The Grow Machine

The Grow Machine

This machine is an incubator for growing mycelium, the roots of mushrooms. It provides variable growing conditions in order to suit a variation of species which have different processes when growing. The machine allows a user to control temperature, humidity and light while also providing a clean, contamination free environment with the use of a laminar flow. The aim of the Grow Machine is to grow mycelium based material but growing mushrooms is also very possible.

Why Mycelium?

Mycelium as a material has many desirable characteristics that are useful in the material world, such as being fire retardant, water resistant, light weight, strong and most interestingly to me self growing with little resources. The best thing about mycelium is that it is also biodegradable if you throw it on a compost heap, not only breaking itself down but recycling other nutrients into carbon and nitrogen rich soil for healthy plants to thrive on. As well as being vital in the natural world it is a really powerful material, one that hasn't reached its full potential yet so this project is about bringing awareness to mycelium and making the growth of it as a material easy for amateur biologists. I would love for this project to make people think more about what they consume and think of alternative ways of producing material goods.

Why these variables?

Mycelium's natural habitat is in a dark wet place like soil or tree stumps when it is not too cold for example frost would kill the mycelium. So by providing heat, humidity and a lack of light is the closest to imitating it's natural habitat. The clean air is not imitating nature but as the purpose of the machine is to grow material we want to reduce the possibility of contaminants which could hinder the quality of the material.

Tools

Martin jointer and planer

Table saw

Router table

Festool Domino

Metal chop saw

Miter saw for wood

Laser cutter

Waterjet CNC cutter

Hand drill and a wise selection of drill bit

Pillar drill for metal and wood

Manual Metal Lathe

Manual metal Mill

Horizontal metal band saw

Sanding machine for metal and wood

Tin snips

Hand tap

Measuring tools :

Set square

tape measure

Center punches

Terms I use:

Before I get too involved in the process of making I am going to clarify a few words I use often:

Incubator/growing chamber - this is the section of the machine that is providing the growing conditions for the mycelium, it is the section contained by windows where the growing will be happening within a clean environment provided by the laminar flow. The other side of the machine facilitates the control panel and some overflow shelving for any mycelium that has finished growing.

Laminar Flow - this is the combination of a high quality filter and a blower the pushes air through the filter to make the space above the filter clean from particulates that could contaminate the mycelium. In science the term laminar flow actually means the movement of air in a straight line but in this case I refer to it as the blower and filter making the incubator free from contaminants

Controls - I refer to the wiring, programmable micro controller and appliances as the controls because this is the system that controls the growing conditions in the incubator.

One of the aims of this project is to make mycelium growing attractive so that more people are interested in trying out the world of mycology within the biomaterials realm. Therefore this incubator has been produced in wood so that it could be seen as a piece of furniture in our homes. For anyone who is a mycology geek like me, you would know that mycelium loves growing on wood, its one of its preferred substrates for growing, but we want to control the environment inside the incubator to mitigate the possibility of contamination. If the inside of the incubator was wood it would allow spores to start germinating on the structure which in turn could contaminate alternative species that we are trying to grow. So to eliminate this potential problem, the internal surfaces will be clad with aluminum, more on this in later steps.

I used oak because I am familiar with the material, I trust its strength and it doesn't get affected by moisture like other species could do which might be a problem when creating a high moisture environment despite the help of the aluminum profiles. I also like the light, bright color of oak. The specific oak I used is white oak. You could also opt for Cherry, Ash, Mahogany and Teak which are all suitable for moisture conditions.

If you are in the Bay Area, California, you could visit the awesome wood store I picked my wood up from Macbeaths

Jointing

Once I collected my timber I dived straight in to joining it on the Martin Jointer. I scribed the side I was jointing with a pencil with a scribbled line so I could tell if the whole length of the timber as been skimmed by the blade; once all the pencil has gone you know you have achieved a flat surface. The bed of the machine was set to take of 1/32 inch. In some cases I needed to take a couple of layers off to achieve the flat surface. I started with the width so I could use this wide surface as the guide to joint the height.

Planing

Once you have two sides jointed (one width and one height) you can move on to the planar. The planar works by lowering a series of cutting blades to a desired height towards a flat bed, which means the flat side you just jointed is placed on the flat bed and the cutters take layers off of the non-jointed wood to make sure they are both parallel to each other.

