The final build of the Climate Chamber that fits around the microscope.

CREATING AN OPTIMAL TEAR CRYSTALLISATION ENVIRONMENT

THE PROCESS & CREATION OF THE DIY MICROSCOPE CLIMATE CHAMBER & CLIMATE CONTROL UNIT.

In order to get better and more consistent results for the project Imaginarium of tears, it’s important to standardise the evaporation and crystallisation process of tear fluids. To do this, I would need to create a climate chamber around the microscope, and a climate control unit to control the temperature and humidity within that climate chamber at preset values.

With the experiments done for the Tear Collection Kit, data tells me that the optimal temperature and humidity of such a climate chamber would be around 12° Celsius and 40% humidity.

Example of the tear evaporation and crystallisation process.

To do this I would need to upgrade the microscope by building my own DIY climate chamber and a climate control unit.

Current Microscope Setup with the DIY scanning stage.

Knowing that the microscope had an optional incubator mentioned in its original manual, I went on the internet to see if I could buy the old incubator. Unfortunately as I expected, finding only the casing and or the control box was not easy. Setups where only sold together with the microscope, making it too expensive to justify. Other options like a 3rd party manufacturer where not supporting this microscope or where also just to dam expensive.

The original optional Incubator mentioned in the original manual as available accessory.

1.) The Climate Chamber:

With the information available form the manual and images from the internet, I decided to design the Climate Chamber myself. Below you can see the preview of the climate chamber, designed by measuring the specific parts of the microscope insuring a snug fit. Tho I did make some adjustments when it came to the “original incubator” design.

Click link to open the fusion 360 file and review the Climate Chamber model: http://a360.co/2F5LfVD

Things that where adjusted :

  • Brackets to connect to the microscope.
  • Smaller casing, shorter on the left and right side.
  • Placement and type of manipulator doors, no hinges but sliding doors.
  • In and outtake exhaust to later connect the climate control unit.
  • Use of “connectors” in the corners. No glue needed, everything is build modulair with nuts and bolts. This is an important design change, due to traveling everything needs to be easily disassembled into a flatpack.

The idea is to 3D print all of the black parts using my Ultimaker 2+, 3D printer. All transparent parts will be made out of 5mm Plexiglas, and laser cut to achieve high accuracy and quality.

You would almost say “Why not build a big case around the microscope? “

2. ) Climate control unit:
The second part I’m now working on is designing the “climate control unit”. A far more expensive and complicated design then the climate chamber itself. Essentially the climate control unit needs to be able to cool, heat, humidify and dehumidify. This to provide the set temperature and humidity within the climate chamber that is placed around the microscope.

Latest design of the Climate Control Unit that will be controlling the temperature and humidity within the Climate Chamber.

Most important for this design, reaching the ideal tear crystallisation temperature and humidity. But to enlarge the potential in the future, the system will be build to reach a larger range of different temperature and humidity rates. If everything plans out, it’s potential temperature range will be between -5 to 50° Celsius, with the according possible relative-humidity rates.

To do this the design will be built out of 4 units, these will later be combined into one design. The units that are going to be built are;

Cooling unit:
For this cooling unit two Peltier elements of 12V, 15A (217W) will be used.
On the hot sides (outside) of each Peltier element, there will be a CPU heat-sink with 4 heat pipes and one 120mm fan. On the cold side (inside) there will be a heat-sink of 170mm x 70mm x 40mm with 35 fins. This setup will be able to hit temperatures of up to -50° Celsius on the cold side of the Peltier. Air passing the inner heat-sinks will then be cooled and moisture from the air will be removed. To get rid of all condensed or melted ice water, a “water collector” with a drainage hole is placed on the bottom.

* By reversing the polarity on the Peltier elements, they can also be used to support the heater when needed. Since changing the Peltiers polarity will result in reversing the hot and cold side.

* When we use the heating unit we can also turn on the cooling unit to faster dehumidify the air.

“Cross section” of the cooling unit; showing all the parts, eventually all transparent parts will be made of aluminum.

In the future a extra unit will be built to “locally” boost the process of lowering temperatures. This will be done by adding a 20x20mm Peltier to the microscopic slide holder. The cold side of the Peltier element will cool the aluminum microscope slide holder. Cooling the microscopic slide in time.

To dissipate the heat from the hot side of the Peltier a water cooling block will be used. The heated water will then be cooled between in the cooling unit of the climate control unit. This will take some adjustments on the unit, and a water pump to move the heat.

A NTC probe will be used to measure the temperature directly on the microscopic slide, by doing this we can control the temperature of the extra cooling unit.

Future update to boost the cooling process, a Peltier of 20x20mm with a water cooling block on a microscopic slide holder.

Dehumidify unit:
For the dehumidify unit the same setup is used as the cooling unit, the only difference will be the addition of a few small 40x40mm fans to increase the warm air flow around the freezing heat-sinks on the inside. This hopefully will prevent that the condensed water will freeze on the-heat sinks, besides that it should help to speed up the dehumidification of the air.

* This unit can also be used as a secondary cooling unit, to speed up the process of lowering temperatures. If this is the case, the 40x40mm fans will be turned off.

“Cross section” of the Dehumidify unit; showing all the parts, eventually all transparent parts will be made of aluminum.

