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- #41
cbdhemp808
Well-Known Member
Made some progress. Hoping to complete the dehum/sensor box tomorrow, Thurs.
Turning a small chest freezer into a cool & quick bud dryer
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cbdhemp808
Well-Known Member
Coming together...
Here's a photo showing the boards that make up the dehum/sensor box. The box was designed using 3-D CAD software. The fan is positioned at the top of the board that separates the inflow chamber (where the dehum is) from the outflow chamber (where some cooling will occur). The fan helps move air from the dehum side to the outflow side. Moist, cooler air flows into the box, and dryer, warmer air flows out. The temperature and humidity sensors will be placed on the outside of the box, facing the bud drying racks, and near the top of the box where the air will be generally more damp and warm. This makes sense, because we want the dehum to remain running, and the fridge to remain running, until the potentially most humid and warmer zone is settled back to the temperature and humidity set points. The box serves to separate the air-drying process from the ambient temp. and RH of the bud drying zone.
I see the system as working in pulses (or cycles). As the temperature passively warms, the buds will emit more moisture, and the dehum will turn on. This in turn will cause more warming and more evaporation. Then the temp. controller will turn the fridge on. When RH settles back to 54%, the dehum goes off. And when the temp. settles back to a degree below the set point (64° or 68°), the fridge will go off. It will be very interesting to find out the duration of this idle period, and I'm guessing the period will change over the entire course of the drying, becoming longer. I'm also guessing that the period will be shorter during the first 3 days of drying, when the temp. is set at 68°.
Nine pine boards that will make the dehum/sensor box... ready for screws. I'm making sealant for the wood out of beeswax, coconut oil, and food-grade orange oil and pinene. Finished box dimensions: 15-3/4" x 8" x 16". The box is designed to accommodate a dehum upgrade if needed—a slightly bigger and more powerful mini-dehum. The box will also have four 3/8" tall wooden feet, made from the plugs saved from the 1-1/8" dia. holes cut for the air inflow and outflow.
Here's a photo showing the boards that make up the dehum/sensor box. The box was designed using 3-D CAD software. The fan is positioned at the top of the board that separates the inflow chamber (where the dehum is) from the outflow chamber (where some cooling will occur). The fan helps move air from the dehum side to the outflow side. Moist, cooler air flows into the box, and dryer, warmer air flows out. The temperature and humidity sensors will be placed on the outside of the box, facing the bud drying racks, and near the top of the box where the air will be generally more damp and warm. This makes sense, because we want the dehum to remain running, and the fridge to remain running, until the potentially most humid and warmer zone is settled back to the temperature and humidity set points. The box serves to separate the air-drying process from the ambient temp. and RH of the bud drying zone.
I see the system as working in pulses (or cycles). As the temperature passively warms, the buds will emit more moisture, and the dehum will turn on. This in turn will cause more warming and more evaporation. Then the temp. controller will turn the fridge on. When RH settles back to 54%, the dehum goes off. And when the temp. settles back to a degree below the set point (64° or 68°), the fridge will go off. It will be very interesting to find out the duration of this idle period, and I'm guessing the period will change over the entire course of the drying, becoming longer. I'm also guessing that the period will be shorter during the first 3 days of drying, when the temp. is set at 68°.
Nine pine boards that will make the dehum/sensor box... ready for screws. I'm making sealant for the wood out of beeswax, coconut oil, and food-grade orange oil and pinene. Finished box dimensions: 15-3/4" x 8" x 16". The box is designed to accommodate a dehum upgrade if needed—a slightly bigger and more powerful mini-dehum. The box will also have four 3/8" tall wooden feet, made from the plugs saved from the 1-1/8" dia. holes cut for the air inflow and outflow.
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- #43
cbdhemp808
Well-Known Member
The dehum/sensor box is assembled!
The assembly went fairly well, considering I made all the cuts with a skill saw (except for the cut-out for the fan). All the seams were fairly tight, except for the lid where I had to use some sticky-back felt strips to help make the seal. Eventually I may use some other material for the seal. For now the lid is held on with 6 screws. Eventually it will be hinged and held tight with a chest latch. I haven't applied the beeswax/oil wood treatment yet. I also haven't put the 4 wooden feet on yet.
View of the dehum/sensor box inside the chest freezer. Air intake holes on the left, air outflow holes on the right. Mini-dehum power cord on the left, air circulation fan power cord on the right. For now I am just running the cords through the air intake holes, but later there will be two holes on the backside of the box for the cords, sealed w/ silicone. The remaining space in the fridge is where the custom bud drying rack system will go. The rack system will have 8 racks held in a wooden frame made of redwood. Individual racks will also have redwood frames, and will use stainless steel mesh. Notice the intake and outflow holes are positioned about half-way vertically in the bud drying space.