I am cutting the timber profile to 40x40mm/1.75x1.75inch which as been carefully worked out in relation to the other profiles and components being used so by taking small layers of wood (any where between 0.3 - 0.6mm) at a time I reached my desired height of 40mm

Cutting the profiles on the table saw

Now I have a series of boards that I know are the correct depth of 40mm but need to be cut into 40x40mm batons using the chop saw and table saw. At the moment my boards are much longer than I need and because I will be using the table saw to cut through thick timber it would be safer it they were shorter pieces. I used the chop saw to cut the lengths to the correct dimensions, by doing this when the timber is wide meant that I knew they would be the exact same dimension as they had been cut with that same cut. With all my lengths cut I took them to the table saw. Before I cut anything I needed to change the blade for one that is designed to cut hardwood, these typically have less but larger teeth. I measured the width from the blade to the fence precisely using a caliper. Using feather board guides (moving them each time the width changed) I pushed the board through the blade with enough speed and pressure that it wouldn't burn the edge of the wood. Repeating the process until I had all the pieces cut and plenty of left over (incase of any mistakes or poor timber sections)

The wooden frame is the main structure of the machine so this is the first part of the construction. However as there are many components that need to be added in a systematic way you need to leave the gluing of the frame to the end so that you can add pieces and modify parts as you work through the project. It is important for my thinking process to see the form in reality as I am planning and ordering parts so I can actually measure pieces that I have estimated, this eliminates wasting money and time on details and materials that may change when you make it, luckily for you I have gone through the trials and tribulations for you so it should be much more straightforward. The process of putting the frame together was vital in making sure I was routing groves for glass and drilling holes for shelf pegs into the correct parts as its easy to get confused when there are so many parts.

The main frame structure is made from 40x40mm white oak batons (if you chose the same timber as me) which is constructed with butt joints. These butt joints are strengthened with two domino pegs per joint which gets quite confusing when there are 27 pieces of wood all coming together to make the frame. I set up a coding system when laying out my pieces and had a methodical way of working through the sections.

Choosing the right domino, knowing my piece was 40x40mm and that at some junctions there would be up to 3 pieces of wood coming together I chose a 30mm domino peg which would insert into the wood by 15mm. This would be strong enough but not interfere with the other peg coming in from the other side. The matching peg was 5mm thick so I inserted the corresponding drill bit into the tool. I set the travel of the tool to 15mm so the holes were correct to the peg I would insert into them.

I started with laying out the front part of the frame on a large table. At each joint I labeled both pieces of wood with letters so I could find the joints if the pieces get mixed up. I wrote the letters on the part of the wood that would be covered with the joint, mainly so I would know which part of the wood matched up, this also helps by covering up the pencil marks without having to sand them off. I marked the center of the joint and used my set square to draw a line over both pieces of wood as this is the reference line you need for the domino tool. It doesn't matter if the line is perfect because the most important thing is that the lines match up with each other so the domino peg aligns the pieces correctly.

I set up a clamped jig with pieces of scrap wood and the fence of the table saw so that I could place pieces securely and quickly without having to clamp each time. At each joint are two domino pegs so I used the guides on the tool to set two heights that would be in the fit place as well as easy to switch between the two. For the lower height I used the top of the gauge and for the top height I used the '16' marker. I did a couple of test cuts before starting with my pieces. I started with the lower height for all the pieces using my jig to quickly move through the cuts, then I went through the cuts again in the top height which eliminated the need to switch the heights for every piece. This was the most efficient way of making the cuts.

Once I had made the cuts for the first part of the frame I used a mallet to insert the pegs and join the pieces of wood to check I had measured correctly and that the joints align as expected.

I repeated the process with the back side of the frame but using numbers instead of letters for the coding so I knew which side was which. Once I had both front and back sides put together I places the connecting pieces in the correct places so I could see it as a complete piece (at the moment everything is on its side on a table). I then coded the joints again, using letters for the front side and numbers for the back side. I marked the center lines again and repeated the process of making the domino cuts, doing the top cut first then the bottom. This is where I faced a problem I foresaw but was unsure how to solve it until I saw it for myself. At most joins there are three pieces of wood connecting which means there are two sets of domino pegs that collide, in order to construct the frame with both sets of dominos I had to cut one down to shorted it so it wouldn't clash with the colliding domino, this worked well and meant that the structure is still strong by having two dominos per joint.

I tested that the frame fits together as a whole but there is plenty more to do before being able to glue the frame together. Lets move on to the details needed to make other parts fits correctly

There are lots of components, parts and details that all fit together and have been designed in a way that conceal the parts that should be concealed to make everything look aesthetically clean and simple.

Firstly the aluminium equal angle that goes on the internal edges of the incubation chamber has a fillet, in order for the profile to connect to the upright there will need to be a small chamfer on the edge it will cover. This is achieved by using the router table and a chamfer bit that has the correct radius. It doesn't matter if you take too much off as this will be covered by the aluminium. The best bit to use will be a bit with a bearing so you can run the piece along without needing the fence. Remember to chamfer the correct edge by marking with coloured tape which edges you need to keep.

