Humidity Activated Fan

In this instructable I will describe the steps required to reproduce my humidity activated fan prototype. During the elective 'Fablab making' at the applied sciences university of Rotterdam I spent the second quarter developing this prototype while learning to work with various machinery and iterate upon designs.

The idea is that as the humidity of the (bath)room rises, the fan is automatically activated to improve the airflow and distribute the humidity throughout the rest of the house. The bathroom in my apartment tends to get (and stay) very humid for a long time, even with the door open. Hence the idea to develop a solution for this issue. Unfortunately in my prototype I used a motor that was relatively weak which means that it could not really affect the airflow in any way, but this is something that can be improved.

The fan consists of two boxes, each box containing a microbit that drives the functionality.

In the first box, the smaller box with the holes and engraved humidity icon, the microbit with the humidity sensor is contained within. This microbit checks the humidity every 15 seconds and then it decides wether or not to tell the other microbit to turn on the fan, based on the humidity treshold that is set. In my case I set 70%.

The second box with the fan contains a microbit that receives the signal from the first box and engages or disengages the motor to spin the fan when it receives the corresponding command.

Initially I was also planning to include a lamp on the fan. You can see this represented on the paper prototype on the left of the picture. The yellow bulb-like thingy in the middle of the fan. But I decided to let that part slide as it was a bit out of scope for this project and added unnecessary complexity to the process.

Required supplies

• Wood suitable for lasercutter
• Thickness 4mm
• Dimensions AT LEAST 50cm*30cm (or 500mm*300mm). If you decide you also want the stand for the fan box, you will need an additional piece of wood of 15*15cm (or 150mm*150mm).
• Microbits & Accessories
• Two microbits
• https://www.kiwi-electronics.com/en/bbc-microbit-v2-2-single-10222?ff1=25&search=microbit
• Battery pack
• https://www.kiwi-electronics.com/en/bbc-microbit-boards-kits-accessories-276/2x-aaa-batterijhouder-met-jst-stekker-aan-uit-schakelaar-3826
• Grove shield for microbit
• https://www.kiwi-electronics.com/en/grove-shield-for-microbit-v2-0-3221?search=grove%20shield%20microbit
• Grove compatible DHT11 sensor + connector to grove board
• https://www.kiwi-electronics.com/en/grove-temp-humidity-sensor-dht11-2061?search=dht11
• https://www.sossolutions.nl/grove-universal-4-pin-buckled-20cm-cable-5-pack
• Kitronik motor driver board
• https://kitronik.co.uk/products/5620-motor-driver-board-for-the-bbc-microbit-v2
• 9V 6LR61 battery + connector to motor driver board
• https://www.amazon.com/Amazon-Basics-Performance-All-Purpose-Batteries/dp/B00MH4QM1S/ref=zg_bs_g_389576011_d_sccl_1/145-4403637-2955617?psc=1
• https://www.amazon.nl/JZK-Connector-transistor-connector-Batterijen/dp/B09TT9W653
• Kitronik DC motor
• https://www.kiwi-electronics.com/en/dc-gearbox-motor-tt-motor-200rpm-3-6vdc-10318?search=dc%20motor
• Sticker paper suitable for the vinyl cutter
• Dimensions about 10cm*10cm, but possibly larger/smaller if you decide on a different design.
• A set of thumbtacks
• At least 40 grams of PLA filament for the 3D printer.
• Tiewraps 2.5mm*100mm

Required tools, hardware & software

• Machines
• Lasercutter with ability to cut at least 4mm plywood
• 3D printer with enough clearance to print an 18cm tall diameter fan. With 20cm vertical clearance you should be good.
• Optional: A vinyl cutter for the sticker on top
• Tools
• Wood glue
• A screwdriver and a few very short 2mm screws
• A small flathead screwdriver
• Sandpaper / wood file
• Laptop
• Patience and still hands
• Software
• Inkscape (or other vector based design application equivalent) https://inkscape.org/release/inkscape-1.3.2/windows/64-bit/msi/?redirected=1
• Tinkercad (or other 3d modeling application equivalent) https://www.tinkercad.com/dashboard
• Boxes.py https://boxes.hackerspace-bamberg.de/FlexBox?language=en
• Configuration for humidity box: x=140, y=140, h=40, thickness=4.0, FlexSettings: distance=0.35. All the other settings are left as default
• Configuration for fan box: x=110, y=140, h=110, thickness=4.0, FlexSettings: distance=0.35. All the other settings are left as default
• Microbit makecode https://makecode.microbit.org/#edito

As a first step I would recommend to plan ahead and decide upon the design and if any changes are necessary.

