This simple project is an answer to our need here in Jeju island where we live to dry things mostly foods like mushrooms, herbs, fruits and algae when the weather is bad and sun is not around to help out (and during the rainy season when the humidity is incredibly high so everything goes moldy).
Because of my basic electronic skills the prototype is extremely simple and because of our tight budget very cheap. To summarize the basic idea: we use the heat source to warm up the air which naturally rises up and passes through the things which we desire to dry. To make this happen we decided to use a plywood wardrobe box as a chamber, standard 100 W light bulbs as a heat source, computer fan for removing the warm air later on from the box (connected to the appropriate traffo), usual electric switch and standard electric wires to wire it up, connecting it to the 220 V network and for the testing cheap hang out plastic drier. It is all very primitive, which was the goal so I think anyone can do it.
Now bit more in detail what we used and how we did it.
3x light bulbs (100 W each)
3x light bulb sockets
2-3 m of electric wires (strong enough to carry +- 500 W)
1x electric switch
1x electric plug
1x tin solder
extension cord – sockets
1x soldering iron
1x plier cutter
1x electric drill
- How the electronic part was done
The light bulb sockets had a loop wire attached to them, I’ve cut it in the middle, exposed the copper wire and twisted it around itself so it was consistent/compact. I cut the electric wire which I had extra (designed for heavy electric loads) and used each single core wire, unstripping it and attaching it to the bulb wire, keeping the colours same, to avoid the short circuit. When the wires were twisted around each other I’ve applied large quantities of solder on them to avoid separation later on and taped/covered each of this junctions by large amount of electric tape to insulate it properly. Once all the wires were attached to the light bulb sockets I’ve attached the wire which was to deliver the power in the middle section (close to the middle light bulb), again removing the insulation from it, twisting it around each other, applying solder and insulating it with the tape later on. In this case the power plug was already installed at the end of the wire. I’ve later on cut the power wire again, installing the electric switch, connecting the wires properly to it ???. When this was done I’ve screwed the light bulbs into the sockets and switch them on and off using the electric switch, making sure that all parts function.
The last part of the heat source setup was to make it stable. I’ve cut around 50 cm long 2×2 wooden bar and attached the light bulb apparatus to it, using partly stripped copper wires to make it tight (twisting the stripped part around each other) also drilling holes in the wood, one next to each light bulb, using second set of wires through it to stabilize the bulbs even more. It is not the best solution but it worked.
The ventilator was taken from a computer box and it is a usual computer fan. I’ve used 9 V traffo (power source, check picture) as a power source, again cutting the power cord and connecting the wires, testing before soldering if it works, soldering and insulating them later on. I’ve connected the traffo into the 220V power line making sure that the fan works fine.
- Re-build of the box
2x wooden screws
1x electric drill
The plywood wardrobe was falling a bit apart but as a temporary solution it was sufficient. I’ve measured roughly and labeled by pencil where I want to make holes to allow the air into the chamber, plus the hole on the top of the box to install the fan taking the air out to complete the circulation. To make the holes I’ve used electric drill, drilling many holes around the diameter of the main hole and after that using the hammer I’ve knocked the plywood piece out, making it smoother later on with chisel. This I repeated for all four holes. I’ve installed the fan to the top hole in the box. I’ve drilled in two screws to the side of the box so I could hang out the drier on them.
- Did it worked out?
Well the testing looks good so far. We’ve used a kombucha SCOBY which is a microcellulose fiber to see how quickly it is going to dry out. Starting weight was 286 g (7/11/2013), within 24 hours from switching the 3×100 W and fan on it went down to 145 g (8/11/2013), 53 g (48 hours, 9/11/2013) and 13 g after 72 hours (10/11/2013), when I finished the experiment. The structure of the SCOBY did not dried as I liked but that is not relevant in this case. The drier was running in 3×3 meter room, where we also installed the dehydrator, so the humidity of the air in the room was quite low, temperature between 23-26°C most of the time.
- Things to improve
- the box should be made more sturdy because now it is unstable, alternatively whole new box should be constructed
- the heating element is not very stable, the light bulbs tend to slide on a side touching sometimes the plywood which is dangerous because they are quite hot, they need to be further stabilized
- temperature probe should be installed to monitor the temperature in the chamber, if possible connected to the microcontroller which would allow for switching the heat source on and off depending on the temperature in the chamber – for example switching off one or two light bulbs from the three
- drying racks should be constructed so the space in the chamber can be used more efficiently and also more appropriately based on what is suppose to be dried
- whole box should be made impermeable for the insect so especially the fruit flies can not get in spoiling the fruits or kombucha SCOBY’s with their larvas
- 3D model of the dryer should be made and posted to the blog
- electric circuit should be made as a scheme and posted to the blog
- if microcontroller is used later on, code should be uploaded and shared
light bulb based dryer – nice video which inspired me