Routed grooves for poly carbonate

The poly carbonate panels on the incubator side sit within the frame and the smart tint film has copper strips that need to be concealed so groves will need to be cut into the timber uprights. It is helpful if you code the uprights with a clear system like numbers or letters and to tape a marker on the edge that will be facing outward to help you visualize where the cut needs to be so everything lines up. Measure and mark which cuts need to be where, remember you have 2 x 6mm panels, 1 x 3mm panel and a hinged door. See drawings showing the different profiles needed to be cut.

Using the router table and a drill bit that matches your poly carbonate thickness, ideally a fraction larger diameter as there will need to be a little tolerance. I used 6mm poly carbonate and a 6mm router bit which meant I had to make the first cut then shift it over to make the extra clearance for the sheet. You will need to correctly align the router bit so the aluminum meets the edge of the cut which should be 17.5 if you used the same as me. We don't want to run the cut the whole length as we would see the routed grove at the top where the end is exposed but because we need to slide the polycarbonate into the frame we need to go in from the bottom. The groove will simply need to stop just before the top end so you can put a pencil line where you need to stop moving the piece which should be 30-35mm from the top end. If the groove doesn't go far enough you can always take a little bit more off with a chisel when you are actually installing the panels.

The routed grove needs to be 5mm deep.

Always do a test cut to check the measurement is correct.

Using feather boards to secure the timber take a portion of the depth out in the first cut as it is too much for the blade to take the full depth away, remember that sawdust has to go somewhere so its best to do a couple of passes increasing the depth each time. Do all the profiles at the same height in one go, then increase the height and do them all again at the new height so you don't need to keep moving the bit.

Once you have the cuts, check that the poly carbonate fits with a little bit of wiggle room, remember the smart film will add to the thickness too.

Top cross bars

The top cross bars on the incubation side also need a groove to for the poly carbonate to fit into and to conceal the copper strips and wires for the smart tint. This groove will need to be deeper to allow for the wires which should be about 10mm deep. Make the cut in increments so you can test how deep you need to go to hide the wires, you may want to make the groove a little wider too as the solder on the wires may protrude a bit meaning that the panel wont easily slip in.

The top cross bars also need a large champfer so that the wires from the panels can be concealed behind aluminum angles. Using a router bit that has a champfer profile cut the internal edge of the 4 top cross bars in increments, you will be sticking the aluminum with double sided tape so the champfer needs to leave some surface area that the tape can stick to while still being significant enough that the wires can run along the channel.

The panels for the incubation chamber are what makes the chamber dark. They consist of polycarbonate panels with Smart Tint electrically charged film applied to the internal face which switches between opaque and translucent, when switched off it blocks 96% of light (opaque) and when switched on it blocks 33% of light so you can see inside (translucent - similar to sunglasses) This blocks out some light so the incubation chamber is providing a darker environment, which imitates mycelium's natural habitat under the soil (for most species).

You can order the polycarbonate panels from most plastic suppliers. The size for the two panels opposite and adjacent to the door are 880x315mm, this is allowing 5mm extra for the three sides that slot into the channels you will have already routed. At the bottom the panel sits on top of the timber cross bar rather than within a channel. The door panel is 840x270mm. These are the same dimensions for the smart tint you will need to order, specifying that the wiring is at the top and accounting for the sticky side being on the internal face of the windows.

The film has a copper strip at the top and an adhesive backing, the copper strip should be concealed in the channel you cut on the router table, if it is not concealed enough you may need to make your groove deeper. The two wires soldered to the copper strip will need to be bent to run along the top, again making sure you have enough space in the groove. You can do these tests before you stick the film down. When you are ready to apply the film follow the instructions from the smart tint website here

The machine has been designed to conceal all the cables within the cavity between the incubation chamber and the open shelves, which is where the heat pads are also concealed.

The cables for the smart tint panels run along the top of the incubation chamber, hidden beneath aluminum channels, these are the cables that need to be allowed for in parts of the frame so that they can be concealed nicely. There are also cables running from the control panel down to where the relays and power supplies are near the blower which need to fit through holes in the frame. All the holes made for the cables should be invisible when everything is put together.

Chiselling grooves for the smart tint wires
The wires for the smart tint panels will fit nicely in the champfered edge of the top cross bars of the frame that you just cut, beneath the aluminum profiles so that you cannot see them, but they also need to bend round the corners so space needs to be provided for this to happen. I did not design the types of cuts I needed when I modeled the 3D version as it is easier to see in real life what parts need to be removed. The best approach is to place the panels in place and lay the wires into the position, then marking lines on the timber as to what part needs to be taken away to allow for the wires to sit in a little pocket beneath the aluminum profile can sit on the face of the timber without colliding with the wires. It is a bit of trial and error, taking away material in increments and testing if you've taken enough away and in the right place. The pictures show how it might look.

