1 Jan
Air Cooler v2
Its been hot and dry this week, so today I built a home-made humidifier. I started with version 1 and then got a little carried away.
Version 1 comprised a fan and strips of cloth which dangled in water. This system worked well, however, it required a manual process of periodically dipping the cloth into a trough of water. Therefore, automation was in order and thus version 2 was born.
Version 2 also makes use of a fan, strips of cloth and a trough of water, but introduces two Lego motors and an NXT brick. The first motor drives a winch which lowers and raises the cloth in and out of the trough of water. The second motor switches the fan on and off.
Top down view of the humidifier
Hardware
Like most software developers I hate hardware, and due to my lack in engineering skills it took me most of the afternoon to rig up the system of strings and pulleys. In the interest of not wasting more time on the hardware, this section will be short 
The original version 2 featured weights to counter the weight of the wet cloth and lighten the load on the winch motor.
Using a scale to work out how much counter weight is required.
In the end I got rid of the counter weights and made the cloth shorter instead. The cloth is stapled to a short wooden dial which is suspended from a pulley mounted at the top of the main wooden frame. I used piles of cable ties to stick the Lego bits to the wooden frame and the fan.
Close-up of the Lego bits
As seen in the picture above, the Lego motors are tied to the wooden frame to drive a winch, and to the fan switch to control the fan.
Software
The reason I embarked on version 2 was to automate the ‘dipping process’. The software loaded onto the Lego NXT was written in Java, and looks like this:
| for (;;) { | ||
| sleep(60*10); // Sleep between dips | ||
| switchOffFan(); | ||
| sleep(4); // wait for the fan to spin down | ||
| lowerCloth(); | ||
| sleep(60); // Sleep while the cloth is in the water | ||
| raiseCloth(); | ||
| fanSpeedOne(); | ||
| } | // Rinse and repeat – quite literally. |
The program is simple, every 10 minuets the fan is switched off and the cloth has a swim before being raised back up the wooden frame, followed by the fan being switched on again.
Why switch the fan off and on? Lowering the cloth while the fan was switched on caused the cloth to get caught on the wooden struts.
We’re running a test to see how fast the water in the through is depleted. I’ll update this post with the results
The cloth being blown by the fan.
