This is my first post, so greeting to everyone!

I have been poking around this forum, especially this Technical Repair section after I found some discussions about repairing HYS80-12J wine cooler controller board. However, I decided to start this thread with the objective to get information and advice, instead of repairing my wine cooler. I will maybe break it if I fail modifying it.
A bit of my background about electronic circuits, it is one of my hobbies. I built an AM radio receiver when I was 10 and I have had experiences repairing electronic equipment. So (I think) I am good at soldering and troubleshooting. But it is not my profession.

I have been searching for an air-tight cabinet with tinted glass door for a while. I plan to use it as an incubator to make Tempe (https://en.wikipedia.org/wiki/Tempeh).

Last weekend I bought a small, used and said to be a broken wine cooler for 40 €. After I brought it into my apartment, cleaned it up and as I was ready to disassemble it, I wondered why the seller said it is broken. So I turned it on and the fans were really noisy. I played around with the settings, set the temperature to 15 °C and a few minutes later the fans started to sound normally. And I put a thermometer inside it and within about an hour the temperature reached 15 °C. So it is properly working.

What I plan to do is to put a tiny heater and humidifier inside it. For making Tempe, I need to have temperature at 34 °C and relative humidity at 70%. I will regulate that with ESP32 micro controller. I will also use that ESP32 to turn on the cooler when the inside temperature goes above 34 °C.

It is a Klarstein MKS-2 (I believe) which part number is 10003453. It uses the controller board made by Foshan Hanyi which PCB model number is HYS80-12J. The maximum temperature that I can set is 18 °C. As I want it to cool down when the inside temperature is higher than 34 °C, I am afraid that it will unnecessarily run in full power due to 16 °C temperature differences. So I think either I need to add resistor in series with the NTC or change the NTC entirely for the temperature range that I am after.

Does anybody know the type of NTC thermistor that the board is using?

And do I need to entirely open the cover to expose the NTC?

Is there anything else which I need to consider in your opinion?

Thanks a lot in advance for your help.

 

Welcome to AAC.

Do you anticipate the internal temperature could reach >34°C if left unpowered in the environment where it will be kept?
What will the ambient temperature maximum and minimum be?

I suspect you we be far better off ignoring the cooling apparatus and creating a system to ventilate the cabinet (using positive pressure) with ambient air to cool it as necessary. Since the ambient air will (I am assuming) always be considerable cooler than 34°C, you can cool the cabinet with only a fan.

If you need to avoid air infiltration when not actively cooling, you can use an automotive HVAC blend door and blend door actuator to open and close the ambient air inlet as required. It may not be necessary to include active air movement, but if so, use a centriugal blower, not a fan. Fans cannot produce a positive pressure but blowers are designed to do it.

You should also implement a PID control system if you need to have a narrow temperature range maintained. This is a problem when there are compressors involved because they are very unhappy with short cycling. This means you will need to have a relatively large hysteresis on the thermostat to prevent damaging the compressor and so not have a narrow control range.

If you simply can’t allow ambient air into the cabinet* using one or more Peltier Effect devices is an option. the Peltier(s) would have to be mounted so one face was inside the cabinet and the other out. Sufficient heatsinking on the outside face is essential to the operation of the device, which cn include moving air over a heatsink.
*which would make the choice of a full face vertical opening cabinet seem problematic, so I assume this isn’t the case.

If empirical testing warrants it, a hybrid system of active (Peltier) and passive (ambient air injection) might be worth considering. In this case you would use an additional temperature (and humidity?) sensor to track the state of the ambient air and make decisions which cooling scheme to use based on the current internal and external conditions.

You could even do “two stage” cooling where you dump some amount of ambient air into the cabinet to rapidly cool, then switch to the solid state cooling to finish reaching the target temperature. This is all based on the idea that using ambient air alone is not feasible—but I suspect it will work perfectly.

In any case, you may be getting the idea I think you should be avoiding using the compressor—and you’d be right. It feels like using a 1kg machinist’s hammer to drive a carpet tack.

You will find researching some of these ideas helpful in your design. Do not assume your first impulse is the solution and turn your first ideas into a substitute for the actual problem to be solved. You are trying to solve the problem of maintaining the proper environment conditions for your Tempeh, not using the existing compressor to cool the cabinet—the latter may be completely unrelated to your actual problem.