Control panel wiring

For the cables coming from the control panel down through the cavity the hole in the side of the control panel needs to be large enough to feed the sensors through and to run all the cables from the metro mini board out. To do this you could use the chisel and remove the material slowly, this could be difficult as the hole you need to make is at a right angle going in from one face of the timber upright then turning a corner and coming out the adjacent face. Using a hand drill you can drill three large holes next to each going half way into the timber profile, then using a chisel turn the three holes in to a rectangular hole. Repeat this on the other side using a set square to line up the holes, going deep enough to meet the first hole you made on the adjacent side. Using the chisel to neaten the hole you've made.

At the bottom where the wires need to get from the cavity in the middle to where the power supplies and relays are you will need to drill a series of holes in the middle cross bar, similar to the step before with the three holes and a chisel to neaten up the edge, however this time you want to go the hole way through so the wires can go straight into the bottom section invisibly.

The only cable that will be visible will be for the humidifier as this is an appliance that actually sits in the incubator.

Cutting the aluminum lengths for the internal edges

The reason for the aluminum is to ensure the internal part of the incubator is sterile. Timber is a beautiful looking material but mycelium loves to grow on it so if the timber is exposed on the inside where the mycelium is growing then we could have a problem on our hands. The polycarbonate panels slot in to routed groves in the timber uprights which meet the edge of the aluminum so the dimension of the angle is important to get right. I used a 19mm angle which had an internal dimension of 17.5mm for the sides the would have the 6mm polycarbonate and the door. For the uprights that are in the center (with the solid panel) these have 3mm polycarbonate and need as much space for the cavity between the solid panels as possible (for cabling and heat pads) so the configuration of aluminum and polycarbonate is slightly different, see drawing, so I used 19mm flat bar instead of an angle.

I used the metal chop saw to cut the aluminum angles which I measured and marked against the frame I just put together to ensure it will fit. As I bought 4ft lengths of aluminum I would have enough for the short edges at the top.

As the internal part of the angle had a radius I need to route away a radius on the edge of wood that it would join so the could sit snug together, I used a very small router bit with a bearing so I didn't need to use the fence for guidance. Because I have the end grain of the upright posts visible I needed to make I didn't route the radius all the way to the end as this would be seen, the same goes for the routed groves for the glass.

Making the pegs for the shelves

The aluminum pegs that hold up the shelves are cut from a 7mm diameter aluminum rod at a length of 25mm. The will push fit into 7mm holes in the upright profiles of the timber frame and will go in by 10mm so 15mm will be exposed to the shelves to slide onto.

I used the DoAll horizontal band saw to cut the pieces. Before I made the cut, I used the circular sanding disk to bevel the end and neaten up the rough face. I measured 25mm with a tape measure and marked it with a scribe. Using the laser guide on the horizontal band saw I eyed up the marked line, knowing that it wasn't imperative for the dimension to be perfectly correct to the decimal point. Once I made the cut I then repeated the process, beveling the end first, measuring and cutting. To neaten the newly cut side I placed the small peg into a pair of pliers and sanded off the rough edge.

Drilling holes

Once I have all the pegs I set up for drilling the holes. I checked where the right upright posts need holes,
I had another coding system with tape that identified the post with the hinges. I taped all the aluminum in position tightly, (I didn't want to glue it incase I needed to remove it for an unforeseen detail in the future). I used my tape measure, set square and scribe to mark on where the holes are and a wax pencil to circle the marking for easy visibility. I punched a marker hole for the drill bit to center on and then with my vise clamped to the bed of the drill I used the counter sink drill bit to drill a small hole first, doing this for all the holes, then I drilled an 6.9mm hole for the final dimension. I went through both the aluminum profile and the oak setting the drill direction to stop at 10mm into the wood.

I fixed both the pegs and the aluminium angles with strong adhesive glue suitable for metal and wood.

The door frame is made of the same oak as the frame, and just like the other panels that surround the incubator chamber it also has smart tint film on the internal face. The general approach to the door is to build a thin frame which has routed channels for the panel to fit in and to drill a hole for the wires to exit on the hinge side closest to where the wires can be hidden in the aluminum angles running along the top.

Cut the frame

The frame profile is 20x17mm, the 17mm is the depth so there is clearance between the door frame and the internal aluminum channel. Make sure to mark which side is which to avoid confusion as the dimensions are very similar. Using the table saw, with a hardwood blade cut the profiles from your left over timber, you should have enough in long enough lengths. The overall size of the frame is 870x300mm this is allowing 5mm (2.5mm on each side) which is tight, the reason for this is you want the space between the frame and the door to be very minimal so little temperature and moisture escapes. Once you have cut the pieces to the right thickness you can cut the lengths. Even though the door will have mitered corners it is easier for routing the channels if you keep the ends straight and then miter them after, this way you can see the lines you'll make to line up the cut easier. You might want to add a few millimeters on when cutting the straight cut to allow for the thickness of the miter blade.