Do you have all the required tools and supplies? Or do they deviate in some way? Are you going to use a different motor, or a larger fan? These all impact the design significantly.

Say for example that your wood is thicker than 4mm, then you will have to make a new design for the box as the thickness of the wood has impact on the bendability of the model that boxes.py generates. In case you only have access to thicker wood, you can use the settings I listed under tools and change the thickness according to your wood.

In addition, there are some other components that may vary. If you are using a different motor for example, you will have to change two things. For the box you will need to adjust the cutout according to the dimensions of the motor. And if the connecting part between the motor and the fan deviates as well, you will have to measure it and adjust the model of the fanblades too.

In all cases I recommend testing and experimenting with the dimensions of cutouts. Both for fitting the parts, as well as the bendability in the case of wood. By testing and verifying the dimensions, you can be sure that you are not wasting material and time as there's likely always something unforeseen. When working on the 3d-print I initially printed a small 1.5cm block with cutouts for the fitting to the motor to verify that the dimensions are correct and that it fits. In the case of wood I actually made a mistake by following the default boxes.py design, which caused it to break upon bending. As you can see in the pictures above!

Before you can assemble the parts, you'll have to make them. In this step we will be using the lasercutter and 3d printer.

Lasercutting

For the lasercutting you will want a large piece of wood of 4mm thickness. You can cut the boxes seperately (With files LASERCUTTER_FanBox.svg and LASERCUTTER_HumidityBox.svg) or in one go (With file LASERCUTTER_Both_boxes_template). I personally recommend cutting them in one go as it is faster and ensures that you are using your material optimally. Are you planning on using the stand? Then do not forget to also cut the FanboxStand.

You'll need to download the svg files of these cutouts onto the lasercutter. Make sure that the lines are all correctly placed and that the machine is configured appropriately to cut them as 4mm wood, cutting in 0.01mm thickness. Place the wood into the machine, calibrate the laser and start lasercutting. Let the machine clear the air and wait a little bit before picking up the wood. If the edges are rough, use the sandpaper or wood file to grind them down a bit.

3D-Printing

For the 3D printer you will need to download the 3DPRINTER_Fanblades.stl file onto the 3D printer. In my case I also had to use Prusa software to prepare the STL file appropriately and configure the printer that way.

Prior to printing, you will also want to tilt the model to such a degree that the printer does not have to create too many supports. You can see this in the video above, I tilted my fan vertically instead of keeping it horizontally on the bed of the printer. This will create smoother blades for the fan, as well as save time because the printer does not need to lay down as many supports.. I recommend turning the model of the fan about 60 degrees vertically prior to printing, to allow for efficient supports. For this print I did not apply a brim, but you can if you feel safer doing so. If everything is set, then you can start printing. Make sure to stick with the printer for the first bit to verify that everything is running smoothly. After the printer is done, remove the print from the bed and supports very carefully because the fan blades are fairly fragile. With the supports removed the print is done.

Now that you have all the parts done, it's time to assemble the boxes. You will need the woodglue for this part.

Aligning the parts

Start with the humidity box.

Take the bottom piece and lay it on the table. Then take the long, bendable side piece and carefully wrap it around the bottom piece, while aligning all the little finger joints in the wood. Does everything fit snugly or is it too tight? If it is too tight, use the sandpaper/wood file to grind some wood away to allow for some more space. Repeat this for the bendable piece and the lid, you don't want the lid too tight either.

By fitting the pieces together this way you should be able to see where the contact points are where you need to apply glue. Both on top of and on the inner sides of the finger joints on the bottom part, which is where the finger joints from the bendable part will touch. If it's not clear for you where to apply glue, try fitting the bendable piece over the bottom piece again and pay extra attention to the finger joints.

Glue them together

For the glue you will only need to apply it to the bottom part. You can apply glue to the top of every finger joint, as well as on the inner side where the 'walls' of the bendable piece will make contact. After applying the glue to the bottom piece you can wrap the bendable piece around the bottom piece. Try not to make a mess with the glue. When you have the bendable piece glued to the bottom piece, you will need to hold it still for about ten minutes while the glue settles. I recommend keeping pressure on the place where the two ends of the bendable piece meet eachother. This way the wood can not move. Maintain this for about ten minutes or so.