Heating unit:
If you are familiar with a Peltier element you would say why create a separate heating unit… Well for this design separated, modular and multi purpose units where important to me. This would give me more flexibility, in this case I can run the heater and use the cooling and dehumidifying unit to both lower the humidity when needed.

For the heating of air 2 PTC units of 150W, 12V are going to be used, which hopefully are enough to heat up the chamber to 50° Celsius. If not, and humidity is at the right temperature, one or more Peltiers can be turned into heating units and support the heating of the PTC units.

“Cross section” of the heating unit; showing all the parts, eventually all transparent parts will be made of aluminum.

But we don’t want heat the air to high, this since the equipment is not made to handle high environmental temperatures. Next to that it would be very inefficient to heat the whole chamber to 100° Celsius. To be able to reach high temperatures in our sample a local heating solution will be used.

Above you can see the microscope cover slip holder that is made out of aluminum, attached to it are two Aluminum Housed Resistors + NTC probe.

By using this setup with two Aluminum Housed Resistors of 10 to 25W we can influence the temperature directly of the microscopic slide holder. By heating up this microscope slide holder we also heat up the slide itself. By using a NTC probe we can measure its temperature directly and influence the Wattage needed to reach our temperature goals.

Humidify unit:
By using a ultrasonic water atomizer, we are able to create small water vapor. This vapor will be introduced into the airflow with a small 40x40mm fan. By doing this the humidity in the Climate chamber can be increased with a maximum of 400ml an hour.

The Water basin will be filled with demineralised water to prevent any impurities in the water to “clog up” the unit. To get to the basin, we have to take of the hood and the “air”cone and we can fill it up when needed.

“Cross section” of the humidify unit; showing all the parts, eventually all transparent parts will be made of aluminum.

If we only combine the units together without all other needed parts we would get something like this.

All 4 units placed together, without in-take hood, out- take unit and control box.

But the “Climate Control Unit” also needs to have proper intake and out take of air from the Climate Chamber to be able to change the temperature and humidity.

Airflow:
The air will taken from the Climate Chamber trough a ⌀82mm air hose. Once it reaches the Climate Control unit, the air flow will be guided over a “cone” and send to the correct unit. Creating the correct airflow will be done by using 4 air dampers that are controlled by small servo’s. Depending on the temperature and humidity that needs to be achieved the corresponding air dampers will be opened to engage the airflow to that unit.

This image shows the top hood of the Climate Control Unit, above you can see the ⌀82mm air intake, together with 4 servo’s to control the air dampers. In this case the top hood will be made out of Plexiglas in stead of aluminium.

To create airflow an 12V, 4A, 120mm fan will be used in the bottom of the climate control unit, this will generate suction and start the airflow.

This image shows the bottom exhaust part together with the 120mm power fan and the outtake connector.

As you can maybe tell, most of the units are modular and multi purpose except for the humidify unit. This hopefully enables me to create a wide spectrum of available temperatures and humidity combinations.

Electronics compartment:
Power supply: To power this Climate Control Unit, a Server grade HP power supply will be used that will supply the unit with 12V (1200W and 100A). Since most of the used equipment is 12V we can directly use the 12 different outputs, (100W, 8.3A) and when needed we can combine different rails to achieve higher wattage and Amperage.

Buck Boost Converters: To generate 5V and 24V buck boost converters are used. 24V, 1A for the ultrasone water atomizer, and 5V, 2A for some other small components.

Solid State Relais: To switch on or off different components in our units we will use relais.

Brushed ESC: Since we want to regulate the Peltier element pairs per unit, a brushed Electronic Speed Controller will be used to limit the amount of electric draw.

PWM Servo Motor Driver I2C Module: To control the 4 servo’s that are connected to the air dampers we will use a PWM server motor driver controller.

Micro Controller: To be able to control everything a Arduino ATMega2560 is going to be used, this will become the brain which everything will be connected to.

The electronic compartment box made out of aluminium, with a 9mm plywood board that can be taken out to inspect / change the electronics.

The USB port can later be used to control the unit over the serial bus by using processing to communicate and read out all values. Everything will be controlled and logged by software so no external buttons or displays are needed.

The banana plugs will be used to attach the different sensors and external modules. “Two channels” might be a bit scarce so probably there will be more in the final build.

Channel 1, 4 connections:
Adafruit AM2315 — Encased I2C Temperature/Humidity. This will be used to measure and control the temperature and humidity inside of the climate chamber.
Channel 2, 2 connections: 
External NTC temperature probe on the microscope cover slip holder. This will control ether the external aluminium housed resistors, or the external Peltier element.
Channel 3, 2 connections:
 External heating unit on the microscope cover slip holder, that powers the Aluminum Housed Resistors
Channel 4, 2 connections
External cooling unit on the microscope cover slip holder, that powers the 20x20mm, 12V — 5A Peltier.
Chanel 5, 2 connections 
Power cables to the external power pump.

Depending on the heat generated in the Electronics compartment small 40x40mm fans will be added to generate a proper air flow. (not yet included into the design)

To give you an idea on how this would look when all is put together another image can be found below.

Latest design of the Climate Control Unit that will be controlling the temperature and humidity within the Climate Chamber. Rendered transparent to show the inner workings.


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