Adding the channel

This part is to hold the polycarbonate and smart film panel in place. Using a router table and a router bit that matches the thickness of your panel (remember to calculate the thickness of both the polycarbonate and the film together), this should add up to about 7mm but its best to add a little tolerance anywhere between 0.5mm-1.5mm should be enough. The channel should be about 5mm deep, although when I added the film on to the polycarbonate the section of wiring was visible so I made the top channel deeper by another 4mm. The routed channel should be in the center of the profile, I found the best way to measure this was to add a pencil mark to the section that I needed to cut and line the fence up by eye, doing a test cut first to check the dimensions are correct.

Mitered corners

As mentioned above, the corners for the door are mitered. I used the Festool miter saw for this setting the position to 45 degrees, although you could use a table saw with a 45 degree blade too. Measure the outer length of the cut to match the dimensions of the door (870mm for the height, 300mm for the width). Making the cut on each side should give you the correct size for the door and a neat mitered corner to glue and pin.

Drilling the hole for the wires

The two wires coming from the smart tint panel should be exiting the door frame at the top right hand corner so choose the The diameter of hole you need is 5mm. It is easiest if you drill the hole from the inside so you can line up the center with the center of the channel. Measure where the wires will need to exit (this should be 10mm from the end of the piece but its best to measure yourself) and mark your hole position. Using either a pillar drill or a hand drill make the hole and test the wires fit through.

Adding the mortise

Before putting the frame together you will need to remove a section of the door frame for the hinge which is called a mortise. There are a couple of ways to do this but I found it easier and neater to use the miter saw which has a height setting to stop the blade going all the way down. Firstly, I marked on both the door frame piece (the right one) and the section on the frame that the hinge will be fixed to making sure they line up. Then I marked the size of the hinge, for me this was 50mm but measure your hinge first and use your measurement. Using the miter saw I made a shallow cut (about 2mm deep) along the two outer lines of the hinge I just marked out. Then moving the piece of wood the width of the blade each time to remove the internal section for the hinge which should then sit flush to the wood. You can repeat this process for the main frame, remembering that the internal edge of this piece of timber has an aluminum angle covering it which means you can cut the mortise from edge to edge. If you are using a chisel to remove the wood you can be more precise in relation to where the wood is removed for the hinge.

Putting the frame together

Before you glue anything, make sure the panel fits in the channels you cut by clamping all four pieces together around it. If it doesn't fit you may need to make your channels deeper. When you know it fits you can glue it together, you can start with a long piece and a short piece to make a right angled corner to then slot the panel in, make sure you feed the wires through the hole. Add wood glue to the two ends you start with and hold them in place with clamps. Add the panel into the channel and repeat the gluing and clamping ensuring you are gluing the corners at 90 degrees. When you have the door glued and clamped you can use a brad gun to insert tiny pins to the corners to secure the joints. Leave the door drying for a few hours, or overnight.

The instructions in this step make door mounted sound very easy and in principle it is a simple process but due to working with little tolerances and needing everything to be absolutely 100% straight right angles it can mean you come into some problems. You may have to sand an edge or two or re-drill some holes to get the hanging position correct. The basic principle when using a piano hinge is that the center of the barrel or pin is in line with the edge of the frame and door so that the door is pivoting around the edge rather than around a larger radius which increases unwanted movement of the door.

You should have a door ready to be installed with the mortised sections on both the door and the frame for the hinge.

Firstly check that the door actually fits. You should have clearance of 5mm. As we are working with real wood it is likely that it may have shifted, or at least isn't perfect to the nearest millimeter so its always best to check it all fits first.

Line up where the hinge needs to be on the door part. Using a center punch, mark the center of each hole of the hinge. Using a drill bit that is the correct diameter for the self taping screws you are using (this should be the same diameter of the shaft of the screw between the thread) and drill the holes for the hinge, making sure not to go through to the other side of the wood. Repeat this for both hinges on the door side then you can fix the hinge in place with the self taping screws.

Position the machine on its side with the hinge part facing up, place the door in position, lining up the hinge to the mortise you removed on the frame. You might find it easier to place machine on the edge of the table and a block at the right height on the floor to hold the door in a position where the hinge is flush. Repeat the drilling process and screw the hinge in place with the self tapping screws.

If you need to adjust anything on the door which requires you to remove the screws just be aware that the more you screw in and screw out it will reduce the strength of the thread in the wood.