Top view with lid removed, looking down at the mini-dehumidifier and 3-liter bottle for cold thermal mass. The airflow fan is flush mounted at the top of the center board for easy access and removal, and held tight in place by friction fit. Here you can see the black felt I used as a gasket for the lid, to make a better seal.
A closer look at the mini-dehum. It's positioned next to the intake holes which provide air directly to the dehum's fan-powered intake. The dehumidified air comes out the top grill. You can see the power cord is routed around the back. Eventually the cord will come through the back wall of the box, directly opposite the power socket on the device.
What's that mysterious green glow?
The Pohl•Schmitt mini dehumidifier.
More and next steps...
The assembly went fairly well, considering I made all the cuts with a skill saw (except for the cut-out for the fan). All the seams were fairly tight, except for the lid where I had to use some sticky-back felt strips to help make the seal. Eventually I may use some other material for the seal. For now the lid is held on with 6 screws. Eventually it will be hinged and held tight with a chest latch. I haven't applied the beeswax/oil wood treatment yet. I also haven't put the 4 wooden feet on yet.
View of the dehum/sensor box inside the chest freezer. Air intake holes on the left, air outflow holes on the right. Mini-dehum power cord on the left, air circulation fan power cord on the right. For now I am just running the cords through the air intake holes, but later there will be two holes on the backside of the box for the cords, sealed w/ silicone. The remaining space in the fridge is where the custom bud drying rack system will go. The rack system will have 8 racks held in a wooden frame made of redwood. Individual racks will also have redwood frames, and will use stainless steel mesh. Notice the intake and outflow holes are positioned about half-way vertically in the bud drying space.
Top view with lid removed, looking down at the mini-dehumidifier and 3-liter bottle for cold thermal mass. The airflow fan is flush mounted at the top of the center board for easy access and removal, and held tight in place by friction fit. Here you can see the black felt I used as a gasket for the lid, to make a better seal.
A closer look at the mini-dehum. It's positioned next to the intake holes which provide air directly to the dehum's fan-powered intake. The dehumidified air comes out the top grill. You can see the power cord is routed around the back. Eventually the cord will come through the back wall of the box, directly opposite the power socket on the device.
What's that mysterious green glow?
The Pohl•Schmitt mini dehumidifier.
More and next steps...
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- #44
cbdhemp808
Well-Known Member
Some more comments about the system...
I'd like to explain a bit more here about the air flow design. After my initial testing of both the temperature and humidity control, I intuitively felt that there should be a "baffle" so that the sensors are picking up a more representative sample of the air. I gave this a lot of thought over time and the baffle concept turned into a "directed airflow" design in my mind. I did some sketches and thought about it quite a bit, keeping also in mind the requirement for low energy consumption (due to my limited off-grid solar power). I decided on holes, and then specifically 4 holes, because I intuitively wanted some pressure behind the outflow, so that the drier air would penetrate into the drying racks, away from the sensors, and mix with the air in the rack system. Notice that the intake and outflow holes are positioned about half-way vertically in the bud drying space. This is to encourage more air mixing. (One construction note... I will probably use some clear aquarium-grade silicone on the seams inside the box, to make the compartments airtight, except for the intake and outflow holes. This is a fine point, but it will slightly improve the pressure in the outflow side, and reduce possible unwanted mixing in the intake side.)
The below photo is during a test with both the dehum and fan running. I wanted to get a feel for the air pressure of the outflow. I also tested the intake pressure using a strip of paper towel—it readily stuck to the holes.
As I mentioned before, the humidity and temp. sensors will be placed on the left side toward the top. I see them located probably between the knot and the top edge below the lid. I think the air circulating here will be generally more damp and a little warmer than areas lower down. Why? Because warmer air rises, and damper air also rises. But the gentle air currents from the intake and outflow holes will also create mixing, which is good.
The completion of the dehum/sensor box is a big step forward for this project; however, there's still many more steps to go. My next step is to prepare for a lid-closed live test, with both the temp. control and humidity control active. This time, I'll set up one or two more cable glands so that the sensor probe cables can be routed through the fridge lid. The humidity probe cable will need some work, because the sensor won't fit through the cable gland, so I'll need to add a "pluggable union"...
The sensors will then be mounted to their position on the box. For this next test, I'll probably also just leave the power cables going through the air intake holes in the box.
The test will be the first one with the temperature down to 68°F and with the dehum also running to bring the RH down to 55%. After that test, I'll run another one with the temp. down to 64°F.