After you have glued the bendable piece to the bottom piece and waited for it to settle a bit, it is time to place the lid. By placing the lid on top you ensure that the walls of the bendable piece will settle straight up, instead of them possibly bending inwards a bit. Do not glue the lid however, we need it just to help shape the box. When you have the lid placed on the box correctly, and the side is still glued on to the bottom piece, I recommend laying the box on the side with the ends of the bendable piece and placing a few books on top so the glue can settle. Leave the box this way overnight.

Now that you've successfully assembled the humiditybox and have some experience with the flexible wood, you can repeat the steps above for the fanbox. In this case you will want to be a little more careful however. Because the box is taller it can be a bit more tricky, especially to place the lid at the end.

In this step we will prepare the microbits with their code and components and run a quick test if everything is working as it should.

Humidity microbit

For the humidity microbit (Shown in the picture on the right side), we start by connecting the microbit to its grove shield. Then you take the DHT11 sensor and also connect it to the grove shield, using the four pin connector cable. Connect it to data pin P0 on the board. Now connect the microbit to your laptop using the micro usb cable. That's as far as configuring the hardware! It should look a bit like in the picture.

For the software you'll need to download the 'MICROBIT_CODE_HUMIDITY' file and head to https://makecode.microbit.org/ . Here you can use the button 'import'. After importing it, you need to download it to your microbit. Now your humidity microbit is ready! Disconnect it from your laptop, but leave it assembled for the test.

Motor microbit

For the motor microbit (Shown in the picture on the left side), we start by connecting the microbit to the motor driver board. You will also need the small flathead screwdriver for this part. Take the connector for the 9V battery and attach it to the motor driver board on the port that says 'power'. Make sure to connect the ground and positive wires on the right nodes, also visible on the board. Then screw them tight. Now for the motor. Take the motor's wires and connect it to the 'motor1' port, connecting the ground and positive wires to the right nodes. Then screw them tight. Now connect the microbit to your laptop using the micro usb cable. That's as far as configuring the hardware for the motor microbit. It should look a bit like in the picture.

For the software you'll need to download the 'MICROBIT_CODE_MOTOR' file and head to https://makecode.microbit.org/ . Here you can use the button 'import'. After importing it, you need to download it to your microbit. Now your motor microbit is ready! Disconnect it from the laptop. We can now test the microbits.

Running a test

For the test you will need to power the microbits first.

In case of the humidity microbit, you can simply connect the batterypack to the white power node on the microbit itself. In case of the motor microbit you have already attached the 9V battery connector, you now only need to connect the battery to it. Now both microbits should have a small LED emitting light, indicating that they're ready for use.

For the test, you can simply click on the 'A' button on the humidity microbit. Now you should see that the motor from the other microbit starts spinning. If this isn't the case, make sure that everything is connected correctly. If everything is connected correctly, something may have gone wrong with downloading the code. Verify these parts until the test works.

With everything functional you can disassemble the microbits, but do not get the microbits mixed up as in the next step they will be installed in their respective boxes.

Now that we have the boxes ready, we can start installing the hardware and get to the end of this project.

Humidity box

For the humidity box, we have three main components that we have to install.

The microbit (with grove shield), the DHT11 sensor and the battery pack.

For the microbit and the DHT11 there are nice holes on the PCB which we can use to connect them to the wood. For this purpose you have some thumbtacks that you can stick into the wood. They are simple to attach and detach and require little effort. The microbit has two holes that are suitable for thumbtacks on the right side. I recommend placing the microbit with its left side to a wall in the box to make it more stable. Make sure to keep access to the important ports and power node. You can use two thumbtacks to fasten it to the wood. The DHT11 sensor has three holes in which you can also use thumbtacks, with three thumbtacks it will be plenty stable so you can place it anywhere there is space in the box. See the picture on the left for the placement of my prototype.

Then the batterypack. It has one screw hole in the middle for which we need the tiny screw and screwdriver. Remove the batteries from the pack while you are installing it. Place the empty batterypack in the box, somewhere where there is space and where the cable is in range of the microbit. Then apply the screw and fasten the batterypack to the box. Then put the batteries back.