Good luck with your project, I am confident you will come up with a working solution—just keep your eyes on the ultimate goal.

 

Thanks a lot Ya’akov for your comprehensive respond and advice.

Do you anticipate the internal temperature could reach >34°C if left unpowered in the environment where it will be kept?
What will the ambient temperature maximum and minimum be?

I suspect you we be far better off ignoring the cooling apparatus and creating a system to ventilate the cabinet (using positive pressure) with ambient air to cool it as necessary. Since the ambient air will (I am assuming) always be considerable cooler than 34°C, you can cool the cabinet with only a fan.

The temperature inside my apartment is normally around 22°C during winter and it can be up to 30°C in hot summer. So if I left my (will be) incubator unpowered, its internal temperature will not be able to reach 34°C.

What you have suggested was actually my initial plan before I knew that the wine cooler is actually properly functioning. But you are right, it does not make sense anymore to keep the cooling system anymore. I will go back to my initial plan.

If you need to avoid air infiltration when not actively cooling, you can use an automotive HVAC blend door and blend door actuator to open and close the ambient air inlet as required. It may not be necessary to include active air movement, but if so, use a centriugal blower, not a fan. Fans cannot produce a positive pressure but blowers are designed to do it.

Thanks for your suggestion about HVAC blend door, blend door actuator and centrifugal blower. I will consider that. I hope I can find smaller ones which can be fitted into the back side of the cabinet.

If empirical testing warrants it, a hybrid system of active (Peltier) and passive (ambient air injection) might be worth considering. In this case you would use an additional temperature (and humidity?) sensor to track the state of the ambient air and make decisions which cooling scheme to use based on the current internal and external conditions.

I am actually planning to use the hybrid system as you suggested. And I plan to install 5 sensors which ESP32 micro-controller can still managed. Those will be for measuring the inside temperature, outside temperature, temperature of the heater (I am not sure why I thought this is necessary), humidity and CO2 level inside the box. So that I can improve my design base on the historical statistic of the data from those sensors.

About my progress, I am still trying to find the best way to have a good air circulation inside the box. I have just disassembled the peltier and the radiator this morning (I have been busy with my work this week). I would like to explore my options in installing the fans or a centrifugal blower. But I am having difficulties to open its back cover. It seems to be glued to the inside wall. The back of the box now looks like on below picture.



Does anybody know how to safely remove that back cover without ruining it as it is made of a thin metal? Should I apply heat with heat gun?

It looks like on below picture before. I hope I didn't miss a step in dismantling everything that was screwed at the back, so that it is now difficult to remove the back cover.

 

It would help if you could label the photos so it would be more clear what you are referring to.

If you are talking about the plate with the two bolts (black on the outside side, silver inside) it appears it could be spot welded to the back panel or through it so that there is a flange. If that’s the case you‘ll need to drill out the welds to remove it.

The easiest way is probably with an appropriately sized step bit.

 

I am sorry that I was not clear enough on what I was referring to.

I would like to open the whole metal plate at the back side which is indicated by the big red rectangular on below picture. I have already removed all screws but I still cannot open that. It seems to be glued to the inside wall.

If you are talking about the plate with the two bolts (black on the outside side, silver inside) it appears it could be spot welded to the back panel or through it so that there is a flange. If that’s the case you‘ll need to drill out the welds to remove it.

It is easy to open the plate with two bolts (the small red rectangular on the picture above), by removing the screws on the heat sink on the inside box. That is actually the hole where the peltier (at the back) and the heat sink (on the inside) are located. As you can see on the above picture, where I focused my camera to the bottom of the radiator heater in my apartment.

A part from exploring my options in installing the fans to have good air circulation inside the box, I would also like to be able to access the circuit board of the control panel. I suspect it is located at the back side which connector to the control panel is at the top of the door hinge as shown on below picture.

 

I have finally managed to open the back metal cover. I started with scoring the side and bottom parts with a small putty knife. Then I carefully pushed a metal ruler from the bottom, and pushed a metal cabinet handle on top of the ruler to crack it open. I did it slowly little by little from the bottom to the top of the cabinet. Below is the result with primitive tools on top of the back metal cover on the left.