Before the test I'll also build an equipment panel on the wall behind the fridge, using a piece of plywood. On the panel I'll mount: a power strip, both Inkbird controllers, and the USB 5v-to-12v converter (for the fan). Everything will be plugged into the power strip, which will be powered by an extension cord. This will enable me to add a power monitor between the power strip and extension cord, in order to monitor the whole system's power usage over time...
I'd like to explain a bit more here about the air flow design. After my initial testing of both the temperature and humidity control, I intuitively felt that there should be a "baffle" so that the sensors are picking up a more representative sample of the air. I gave this a lot of thought over time and the baffle concept turned into a "directed airflow" design in my mind. I did some sketches and thought about it quite a bit, keeping also in mind the requirement for low energy consumption (due to my limited off-grid solar power). I decided on holes, and then specifically 4 holes, because I intuitively wanted some pressure behind the outflow, so that the drier air would penetrate into the drying racks, away from the sensors, and mix with the air in the rack system. Notice that the intake and outflow holes are positioned about half-way vertically in the bud drying space. This is to encourage more air mixing. (One construction note... I will probably use some clear aquarium-grade silicone on the seams inside the box, to make the compartments airtight, except for the intake and outflow holes. This is a fine point, but it will slightly improve the pressure in the outflow side, and reduce possible unwanted mixing in the intake side.)
The below photo is during a test with both the dehum and fan running. I wanted to get a feel for the air pressure of the outflow. I also tested the intake pressure using a strip of paper towel—it readily stuck to the holes.
As I mentioned before, the humidity and temp. sensors will be placed on the left side toward the top. I see them located probably between the knot and the top edge below the lid. I think the air circulating here will be generally more damp and a little warmer than areas lower down. Why? Because warmer air rises, and damper air also rises. But the gentle air currents from the intake and outflow holes will also create mixing, which is good.
The completion of the dehum/sensor box is a big step forward for this project; however, there's still many more steps to go. My next step is to prepare for a lid-closed live test, with both the temp. control and humidity control active. This time, I'll set up one or two more cable glands so that the sensor probe cables can be routed through the fridge lid. The humidity probe cable will need some work, because the sensor won't fit through the cable gland, so I'll need to add a "pluggable union"...
The sensors will then be mounted to their position on the box. For this next test, I'll probably also just leave the power cables going through the air intake holes in the box.
The test will be the first one with the temperature down to 68°F and with the dehum also running to bring the RH down to 55%. After that test, I'll run another one with the temp. down to 64°F.
Before the test I'll also build an equipment panel on the wall behind the fridge, using a piece of plywood. On the panel I'll mount: a power strip, both Inkbird controllers, and the USB 5v-to-12v converter (for the fan). Everything will be plugged into the power strip, which will be powered by an extension cord. This will enable me to add a power monitor between the power strip and extension cord, in order to monitor the whole system's power usage over time...
Wow. Pretty well thought through. 
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- #46
cbdhemp808
Well-Known Member
Not much to update at the moment, but I'm making a couple corrections in the design...
Thinking about this again, I'm going to place the temp. sensor inside the air outflow chamber of the dehum/sensor box. The purpose is to have the fridge turn on as soon as a rise in temperature is detected due to the dehum going on (the dry air coming out of the dehum is slightly warm). Another way to say this... this location is the warmest location in the system, because of the dehum output. When the dehum isn't running, this location receives a mixture of the air in the drying chamber, due to the fan continually running inside the dehum/sensor box.
The other change is that I'm not going to use aquarium-safe silicon to make the seams (wood/wood) inside the box air tight. Instead I'm going to use melted beeswax. The reason for this change is to make the seam sealant compatible with the wax/oil mixture that I'm going to seal all the wood with... beeswax, coconut oil, and food-grade orange oil and pinene. I've got all these ingredients on hand now.
I'm hoping to do more work on the project this weekend.
Thinking about this again, I'm going to place the temp. sensor inside the air outflow chamber of the dehum/sensor box. The purpose is to have the fridge turn on as soon as a rise in temperature is detected due to the dehum going on (the dry air coming out of the dehum is slightly warm). Another way to say this... this location is the warmest location in the system, because of the dehum output. When the dehum isn't running, this location receives a mixture of the air in the drying chamber, due to the fan continually running inside the dehum/sensor box.
The other change is that I'm not going to use aquarium-safe silicon to make the seams (wood/wood) inside the box air tight. Instead I'm going to use melted beeswax. The reason for this change is to make the seam sealant compatible with the wax/oil mixture that I'm going to seal all the wood with... beeswax, coconut oil, and food-grade orange oil and pinene. I've got all these ingredients on hand now.
I'm hoping to do more work on the project this weekend.