Door handle

The handle is a simple C shaped pull handle with screw. Measure and mark the position of where the handle will fix to the door then drill holes big enough for the screw to fit through easily. Depending on what type of screw used will determine how to counter sink it. I used a thumb screw so I drilled a larger hole deep enough for the the screw to be flush with the frame.

The machine has been designed to provide a nice growing environment for mycelium which means nice and warm, fairly high humidity and mostly dark. In order for the incubation chamber to control these conditions a control system is needed to tell specific appliances like heat pads to turn on and off at certain times. The system offers 4 changeable appliances; temperature is supplied by 10 heat pads, humidity is supplied by a small humidifier, light is turned on and off with the smart tint on the windows, and the laminar flow is controlled by switching the blower on and off. The two simple controls are the light and the blower which is controlled by a simple on off switch and a relay. The more complicated part of the system is the temperature and the humidity which are both controlled by a thermostat type system where a sensor reads the current temperature or humidity and turns the appliance on or off depending on if the target value is lower or higher than the current value.

Laser cutting the face

The face of the control panel is acrylic which has been laser cut with text to form a grove in the plastic, then spreading acrylic paint into the groves forms the blue text. The holes for the potentiometers need to be the correct diameter for the knobs of the potentiometers you are using, as well as the cut out for the LCD screen needs to be correct to the dimensions of the screen.

Knobs

The knobs are made on the metal lathe, this was a conscious decision so I could learn to use the machine but it not entirely necessary as you can order perfectly suitable knobs online. The knobs were made with 1inch aluminum, faced and turned then using a knurling tool I formed the knurling across the whole length that I would cut down into individual knobs using the parting tool. I then machined a hole on the back side by flipping it around in the colette and facing the surface while I was at it.

The line on the knob is formed on the manual mill, using a chamfer mill to create a channel from the middle to just in from the edge.

In order for the knobs to fix securely onto the potentiometer I used the lathe to custom make a shaft that would fit over the nut and allow me to place a set screw into the shaft of the potentiometer. To do this I turned a cylinder of aluminium down to 20mm and drilled a hole that was big enough to cover the nut fixing the potentiometer in place. I then parted it to be 8mm in length. Using the pillar drill, I drilled a hole that would be enough clearance for the tapping drill which should correspond to an M2.5 set screw. Then using a 2 part epoxy bond the two parts of the knob together and set for a few hours depending on the product you use. When dry, the knobs can be fixed to the potentiometers with an allen key.

The Laminar flow is the device that makes the incubation chamber contamination free (or at least significantly reduced), it includes a high quality HEPA filter and a high powered blower that pushes air through the filter into the incubation chamber. The size of the filter and blower is what has governed the size of the machine so if you get a different filter you will have to adjust the measurements to suit. I ordered my filter and blower from Fungi Perfecti

The filter sits on ledges attached the the side panels beneath the incubation chamber, these should be strips of wood that protrude enough that all four edges of the filter can sit on it which should be about 1inch or 25mm. The positioning of these will be the height of the filter minus the dimension of the oak baton.

The piece of wood that sits in the middle between the filter cavity and the blower space needs to have a hole cut in the place where the air comes out of the blower, measure this out and then using a jigsaw you can cut the hole; its not vital that it is perfectly neat, just as long as the hole is the same size as the hole on the blower. This piece of wood should be thick enough to support the heavy blower, about 3/4 inch ply would be suitable. To fix the blower in place once you have cut the hole you will need to put threaded inserts into the plywood to line up with the holes on the blower, use a centre punch to make sure the hole will line up. By adding the threaded inserts means you can remove the blower if you need to. The tabs that the panel fixes too were cut on the water jet, this is unneccesary as I'm sure you can by pre-made metal tabs with pre-drilled holes. The tabs need to be flat and have holes on one side for the screw that will be permanently fixed to the frame and holes on the other side to line up with threaded inserts that go into the panel which will allow you to take this panel off if you need to.

Panels on open side

Measure and cut the panels on the table saw. I used 1/8 inch ply which leave enough space for the tabs. These are fixed with magnets and steel tabs; you can order the small earth magnets from Mcmaster Carr , with pre-made holes. Drill holes for self tapping screws on the back side of the panels in a triangular position so the panels can't tilt, make sure not to drill the hole way through, and screw in the magnets. The steel tabs can either be bought online or cut from a larger length of steel equal angle into 1/2 inch tabs with a hole on one side to screw into the frame. Place the steel tabs onto the magnets and insert the panel into position, mark where the tabs sit (this doesnt have to be that accurate). While the tabs are not connected to the magnets add a screw through a pre-drilled hole to fix the tabs in place. repeat this for all the panels apart from the top one. This doesn't need magnets as it needs to be able to come off easily by pushing a corner down to lift it up. It can sit on the same tabs without the magnet. Position this panel flush with the wooden cross bars.

