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AmigaNut
Stranger
Registered: 10/30/02
Posts: 5
Last seen: 21 years, 11 months
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Advanced Terrarium/Humidifier
#1008517 - 10/30/02 11:43 PM (22 years, 3 months ago) |
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Greetings,
I have come up with an idea for an advanced combonation incubator/terrarium that regulates accurately rH and temperature as well as providing circulation. The idea is in its infancy but I am currently collecting the components needed to build such a "dream machine."
Currently, I grow uhhh edible mushrooms in a closet. Knowing that some people might see these mushrooms and think the wrong thing, I want to grow them hidden from view in an automated system. The place I have staked out is in a hidden enclosure without HVAC (heating, ventilation and air conditioning). This means that the temperature variations can be extreme during the day & night. To provide heating and cooling, respectively, to the incubator and terrarium, I plan on using a thermoelectric "heat pump." A thermoelectric heat pump is a solid-state device that when a DC current is applied to it will get hot on one side and cold on the other. By attaching large heatsinks and moving air through the fins of the heatsink, you get a device that will heat the air on one side and cool on the other. Because these devices do not work well in humid conditions, the proper application will be to heat/cool a smaller air space and then move this air into the incubator/terrarium. In essence, the system will fill a smaller cotainer with fresh, filtered air and remove heat from the one side and pump it to the other side. However, left to run continiuously will get you a situation where one side drops to refregerator temperatures and the other to >150 F temperatures. For this I will use a DS1620 IC (a $6 digital thermometer chip with a serial interface) in the incubator and terrarium. The thermometers will be attached to a M68HC12 microcontroller that will turn the thermoeletric device on/off and run the fans as needed. Another case is when you want to hear or cool one side and not the other. In this case, the opposite side will vent the uneeded air through the exhaust.
Humidity is handeled seperately by recycling the air within the grow environment through a cool mist humidifier. The humidity is checked with a digital rH meter attached to the same microcontroller. I am planning on using a humidity probe ($15) the changes its capiticitance in response to humidity changes. The capacitance is used to generate an oscillation that is compared with a known oscillation frequency. The microcontroller calculates the difference in frequency and gets the rH value.
Here is a diagram of the system to help people visualize it:
A word about cost. The most expensive piece of equipment is the thermoelectric device. The chip itself is cheap, around $20. The large heat sinks are also about $20-40 each. Making the two sides thermly isolated is a little more tricky. I will probably wuss out and go the premanufactured route. I?ve setteled on AHP-150FF which I estimate can keep a terrarium at a smooth 70 degrees in 97 degree weather and keep an incubator at 80 degrees in freezing weather. The cost is a real killer. I was quoted $360 for the unit. I was originally planning on using two, one for the incubator and one for the terrarium but at that price I decided I should make the most out of the single unit.
With a microcontroller, the unit should even be smart enough to heat or cool both sides if needed. A thermoelectric device will pump heat in the opposite direction if the voltage is reversed. That means I can heat/cool up one side and blow the air in and then do the same to the other side and blow it in. Alternatively, I can just link the two sides with a bi-directional (i.e. 2 fans) fan and just heat/cool and pump the air into both terrariums. This will require experimentation.
Anyway, the reason I?m sharing all this is to see if there?s any interest for others to buy such a system. The costs are substational, at least $500, just for parts, for a thermoelectric system to control two 4?x4?x2? environments. The thermoelectric system can be scaled up for larger grow environments with a corresponding increase in price. This is all based on theorertical calculations. I would not ask for money until I have my own system up and running and that is probably months and months away.
Of course, I will also except constructive criticism and ideas. The design of such a system is within my capcabilities. I?m en eletrical engineer, I?ve built robots for fun and I do this sort of electronic stuff for a living. I?m just trying to build a system that requires minimal maintanence and can run is "mushroom-unfriendly" environment.
This is a variation and imporvement of what I was doing earlier this summer where tempeartures regularly reached >100 F around the terrarium. I have a thermoelectric cooler (those battery powered coolers you see are all thermoelectric) sitting next to the terrarium and using a timer, I regularly replaced the air in the terrarium with the air the cooler, which would then be recycled through a humidifier. The system is good and it works but it requires constant readjustment of the timing through the use of portable rH/Temperature reader that sits in the terrarium. My goal is to automate that system.
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Anno
Experimenter



