Replacement refrigerator controller

[Michael] got his hands on a refrigerator that he intended to store beer in but found that it ran constantly. Instead of buying a new thermostat he and his friend [Doug] set out to build an Arduino-based controller for the fridge.

The finished project will switch 240v so they’ve used a transformer to power the logic circuitry and a solid state relay to handle the load switching, with a Dallas 1820 for temperature data. Because the Arduino offers more capabilities than the average thermostat hack they also decided to tap into its potential by adding an Ethernet shield. We see the Arduino as a prototyping device and so do these folks. Once the bugs in their first PCB prototype are worked out the circuit will use the ATmega328 and do away with the Arduino.

[via @littlebirdceo]

Comments

  1. Spork says:

    Wow. I don’t know what to say. Properly implemented arduino, safety when dealing with real electricity. (note the acrylic and proper separation of traces for power)
    I can only assume this is a christmas gift from you hackaday, so thanks!

  2. spinster says:

    Total solution cost around 40 dlls? thermostat 5 dlls. And YAAP? (Yet Another Arduino Project) I’ll pass

  3. Mr. Q says:

    no twitter feed with beer temperature?

  4. jh says:

    @spinster
    try googling refrigerator thermostat. there are a few (and I mean very limited few) that are less than $10. Most are around $50 or so.

  5. john personna says:

    Cool. Two groups have been hacking chest freezers to be refrigerators: beer makers and enviros. Apparently the shape and insulation on chest freezers make them extremely efficient as fridges.

  6. aonomus says:

    I see no mention of optoisolation anywhere. At the very least they should consider it, since 240VAC into the USB port can ruin anyones day.

  7. Paul Potter says:

    Superb. I would love to do something like this. Beer and tech together. Win.

  8. Rex says:

    @aonomus
    He is using a solid state relay. They have built-in isolation. You can find them on ebay for about $10 and they can control 40 amps. An Arduino port can turn them on and off.

  9. Murray says:

    Once you have a micro controller on board, you have to add one feature. It costs nothing to add and can save you a lot of money… If the compressor is running, and the power fails briefly, when the power comes on again, the compressor switches on, but because of the back pressure, some times, the motors stalls, overheats, and burns out. It is recommended, that once the power comes on, the system waits 10 – 15 minutes before starting, for the pressure to bleed off, before operating normally.

  10. trollingmotor says:

    What an amazing coincidence!

    I just replaced the controls and sensors on my mid-range pricing electrolux/frigidaire side-by-side… it is a long story. I make candy as a hobby, and I have other friends who also enjoy my hobby. Also, I am “common law married” to a very skilled pastry chef here in Massachusetts, so the refrigerator is of central impotence in my life.

    I want to point out that frigidaire/electrolux products are in fact designed by people who care too much, and that many of them went on to design the Vista operating system,which was later marketed as Windows 7.

    But let us return to Frigidaire/Electroluxe.

    It turns out that these firms had a long run of bad designs between 1996 and 2010. Many of these involved “economic engineering” – you know, of the “let’s ditch the crusty old farts and replace them with some young guys who understand the internet and social networking” variety”.

    The new breed was very focused on the future.
    However, this didn’t work out so well for the consumer, as ICQ turned into AIM, and AIM turned into facebook, and facebook turned into a popular place to avoid doing actual work.

    By 1998, the average life span of certain brands of appliances started dropping, and by 2003 had dropped from ~2.7x down to about 1.3x, where x was the warranty period.

    Of course, since that Edward Deming guy died, 1.3x isn’t what it used to be, so let’s pretend that it’s now a random number providing us with a working appliance for something between 30 days and -rarely- as much as 9 years.

    We made it to 7 years before my refrigerator started making Darth Vader “breathing” sounds a few months ago. A few hours of googling revealed that almost any appliance attached to the firm of electrolux/frigidaire (they have about 30 names) seems to have dreadfully short lifespans… and in every case, repair was “non-economic”.

    Being the chipper supporter of the american way that I am (I plan to vote Palin 2012 and hopefully she’ll replace the constitution with a modern EULA modeled after the very successful one used by Microsoft), I decided to fix the system the right way… by ripping out the control board.

    The control board wasn’t broken, by the way – it’s just that bad software costs less than good software. The holidays were coming, and we had a lot of candy to make and pack for the gift shops.

    Also, I am unemployed, so I must run our business by default. However, I had most of November to work on this a little at a time.

    Refrigerators are not sophisticated. It wasn’t hard to locate the sensors – and replace them with solid state temp sensors, including drilling and epoxying new sensors spaced at 10 inches up the side of the fridge, as well as at various points in the freezer and fan compartments.

    Let me be the first to say that I went overboard, using almost 24 temp sensors, 4 current sensors and two thermocouples. I won’t say what board I used, but my craptacular software lets me either write or read a string to the system from a PC.

