Someone donated this old ultrasonic humidifier for us to tear down. I hoped we could get the speed control and maybe a fan out if it. But I didn't know if everything would be on a single PCB and therefore difficult to salvage. Luckily, all the main components were separate and the PCB only supplied the power.
So we wound up getting a bunch of good components that we can re-use. We also got some nifty tidbits that will be good for prop building. Check out the short video to see what we found...
It looks like the humidifier had gotten hit with a power surge. But this thing was sturdy and it still sort of worked, if very weakly. There was almost no mist or air coming out of it. Once we cracked the case we could see why. The surge had run in and fried the AC components. It's surprising that it still worked at all, but it made it easy for us to decide to salvage it instead of repairing it.
We tested the salvaged components and they all worked fine. My two favorites are:
- An all-in-one power switch with speed control and LED indicator complete with housing
- And a magnetic reed switch type sensor along with a floating circular trigger magnet.
Knob and Controls
The speed control is perfect for an Arduino project. It has three completely separate circuits going into the same housing to control three functions. There's a high current circuit to the on/off switch, a mid current to potentiometer, and a light-duty circuit to the LED.
I also noticed that they were using the potentiometer more like what I think as a rheostat. Even though the potentiometer has three tabs, they were only using two. But the tabs are accessible, so we can always add the traditional third line of the circuit.
With this configuration, you can turn the project on, then control an analog input with a single knob. The LED can be pulsed or blinked to give visual feedback.
And it's in a great housing that's really easy to mount into any project. It's circular and flat, so no weird shapes and curves to match. Just cut a hole, a big hole, into any enclosure and you have a very nice control panel - sweet!
Water Level Sensor
My other favorite find was the magnetic reed switch and magnet combo. This sensor is already on a slim PCB with a handy JST connector. And the floating ring-magnet is already sized to trigger the switch.
That's going to make using this as a water level sensor so much easier. These sensors and magnets are cheap to buy, but configuring them can be a hassle. When they come pre-matched and sold for use in fountains the price goes way up. So to get these for free was a pleasant surprise.
Overall, I'm very happy with the haul from this old humidifier. And the video was fun to make so I might start recording more teardowns. We have a room full of donated items, a huge random collection of semi-junk to tear apart and explore - loads of fun for the whole family - and much better than experimenting with items that still work.