Registered: 06/17/99
Posts: 24,168
Loc: my room
Last seen: 10 days, 12 hours
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Re: Advanced Terrarium/Humidifier [Re: AmigaNut]
#1008642 - 10/31/02 12:16 AM (22 years, 3 months ago) |
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Overall a good idea, 2 points i noticed though I don?t like:
>by recycling the air within the grow environment through a cool mist humidifier. The main task of a humidifier is to provide moist FRESH air, to displace the CO2 that is emitted by the mycelium.
And, second, the incubator doesn?t need additional humidification, except the relative humidity is 30% or lower.
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AmigaNut
Stranger
Registered: 10/30/02
Posts: 5
Last seen: 21 years, 11 months
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Re: Advanced Terrarium/Humidifier [Re: Anno]
#1008671 - 10/31/02 12:24 AM (22 years, 3 months ago) |
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Thermoelectric systems are not meant to be used in a humid environment. Condesation collects on the heat sinks and lowers the effeciency. Enough water collects and you don't have good air circulation. That's why (hopefully) dry air will be pulled from ambient environment, cooled/heated and deposited into the grow environment. If the system is working hard to heat/cool the air then the system will be venting air more often then is needed for proper air exchange. It is very likely the enivornment will get too dry without the humidfiers, speaking from my previous expierence with a thermoelectric coolant system.
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AmigaNut
Stranger
Registered: 10/30/02
Posts: 5
Last seen: 21 years, 11 months
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Re: Advanced Terrarium/Humidifier [Re: AmigaNut]
#1008687 - 10/31/02 12:29 AM (22 years, 3 months ago) |
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Anno,
Wanted to add that CO2/venting is handeled separetly from humidification. However, to take your advice, I could vent the temperature-treated air through the humidifier and into the grow enivornment. The reason I'm keeping them spearate is for when I want to humidify but not change the temperature of the environment. Also, I'm surprised at the low number of 30% you quote. I typically freak when the rH drops below 50-60. I try to maintain an 80-90% rH environment for casings.
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Anno
Experimenter



Registered: 06/17/99
Posts: 24,168
Loc: my room
Last seen: 10 days, 12 hours
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Re: Advanced Terrarium/Humidifier [Re: AmigaNut]
#1008713 - 10/31/02 12:40 AM (22 years, 3 months ago) |
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>I try to maintain an 80-90% rH environment for casings. For incubating them? They are covered, alright? So why the high humidity?
30% is not the optimum for incubation(that would be more like 60-70), don?t get me wrong, but it can be tolerated in small scale cultivation.
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AmigaNut
Stranger
Registered: 10/30/02
Posts: 5
Last seen: 21 years, 11 months
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Re: Advanced Terrarium/Humidifier [Re: Anno]
#1008747 - 10/31/02 12:54 AM (22 years, 3 months ago) |
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I keep the humidity high for both incubation and fruiting. I incubate in 1/2 pint jars with wide-mouth (90mm) lids. The lids are replaced with filter discs for better air exchange. I find that the top of the substrate gets bone-dry by the time they are birthed/caked unless I keep the humidity up high (they're still dry, just less so). It seems you think that lower humidity for fruiting is the way to go. I'll attempt to lower it in my current system (easier said than done). New system you'll be able to connect to the microconrtoller through a serial connection and tell it "keep humidity at 55%" and it'll do its best. What's "best" will of-course need to be worked out in hardware in software.
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Anno
Experimenter



Registered: 06/17/99
Posts: 24,168
Loc: my room
Last seen: 10 days, 12 hours
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Re: Advanced Terrarium/Humidifier [Re: AmigaNut]
#1008769 - 10/31/02 01:03 AM (22 years, 3 months ago) |
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>It seems you think that lower humidity for fruiting is the way to go.
No, no, no... Not for fruiting, for INCUBATION. For fruiting you want to be in the 90-100% range.
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AmigaNut
Stranger
Registered: 10/30/02
Posts: 5
Last seen: 21 years, 11 months
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Re: Advanced Terrarium/Humidifier [Re: Anno]
#1008852 - 10/31/02 01:30 AM (22 years, 3 months ago) |
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OK! I understand what you're saying now! I am no longer confused. This system will allow different humidity values for the terrarium and incubator.
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zeta
Stranger

Registered: 05/24/02
Posts: 3,972
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Re: Advanced Terrarium/Humidifier [Re: AmigaNut]
#1009128 - 10/31/02 03:53 AM (22 years, 3 months ago) |
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A filter disc as a lid provides far too much gas exchange, you want to put a lid with a 1/2" hole over the filter.
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Raadt
nicht

Registered: 06/07/02
Posts: 2,107
Loc: azurescending
Last seen: 5 years, 9 months
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Re: Advanced Terrarium/Humidifier [Re: zeta]
#1009870 - 10/31/02 10:47 AM (22 years, 3 months ago) |
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Zeta, are you speaking of incubation? or fruiting?
-------------------- Raadt
-- The information I provide is only information from readings, growing of gourmet mushrooms, and second hand stories--
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Anno
Experimenter



Registered: 06/17/99
Posts: 24,168
Loc: my room
Last seen: 10 days, 12 hours
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Re: Advanced Terrarium/Humidifier [Re: Raadt]
#1009883 - 10/31/02 10:55 AM (22 years, 3 months ago) |
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Colonisation.
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