This is a simple relative humidity sensor support for the Ender 3. It also works on any printer that uses 20 mm x 20 mm extrusions, which means a lot more printers!

The sensor is mounted at an angle so that it is easier to read as the type of display is hard to read if you are not looking at it straight at 90 degrees.

As for the sensor, you can easily find it on Amazon and it is pretty cheap. I paid $20 for a pack of 5! Just search for "mini digital hygrometer" or try this link: https://www.amazon.com/Veanic-Hygrometer-Thermometer-Temperature-Humidifiers/dp/B07FCPJRFH/ref=sr_1_9?dchild=1&keywords=mini+hygrometer&qid=1594570646&sr=8-9

These little sensors come in many different shapes and sizes. The one I use is shown in the photos. You will need to push it in pretty hard and once the sensor is in it will be a little loose (go figure!). It's fine like that and it will never fall off. But if you're a bit of a perfectionist (like me), you'll want to prevent the sensor from rotating by adding a drop of glue in the back.

I also use these sensors in the storage boxes where I keep my filament reels once open to keep an eye on things. At $4 per sensor, why not! :-)

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