The electronics was a challenge because I had little to no experience or understanding of electronics prior to the project, I guess I never listened in science class at school. However, the electronics is a main part of the project being the key to controlling the conditions inside the incubator. The variables that the machine controls are temperature, humidity and light, as well as turning the laminar flow on and off.

The system is controlled by a metro mini, this works the same as an arduino uno but is smaller and has 2 extra pins, all the pins will be needed for all the devices. The metro mini is powered from the micro connector port with a USB cable into a USB wall adapter because when I was testing the power via the Vin pin on the board I was experiencing voltage spikes, this way of powering means it doesn't connect to the pins which doesn't interfere with any of the other devices on the board. All four devices are controlled by their own relay switch. The blower and the smart tint panels are simple on off switches from the control panel, the temperature and humidity are controlled by sensors that read the current state and tell the metro mini to either turn the device on or off depending on the target state set by the user on the control panel.

The temperature comes from a series of heat pads which run off of two 9v power supplies. The heat pads need to be small in order to be hidden between the middle panel that divides the incubator side and the storage side. This void between the two panels is necessary for all the cabling to be invisible as the wires need to run from the top where the control panel is to the bottom where the power supplies are stored. The temperature system is based on a thermostat; the target temperature is set, the current temperature is read from the sensor, the metro mini will tell the relay to turn on the heat pads if the current temperature is lower than the target temperature.

The humidity comes from an electric humidifier that fits between the filter and the next shelf up, I bought one from amazon. The system works the same as the temperature, just like a thermostat; the sensor tells the metro mini what the current state is and the metro mini tells the relay to switch on or off depending on the target humidity value from the potentiometer. The humidifiers you can buy online usually come with an on/off switch to use while the device is still plugged into the mains as well as a few settings that you can switch through. This means that when the relay turns the humidifier off the internal switch is reset and will need to be pressed each time the metro mini tells the relay to turn back on again, which isn't ideal as that requires you to go into the incubation chamber and press the switch your self. In order to stop this you will have to open up the electronics for the humidifier and add another relay to the part where the button is and connect this to a pin on the metro mini, within the code you can tell the relay to be turned on when the main relay is turned on as if it was electronically pushing the on/off button itself.

The sensors for light, temperature and humidity are installed in the center of the middle panel into the incubation chamber, although there may be variations in conditions within the incubator it is assumed that it would regulate itself being such a small space and therefor the middle of the space would be the most average reading.

The LCD screen uses lots of pins and is based on the example from Adafruit, The RGB is set to blue which uses the last connection on the board, the two next to it are red and green so if you want to set a specific colour you would have to use a larger micro controller as all the pins are taken.

The fritzing diagram shows a rough outline of how the wiring works but this is just a guide line.

Coding

The code is set up into functions for each device that go into the loop. The blower and the light functions are straight forward, turning the pin to HIGH when the potentionmeter passes the threshold to ON and LOW when turned the other way. The temperature function is a bit more complicated, it tells the metro mini to take a reading of the target temperature from the potentiometer which has been mapped so that the beginning constraint of the potentiometer starts at the first temperature (20degrees) and the end constraint is the last temperature (30degrees) so that the display on the LCD screen corresponds to the marker on the dial. The sensor is then initiated and a reading is taken, if the sensed temperature is lower than the target temperature the metro mini will tell the relay to turn on, turning on the heat pads on, these will switch off when the sensed temperature matches the target temperature.

The humidity function is even more complicated because the values do not go up in single increments, and the display should correspond to that actual marker so a round reading boolean had to be added which would set parameters of potentiometer values to say particular values, for example 'if ( preciseReading >= 0. && preciseReading <= 85.) {roundReading = 85.;} in other words, if the precise reading from the potentiometer is bigger or equal to 0 and less or equal to 85 then make the reading 85, and the same used for all the variables up to 100.

The sensors all connect to the same pins on the metro mini rather than having to have individual pins for the SDA and SCL connections for each sensor. All the libraries for the sensors are included at the top of the code. The code for each sensor has been taken from the Adafruit test : light, temperature, humidity

The code for the LCD screen has been put together within each function to tell the LCD screen to display the state of each device and for the temperature and humidity it displays the target and the current state. The code has been written to move between each screen every few seconds but when one of the potentiometer values changes it switches immediately to that screen. This works on a 'millis' function with each device having its own screen ID that it switches to.

Once all the other parts have been worked out and installed it makes sense to start gluing the frame bit by bit. It has to be done in a certain way as the window panels need to slide into the grooves on the incubator side.

