Singapore, a tiny little island at the tip of Malay peninsula, is probably one of the world’s most humid country. The average relative humidity (RH) level is 84.2% according to NEA, with thunderstorms occur on 40% of all days when RH can shot up to 100%.

As you may wonder how does this relate to electronics, look at this chip I dropped in my drawer 3 years ago.

Rusty chip
Rusty chip

For information purpose I list the storage humidity requirement for various items here:

RH% Items
50-60% Painting, Antique, Currency notes, Stamp, Book, Musical instrument, Jewellery, Leather products
40-50% Camera, Camcorder, Lens, Digital products, CD, Binoculars, Film, Video tape
30-40% Metal, Semiconductor products, PCB, IC, Battery, Precision equipment, Optical equipment
20-30% Raw medical, Dye, Seed, Pollen
<20% Special chemical products, Precision electronics components, BGA, LCD

Buying a dry cabinet is obviously the best approach. In fact I already have a small one for the cameras. But to store all my electronics and computer stuff I need a pretty big one, which costs a bomb, and I simply do not have the luxury of floor space. During a recent house cleaning exercise I decided to convert one of my wardrobes into a dry cabinet. Here is the victim:

Wardrobe in my room
Wardrobe in my room

There used to have a horizontal bar at the top for hanging clothes but I removed it. There are no shelves. A trip to IKEA brought me these wire baskets:

IKEA KOMPLEMENT basket
IKEA KOMPLEMENT basket

These baskets are not cheap (S$19/pc), but very sturdy and well below the cost of custom made shelves. I draw some marks in the wardrobe and start the irreversible modifications.

Markings inside the wardrobe
Markings inside the wardrobe

Here comes the main actor – the drying controller. I bought it from China taobao.com at RMB258 (S$52).

Dry cabinet controller
Dry cabinet controller

It is rated 6W/42W(max), control RH range 25%-55% with drying volume of 200L. I studied for a while and roughly figured how it works: the dry element is very similar to those we saw in “Thirsty Hippo” packet. There is a metal door in the controller. During drying operation the door opens inwards to let the dry elements suck the moisture from inside the cabinet; after a certain time the metal door closes, an electric warmer heats up the dry elements and dispels the moisture to the outside environment. The whole process repeats again and again until a pre-set humidity level is met.

To increase the effectiveness of drying, rubber strips are installed around the door frame.

Rubber strip along door frame
Rubber strip along door frame

And here come the final product :

Finished dry cabinet
Finished dry cabinet

During day time when my room humidity reads 69%, here is what inside the cabinet:

RH reading inside dry cabinet
RH reading inside dry cabinet

It doesn’t reach the advertised 25%. Maybe because the cabinet is not enough airtight and the total volume is larger than rated 200L.

I spend two weeks sorting all my components into plastic boxes. So far I’m pretty satisfied 😉

7 thoughts on “The battle against moisture

    • Actually it seems virtually impossible to make the wardrobe completely airtight. I set the controller to maximum and only achieve 38% RH after two days without opening the door. I can also hear the controller turns on quite frequently (once every 1-2 hours). For the power consumption part I’m not quite worried as it is rated max 48W.

      Reply
      • Yes I understand – which was why I asked if the controller was always on, trying to keep it dry. Still, it’s a good way to build your own DIY drybox though. 🙂 One day I’ll have to figure out how to buy stuff from taobao as well.

        Reply

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