warm side becomes cold and vice versa. I guess with an H-bridge for motors it will be easiest to control such a module.
Thank you for your reply. I am open to increase the size of the box (20x20x20 inches or may be more). However, I am looking to build a chamber that can precisely control humidity and temperature in my required range.
yes I understand about the air migration while transferring the wires. I am planning to use silicon rubbers to seal the ports so that it reduces the air migration with the wires.
About the idea you shared on reducing humidity, if I bring outside air to the box, then the lowest humidity can be equal to the humidity that is present in the ambient. What if I have 40% RH in room and I want the box to have 20% RH? In that case, what can be used?
Sorry for not adding the accuracy with my post.
My desired accuracies are,
for temperature: +/- 2C or better
for humidity: +/- 2%
If this accuracy is hard to maintain, I am open to start with less accurate ones. After I have some experience on it, I can always try to achieve a better result.
Yes, I was assuming that I might need a dehumidifier. My question is while searching for a dehumidifier, can I use the commercially available ones? or Do I need to check some specifications on the dehumidifier that states I can use Arduino or any microprocessor to control that?
It'd be helpful for me if you could share some reference.
I apologize if I sound dumb. I am totally new to here and trying to learn.
So, then you intend to make you box expand like a balloon when you heat the air in the sealed enclosure?
The only way to reduce the water vapor in the air is to precipitate the water by cooling the air and with the proper heat sinks you may be able to do the with a Peltier device. But you have to get the cold side below the dew point of the air in the box.
Paul
Start small! If you haven't used Arduino before, it will take a while to learn to how to handle the various sensor types used to read temperature and humidity, and decide which might work for your project.
Then you can start thinking about control. PID control is usually needed, and there is a learning curve for that. It is a challenge just to keep the temperature of an object constant, so master that first for a small object, using a resistance heater.
Humidity control will be a much more serious challenge, and can be saved for last.
I am going to look at this differently.
a totally sealed box with 50% humidity at 70.0 deg F.
with no internal or external moisture variations, will return to exactly 50% humidity, when the box is brought back to exactly 70.0 deg F.
back to practicality. the heater should be so small as to take 5 minutes to raise the temperature in the box by 1 degree
and the humidifier should take 5 minutes to raise humidity by 1 percent.
you may think these to be extraordinarily long times, but if you can change the temperature by 1 degree in 1/2 second, you will need to slice that into hundreds in order to get any semblance of control.
the sizing of the device is critical to the successful operation.
think of an incubator. the egg breaths through the shell at such a slow pace that it might take a day to raise the humidity in that box. that means, a properly sized dehumidifier should be able to dehumidify 4 times faster than the process. or it should take 6 hours.
it is probably easier to control something larger than a shoe box or smaller than a box for copy paper.