    Writing simply turns things on and off (compressor motor, vent controls, heater, etc). I left the fridge light and water/ice dispenser alone, apart from reading the temps and motor status.

    I basically read a long string of ASCII hex that corresponds to each sensor with resolution equal to about 10 bits. Accuracy isn’t much to write home about, either.

    Before I pulled the board, I recorded the values for 3 days. I made some mistakes in writing the software, but the fridge was basically empty (we have 3 of them, thanks to late 20th century economic models) at the time. Also, the electrolux/frigidaire had been spoiling milk for some months, so we were ready for the worst.

    Did you know that milk often sits unrefrigerated on docks for hours at a time before it gets to your display case? You do now. It’s also common practice to turn off the refer portion of trucks for several hours and overnight to save fuel.

    In fact, I had assumed that this was the cause of our milk going bad so frequently until I discovered that my fridge was randomly popping up to 54F for a few hours every three days.

    BTW, my problem was ice buildup on sensors due to issues with the ice maker. The electolux/software didn’t take this into account, and was telling the fridge to both blow and not blow at the same time. Life on mars, as it were.

    My housemate/life partner (let’s call him Klaus) is not happy at the fact that I have done this, as it took a great deal of time. Also, the fact that I re-purposed our Kitchen’s electronic picture frame to provide status information has annoyed him to no end, and as a result I did not find any fudge in my sock, only peanut brittle and a Sarah Palin calendar.

    In the end, it was not cost effective, and we will likely buy a new unit. However, I am very happy at the results. I will say this:

    1) Use relays for low duty cycle AC control, and solid state relays or zero-sensing Triacs for variably duty cycles.

    2) It is as easy to wire 8 sensors as 1, if you use a multiplexor or use I2C sensors. Calibration is another story, because I needed to measure below 0C, so one must use dry-ice. Better to use pre-calibrated sensors. Calibration was the worst part of the project.

    3) low cycle times with some temperature drift is better than continuous control. The compressors do not like to be manhandled, so you should try to control the fridge side with the fan and vanes.

    4) I worried about drilling the insulation, who knows what this is made of?

    5) Read a few articles on refrigeration before you do this. You can easily replace a thermostat, but if you want to be more sophisticated, you should understand the cycle.

    6) MS C sharp is the new visual basic. It’s like C flavored VB.

    My next project will hopefully be an automated fudge packing machine. It will be powered by an arduino, since I am curious about such things and often see them mentioned here.

    The problem is that Klaus and I have so little time together – It is my desire that we can make each batch, and then put the slab into a machine that will cut the pieces and arrange them.

    I hope to also have each piece wrapped in tissue, but my mechanical abilities are not so good.

  11. St.Jimmy says:

    You mean…

    No, it can’t be.

    A properly implemented Arduino project!

    YAY!

  12. tj says:

    Yo dawg I hear you like arduinos..

  13. trollingmotor says:

    I am serious about using an arduino for my next project, and am not trying to be funny. If I use an arduino, I don’t need to solder.

    Also, I apparently burned the floor on accident while soldering, so that didn’t go well, also Klaus is worried about lead fumes.

    I was happy to do the project, as it was conceptually very simple and rewarding… each step turned out just as I imagined, except for a simple software mistake caused by using simple variable names.

    I confused i and j, when I should have used names like RightHandCompartmentVentilatorReturnDuctTemp and RightHandCompartmentProduceCrisperTemp to avoid such confusion. C sharp is not my first language, though, so I am not used to Hungarian notation other than what I have read. Once again, Microsoft leads the way!

    Because of this, the system was trying to keep the fridge at too warm of a temperature, but it was a simple mistake. I am not expert, I just know sensors and some programming.

    The picture frame as a monitor was a stupid idea, it would have been easier to just put an LCD on top of the fridge, but as I worked on the project I realized that Klaus didn’t like the wires hanging everywhere.

    I stole the frame idea from another project here on hackaday some time ago, I used it to put up funny pictures when my parents came to visit us.

    I know some electronics things from my father, who built instrumentation, as did his father before he moved to Georgia. My grandfather lived in the place where I met Klaus, Peenemunde in Germany.

    Also, my grandfather moved back there in 1978 and started another family so we all visit them. It is beautiful, and very interesting if you like museums… and candy! The best candy shops in the world. Swiss chocolate is over rated!

  14. @Spork, didn’t even notice the acrylic until I read your comment. I agree great touch.

  15. tehgringe says:

    lol@trollingmotor

  16. Adam says:

    @trollingmotor, Loved the comments. You should avoid Hungarian prefixes, Check out Microsoft’s naming guidelines: http://msdn.microsoft.com/en-us/library/ab6a8y1b%28VS.71%29.aspx

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