I need to build a microbiological incubator, but I am finding some troubles that I ask you guys for help.
I live in a fairly hot place, so I need a heating AND a cooling system on this incubator, and so far, my best idea was peltier modules for both, being controlled separately by two thermostats (as I am not very versated in electronic and programming, I couldn't think of a way of one controlling both).
How would you guys do it? The colling and heating part as well as the temperature controller. I need some sugestions.
Incandescent light bulbs are not an option because when exposed to light, bacteria and fungus can have weird growing patterns.
>>987575
hi mushroom bro. yes a 50w peltier will give you a good couple of degree range for incubating agar plates. you will need air exchange though. what sort of max temperatures do you get inside your house?
>>987575
Ideally what you do is site your chamber in a room that is already environmentally controlled so that there is very little fluctuation. Air conditioning will typically aim for a set temperature and heat or cool as necessary. If you set the room a little colder than you need it will give you headroom to add heat which is much easier than removing heat.
Insulation is important, it acts as a low pass filter for heat, if you have enough insulation your chamber will sit at the average temperature of outside.
Most heat sources produce energy in other forms, typically light for electric or burners but you can shield the light with metal which will reflect or absorb(paint it black) the light and emit it as heat.
>>987578
I never worked with them, to be honest. In fact, I plan to make a kind of a big incubator, so I can frutificate mushrooms inside too, besides the agar plates (just a idea so far). Here it can easily reach 36°C on a hot summers day. Maybe 3 to 4 peltiers would do the work.
>>987581
Ideally, I agree with you. But I don't have any kind of environmentally controlled room, sadly. The insulation part I think I got covered, but we'll see in the future. The light shield is a great idea. Thank you.
Oh, and I just found I can in fact control both sources with one controller. I just have to buy the right one.
>>987584
incubating them is best for rapid growth. but if this is your first couple of tries you're going too expensive. i do everything in open air, use no incubators or flowhoods or anything like that.
as long as it doesnt get below freezing inside, where the mushrooms are, it will be fine. and this is kind of hard to do because the mushrooms generate heat.
now mushroom mycellia dies at 41 degrees. but if you keep them in a cool cupboard somwhere they wont die. they slow down their metabolism exponentially as they aproach this point so all getting too hot or cold will do is slow down their growth. when i lived in a cold climate I just kept them in an eski and fanned once a day with an aquarium heater.
the mycellia doesnt need to be kept in the dark though. intense amounts of UV or extremely bright intense light will cause mutations though.
but even with extremely hot days that get above 41 degrees they can survive because it's just a temporary maximum and inside your house shouldnt get that hot.
>>987575
>I need to build a microbiological incubator, but I am finding some troubles that I ask you guys for help.
>I live in a fairly hot place, so I need a heating AND a cooling system on this incubator, and so far, my best idea was peltier modules for both, being controlled separately by two thermostats (as I am not very versated in electronic and programming, I couldn't think of a way of one controlling both).
:O
I am shocked, shocked I say--
it's a rare event that somebody asks about using Peltiers for something that they are actually suitable for
~~~~~~~~~
a circuit that can apply power "both ways" is called an H-bridge circuit:
https://en.wikipedia.org/wiki/H_bridge
there are chips you can get that are custom-made for doing exactly this. The circuits to support them are not complicated or expensive.
>>987584
>Oh, and I just found I can in fact control both sources with one controller. I just have to buy the right one.
A regular $2 chinese arduino clone can do this. A tmp36 will work for the temperature sensor.
You may be able to just use a regular DC motor controller as well. There are 90v 15A drivers on aliexpress for $8, but I am not 100% certain that you can run a choppy current into a Peltier. You'd have to search online and see if other people are using DC PWM controllers on Peltiers or not....
>>987615
No no, sorry. When I said "I never worked with them, to be honest", I was talking about the Peltiers. I am a bioengineer, and right now I work on a microbiological research lab, so I have a fairly good background on this subject. I'm just too poor to buy a proper incubator. My plan is to give a try in breeding new strains, because I don't have anything good to do with my life on weekends.
>>987696
>>987701
Well, thanks! I'll take a look at this thing. Maybe your approaches are better. My idea was just... buy a shit like this and voila:
http://www.ebay.com/itm/Digital-STC-1000-All-Purpose-Temperature-Controller-Thermostat-With-Sensor-220V-/351575072559?hash=item51db81df2f:g:A~gAAOSwhcJWQVLA
Also, do you think that the Peltiers are really the best solution? It will be something around 0,125m3 to 0,512m3 (the inside, I mean), and will be put in temperatures from 21°C to 43°C at a maximum (for some thermophile bacteria, who knows).
Thank you all, guys
>>987724
>Well, thanks! I'll take a look at this thing. Maybe your approaches are better. My idea was just... buy a shit like this and voila:
>http://www.ebay.com/itm/Digital-STC-1000-All-Purpose-Temperature-Controller-Thermostat-With-Sensor-220V-/351575072559?hash=item51db81df2f:g:A~gAAOSwhcJWQVLA
This would work too, it depends on how much of it you want to DIY.
You would still probably not be able to just hook the Peltiers directly up to that thing tho--since Peltiers draw a LOT of current at a low voltage.
