as bharbour sayed , peltier would be the way to go if you want to diy a dehumidifier. You will need also a relay module, a arduino and a humidity sensor. And last , you will need a beafy power supply , because you will need to use at least 2 peltier modules. My dehumidifyer draws around 300W.

so i do need two peltiers, thanks. Any reliable ways to feed those 300w?

Give me a pm to talk more easly

You could use a Peltier cooler, but it is going to have a serious appetite for power. No moving parts beynd a fan or two. No refridgerant.

thanks! i can use this to tranfer heat, but my question is wouldn't i need two, i understand a dhumidifier has a double process in heating and cooling.

All the heat energy that goes into the cool side comes out of the hot side plus the energy from electrical power, so having an aluminum plate on the cool side and one on the hot side should do both jobs from one device. You would want enough physical separation or insulation so that the hot side does not feed back to the cool side to prevent it from cooling below the dew point.

I used to use one of the little car refridgerators to keep a sixpack of soda cool at work, and about once a month, I had to unplug it and warm it up enough to remove the ice ball that formed around the cool side. The fridge had a very small cool plate, so it got quite cold. A larger plate should pick up enough heat to not run below freezing.

You have not mentioned the application for this. If it is for dehumidifying a room, I suspect that it is going to be too small scale. If it is for a smaller space or to explore the idea, it may be adequate. 

Conventional refridgeration and air conditioning equipment just "transfers heat", using the physical properties of the refridgerant and the gas laws. The Peltier cooler does a similar thing with no moving parts.

well it's just for a room (pretty big room but not so much) i imagine though with what you say i can make it scalable by adjusting plates or something like that. wikipedia states that the hot side uses a heatsink to keep it at room temp, i suppose i have to keep it under so it can condense the water,

I can tell you what doesn't work. I tried to make a dehumidifier by plugging in a humidifier backwards. Major fail. 😜

But seriously as the others write you have to solve a cooling problem first. The control problem is minor compared to that.

Or buy lots of silica gel. 😛

yup silica gel and a fan is looking like a best solution ;). That reverse humidifier is now crossed out of the to-do list.

Hi @scaar3dontf3ar , you are probably not the first who would like to make the dehumidifier himself. There could always be reasons for that, you just have to clearly stipulate your reasons in order to have the best strategy. Be it cost, dimensions, efficiency, ...

I found some links, I'm sure you might have hit those entries too, if you want, feel free to share the links you already have so that they're not redundantly suggested.

As always the wikipedia entry is a good starting point :

https://en.wikipedia.org/wiki/Dehumidifier

From there, I've seen the dehumidifier certification program, I assume the safety in such devices might be one of the reasons they're not that easy to sell, so might be of interest to you so that your dehumidifier is safe :

https://web.archive.org/web/20080702004659/http://www.aham.org/industry/ht/d/sp/i/1225/pid/1225

Some other forums

https://physics.stackexchange.com/questions/88632/how-does-a-dehumidifier-work

All in all, it feels that the control program that in your case would run on arduino, is an important part, yet not representing the main challenge when it comes to the dehumidifier conception. But I might be wrong, I'm no expert in this.

So I think if your provide some links on how you would get started, that could narrow down the scope of your question. Hope that helps.

thanks!

Yes, that should work. But the refrigerator circle is a closed system typically made out of thin copper piping. So you either need to be really careful to not kink the pipes while bending them or you need to refill and seal the whole thing afterwards (which tbh I have no idea how to do).

You basically need something that creates cold - like a fridge. For better performance add a heat exchanger that pre-cools the air by warming the try air back up to room temperature.

Be aware that the cooling cycles of fridges or freezers contain coolant fluids that should not escape and sealing the cycle again can be tricky - especially if you have to ask here and think an Arduino is a good basis for a heat pump.

can i use fridge parts? i thought about the arduino becasue i saw a humidity meter done with it. I don't really expect it to do the work just have it trigger the rest of activation and deactiviation of it when a certain level, sorru i didn't phrase that correctly.

@scaar3dontf3ar Perhaps you mean you want to use a humidity sensor, an Arduino (or other microcontroller) and a switch for an existing dehumidifier? You could definitely do this with an arduino. The way you switch the dehumidifier is key - if you are switching 110V / 230V AC electricity you need to make sure you do so safely. It may be possible to use the arduino to operate the existing controls of a dehumidifier and these may operate at low voltage (3.3V / 5V) DC levels.