You can start by gluing the right hand side of the frame, remembering that you need to slide the polycarbonate panel into half way through. It is best to start with gluing the top cross bar to the two rights and then sliding the panel into the channel. Make sure you glue the wooden pieces in the correct orientation which should be clear from where you marked the line for the domino and they should only fit in one way anyway. once the panel is in it's a bit of a wiggle to get the next piece in that sits below the panel as you don't want to pull the top piece out of the holes. Another way to do this would be to glue the cross bars to one of the uprights and flex the top piece enough that the polycarbonate panel can fit in the groove and then fix the second upright into the dominos. Clamp all joints and leave to dry for 12 hours.

Next is the back polycarbonate panel, by gluing the top cross bar in place allows you to slot the panel in place while you glue the middle and bottom cross bars. This will leave you with the back right corner. Clamp all new joints and leave to dry for 12 hours.

Next place and glue the front pieces where the door will sit which is in place of the polycarbonate panel. Clamp all new joints and leave to dry for 12 hours.

Then the middle piece which is a little tricky as you have to slide the middle panel which has pre-cut holes for the sensors to fit into, as the other pieces are glued you don't want to open out the joints too far as this will break them so you will need to use short domino pieces that allow you to open it up just enough to fit the cross bars in. Clamp all new joints and leave to dry for 12 hours. Now you should have the whole incubation chamber frame glued.

The next part is much easier, the open side can be glued all in one go. Fix the left hand side together with glue then add the cross bars. Clamp all joints and leave to dry for 12 hours. Then you can add glue to the joints and fix the open side to the incubation chamber frame. Clamp all joints and leave to dry for 12 hours.

The frame should be ready.

Now you have the frame put together you will want to add the base so you can move it around easily.

The base is a 3/4 inch ply board with four casters that swivel and lock. The board is fixed to the bottom of the frame with threaded inserts so it can be removed. It is necessary for it to be removable as you may need to access the filter and blower sections and as the bottom panels are fixed with hidden fixings you will only be able to access them from the bottom. The ply board is 1/2 inch smaller than the footprint of the machine so that you won't see it unless you duck down to the floor.

Mark out the positions for the threaded inserts on the base, you will need three along the long sides and 1 on the short sides. Drill these holes larger that the bolt you will need for the threaded insert. Then line up the board on the base of the frame and mark the center of these holes with a center punch. These will be close to the edge of the wood so make sure the board is equal distance from each side. Use a hand drill to make the holes in the frame for the inserts, making sure you don't go further than you need. Glue in the threaded insert.

Then you can fix the casters in place by lining them up far enough in from the edge of the board that they clear the frame. Drill holes for the bolts and fix in place with washers and nuts.

The perforated shelves are there to place growing items on while still allowing air to flow through and out the top providing suitable air flow for the mycelium to grow. Therefore the perforation has been designed so enough air and humidity can pass through the whole incubator, if you were to reduce the amount or size of holes this would limit their functionality.

The shelves were cut on the water jet cutter, a high pressure water CNC machine that can cut through almost anything. I used 3.5mm thick aluminium so that the shelf would still retain its rigidity after the perforation. The holes are 6mm in diameter and make up about 80% of the surface area meaning that only 20% of material is left.

When generating the tool path for the cut it was important to ensure that kerf of the cut was on the internal diameter of each circle as the Omax Layout software had a tendency to create toolpaths that were cutting on the outer edge of the circles.

The cut takes 2.5 hours per panel but by reducing the thickness of the material in the settings by a small amount it may reduce the cutting time.

Now, you should have everything together. It should be working as expected but you may need to do a few tests. The final touches are to sand the frame and to apply a lacquer to stop the wood being affected by any moisture from the humidifier and to also give it a nice finish.

Sanding

Using a electric hand sander you can neaten the joints by sanding them flush to each other as it is likely they may have shifted from the movement of the wood. Using sand paper with your hands you can soften the edges of the timber by sanding away the sharp corner, using the electric hand sander may be too strong and you could dent the neat edge.

Lacquer

I used Bio-shield as it is 'especially recommend it for high-moisture and high-traffic areas such as baths and kitchens. As one of our most durable oils, it is suitable for hardwood and softwood floors. Specifications: This product becomes a clear to slightly amber breathable and elastic coating with superior water-resistant characteristics. It will enhance the grain of any wood and is an economical product because of its coverage characteristics.' which was exactly what is needed. I taped up the window panels so I wouldn't drip down.

Apply one coat, leave for 15 minutes then wipe down to remove excess, leave to dry for 12 hours. Repeat, 2-3 times.

You are ready to grow.

Lets grow the whole world out of mycelium and save the planet!