With all the parts assembled in the humiditybox, it is finished. Now to finish off the motor box

Motor box

For the motor box we will need thumbtacks and the tiewraps.

For placing the battery there is space on the back side of the box where there are also the cutouts for the tiewraps. You can place the battery here and subsequently use the tiewraps to fasten it to the wood. Make sure that there is no leeway for the battery to move after fastening the tiewraps

After placing the battery you will want to place the motor. The motor can simply fit in the cutouts and should already be fastened fairly snugly by the friction, but to be safe you want to attach a tiewrap between the cutouts near the top of the motor. Make sure that you place the turning axis of the motor outside of the box, because else turning the fanblades will be hard.

Lastly you will need to fasten the motor driver board with the microbit on it. The motorboard has convenient holes which you can use for the thumbtacks or screws. Make sure that the cables connecting the board to the motor can reach the board because else you'll have to do it all over again. When you are sure of the placement of the board, apply the thumbtacks and fasten the motor board to the box.

Fan

Attaching the fan is possibly the simplest part of this project. Simply align the hole for the motor to the motor and gently press it on. It should fit snugly and stay there without any glue or adhesive.

Stand (Optional)

If you decided to print the stand you can assemble it by simply connecting the pieces of wood to eachother. You have two 'leg' pieces and a 'beam' piece. Each piece has a small 5mm cutout to allow a wood on wood connection. You can simply click the beam piece into the leg pieces at the cutouts and your stand is done. If you want you can glue the stand to the bottom of the fan using some wood glue. If you forgot to cut the stand but do want it, you can move back to step 2 and cut it seperately.

Sticker (Optional)

Unfortunately my sticker design is not possible to reproduce because while cutting the sticker, the paper got loose and the machine ended up cutting something else entirely. I like that design even more to be honest, but I can not share it unfortunately. I will attach a sample sticker to this step regardless

The process of cutting a sticker is fairly simple. Simply place the material into the machine correctly and send the .svg file to the machine. It will cut out your sticker afterwards. When the sticker has been cut, you can peel it loose and apply it to your prototype.

You're all done!

To turn the fan on, you simply have to connect the circuits to their respective power supplies. Enjoy!

There are some possible improvements for this project, such as the layout of the boxes, the power of the motor and also the fan itself. The boxes are currently a bit on the large end for what they do. The motor is also very weak and doesn't affect the airflow. The design of the fan is generally okay, but the angle of the blades could be a bit steeper.

Supplies

• Two microbits
• https://www.kiwi-electronics.com/en/bbc-microbit-v2-2-single-10222?ff1=25&search=microbit
• Battery pack
• https://www.kiwi-electronics.com/en/bbc-microbit-boards-kits-accessories-276/2x-aaa-batterijhouder-met-jst-stekker-aan-uit-schakelaar-3826
• Grove shield for microbit
• https://www.kiwi-electronics.com/en/grove-shield-for-microbit-v2-0-3221?search=grove%20shield%20microbit
• Grove compatible DHT11 sensor + connector to grove board
• https://www.kiwi-electronics.com/en/grove-temp-humidity-sensor-dht11-2061?search=dht11
• https://www.sossolutions.nl/grove-universal-4-pin-buckled-20cm-cable-5-pack
• Kitronik motor driver board
• https://kitronik.co.uk/products/5620-motor-driver-board-for-the-bbc-microbit-v2
• 9V 6LR61 battery + connector to motor driver board
• https://www.amazon.com/Amazon-Basics-Performance-All-Purpose-Batteries/dp/B00MH4QM1S/ref=zg_bs_g_389576011_d_sccl_1/145-4403637-2955617?psc=1
• https://www.amazon.nl/JZK-Connector-transistor-connector-Batterijen/dp/B09TT9W653
• Kitronik DC motor
• https://www.kiwi-electronics.com/en/dc-gearbox-motor-tt-motor-200rpm-3-6vdc-10318?search=dc%20motor

Software

• Software
• Inkscape (or other vector based design application equivalent) https://inkscape.org/release/inkscape-1.3.2/windows/64-bit/msi/?redirected=1
• Tinkercad (or other 3d modeling application equivalent) https://www.tinkercad.com/dashboard
• Boxes.py https://boxes.hackerspace-bamberg.de/FlexBox?language=en
• Microbit makecode https://makecode.microbit.org/#editor