Looking at one example online, a 40 x 40mm Peltier produces about 60 watts of cooling and draws around 6 amps @ 12 volts, and costs $14 (on Amazon, prolly not the lowest price out there).
You will want at least 6 or 8 of these things on there.
>Also, do you think that the Peltiers are really the best solution? It will be something around 0,125m3 to 0,512m3 (the inside, I mean), and will be put in temperatures from 21°C to 43°C at a maximum (for some thermophile bacteria, who knows).
Peltiers are used for mobile (car) coolers. These coolers don't get cold enough to make ice, but they will keep food in them cool. You could look up comments on those to get a better idea of how much they can cool--and Peltiers have no problems getting hot, they get hot a lot better than they get cold.
If you don't use Peltiers then the only other practical way to create cooling is a phase-change refrigerant system--like what a real mini-fridge uses. And forget about building that yourself, it ain't worth trying.
>>987754
>Looking at one example online, a 40 x 40mm Peltier produces about 60 watts of cooling and draws around 6 amps @ 12 volts, and costs $14 (on Amazon, prolly not the lowest price out there).
Okay, oops------that example above was for FIVE Peltiers, not just one...
I designed something like this.
It used a DPDT relay as a H-bridge to flip the current direction in a peltier module (when it's reversed, the hot and cold sides are flipped), an arduino, a LM35 temperature sensor and a seven segment display for the temperature.
Turns out I used an underpowered PSU, then an ATX one that died on the first night, and the relay I was using was rated for only 1 amp so it didn't really work, but you get the idea. I'll post a picture of the board I had made to control the peltier module and the fans (one to circulate the air inside the chamber, one to cool the heatsink on the peltier module).
>>987754
>>987758
Ok, you are scaring me now. That would be a ridiculous amount of power. I'm going to search about the optimum tension/current for these shits to work. And I tought about that too, but no fucking way I'm going to try a refrigerant system.
>>987763
I didn't understoon almost anything. Just clarify this to me: If I invert the current, the cold gets hot and the hot gets cold? Because if yes, I would need only one system, and would be less expensive to do.
>>987769
>If I invert the current, the cold gets hot and the hot gets cold?
Yes, that's how it works. The wires are red and black just so you know which way the peltier module is facing, but you can power it either way.
>>987769
>Ok, you are scaring me now. That would be a ridiculous amount of power.
It's not a lot of *power* because most Peltiers are only 12 volts,,, but it is a lot of current.
You can get 12v 30A CNC-style power supplies from China-land for only around $25 to $30 (some as cheap as $15 but I wouldn't trust the cheapest ones that much). And they are still only 350 watts.
>>987575
You only need one thermometer and a microcontroller/arduino/raspberry pi. If it's too hot, let the peltiers cool. If it's too cold, run the current in reverse and they will heat.
You will want the entire inside of the incubator to be metal, preferably copper, to spread the head from the peltiers as uniformly as possible through the chamber.
You also want to absorb the heat from the peltiers into a heatsink and then reject it. A CPU cooler works well for this.
You must also add lots of insulating material between the chamber and the outside world. The more the better. This is challenging around where the heatsinks of the peltiers are.
>>987809
Ok, so... does this have a name? I can't find schematics for something as you describe (I don't really know much about electronics, obviously). I'm still searching, anyway. Thank you for the idea. That may be the best way to do it.
>>987815
I meant electrical bill. Sixty watts per Peltier, 8 peltiers. Circa 4.800w non stop (the incubator is never turned off) (unless it only turns on as the temperatures go out of range, but that way I couldn't think of a proper time assumption).
>>987831
To be able to drive currents through a thing in two ways, you need an H-bridge. Usually employed with motors, but also works with peltiers.
60*8=480W, that's not superbad. Also, the actual power draw will be determined by how much insulation you have around the incubator's chamber. You can also get the power requirement from the conductivity of the insulation, but I don't think you know how to do that.
>>987831
>I meant electrical bill. Sixty watts per Peltier, 8 peltiers. Circa 4.800w non stop (the incubator is never turned off)
It won't run constantly.
How I would do this: arduino with 2 temperature sensors (internal and external) and one or more motor controllers, hooked to peltiers
1. You have a control time set up, say 1 minute and a heater/cooler run time of the same time or less--perhaps 45 seconds.
2. Every 1 minute, the arduino checks the external temperature first.
---2a. if the outside temp is above what you want inside, then the arduino checks the internal temperature sensor to see if the "cooler" needs to be run.
---2b. if the outside temp is below what you want inside, then the arduino checks the internal temperature sensor to see if the "heater" needs to be run.
The reason that you should check the outside temperature FIRST is so that the arduino doesn't constantly overshoot and undershoot the inside target temperature, always cycling the heat and cooling over and over again.
Only testing the inside temperature will cause this to happen, since the inside temp will change quickly. The outside temp will be far more stable, and the outside temperature will tell you if you should hbe heating or cooling the inside temperature.
I would use an 8-position DIP to set the temperature. It is cheap and relatively easy to change without reprogramming the arduino.
......
This (the "overshooting" issue above) is also the reason that I would rather do this myself programming a arduino--so I know exactly what the controller is basing its decision on.
>>987831
It'd probably cost about the same as running a crappy peltier fridge? Assuing op doesn't totally fuck the insulation.
>>987575
isis pls go
and stay go
