back to article Internet of Things fridges? Pfft. So how does my milk carton know when it's empty?

In today's incredible Internet of Stuff Things world, the fridge is going to tell us we need to restock it with more milk and butter. What bunch of nutters thought this idea up? Let's take a patient walk through what a fridge would have to do to accomplish this, and then ask why it would be better than a fridge user's scan …


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  1. Neil Barnes Silver badge

    The internet of fridges

    What is actually 'required' - I use the term loosely, as in perhaps something that might be marginally useful - is a current picture of the inside of the fridge, so I can bloody well see what's in there (or not in there) when I get to the cheese counter.

    Of course, there are still technical challenges to overcome - for example, if the door is shut, the little light is out, so the picture will be rather gloomy. Infrared isn't going to work too well, what with the cold in there... but I'm sure there's nothing insurmountable a couple of doctoral candidates couldn't sort out.

  2. cambsukguy

    Re: The internet of fridges

    I think this is close:


    If it takes a picture when you open the door, or, better still, just as you close it, the end result would be a close approximation to the current state.

    You brain will still have to remember whether that milk carton was light or heavy and how old the milk was of course.

    If only they changed the bar code to put the week or day number of the use-by date on the end, or printed them separately on all sides of the carton(s). Then a camera/software could, at least, tell you what was coming to it's useful end - I could then add a couple of weeks manually.

  3. Elmer Phud Silver badge

    Re: The internet of fridges

    "if the door is shut, the little light is out,"

    But is it?

    Is there a cat in the fridge as well?

  4. TRT Silver badge

    Re: The internet of fridges

    *switches from IR scanner to UV*

  5. Anonymous Custard Silver badge

    Re: The internet of fridges

    Hang on, Heath Robinson and Rube Goldberg were supposed to be satirists, not visionaries.

    Somewhere in heaven they'll be having a good laugh at all this nonsense methinks...

  6. John 156

    Re: The internet of fridges

    ""if the door is shut, the little light is out,"

    But is it?"

    Yes it is, by inference, as you will find a lever at the top of the fridge which can be operated manually instead of by the door to switch off the light.

  7. Bullseyed

    Re: The internet of fridges

    No, optical isn't necessary. RFID does the task.

    "Terrific. How does it know it needs topping up? No, really. How does the fridge know it's running out of milk, butter and cheese? These things are just cartons or plastic bags with stuff inside them. How does a freakin' fridge know what's inside them? Is it supposed to have some form of food item pattern recognition capability that can also detect actual amounts of solid or fluid foodstuffs?"

    We're not far away from RFID price tags and expiration dates. We can use temperature sensitive "stripes" as part of this, which then can determine things like the full-ness of a gallon of milk or a box of butter. Some other items obviously get harder, like a head of lettuce, but other items are easy like cups of yogurt.

    The other option is weight based shelves. The fridge knows what is on the shelf so it knows what the weight should be. It counts out things it knows like the aforementioned yogurt and milk. It knows how much a box of butter should weigh and a head of lettuce, so it can "guess" the level of butter/lettuce within a reasonable rate, combining some optical sensors for things like size of the head of lettuce.

  8. Keith 21

    Re: The internet of fridges

    """if the door is shut, the little light is out,"

    But is it?"

    Yes it is, by inference, as you will find a lever at the top of the fridge which can be operated manually instead of by the door to switch off the light."

    Yes, but when the door is closed, how do you KNOW that lever has actually switched the light off?

    All you know is that with the door open, move the lever and the light goes out. When the door is open.

    When the door is CLOSED, however, you are in a different scenario, with no way to observe, and all bets are off.

    Oh, and don't for one second suggest one could add a camera to observe the inside of the fridge, for then one has changed the conditions again and entered a third scenario...

  9. Matt Bryant Silver badge

    Re: Bullseyed Re: The internet of fridges

    ".....RFID does the task..." Half the task anyway. The other half is by having designated holders in the fridge into which you put a standard measure each time. At the bottom of the holder is a simple electric scale that measures the weight remaining - it already knows the full and nearly-empty weights for set measures (like a litre of milk or a 450g bar of butter) and you can program new values in for new standards you want to set, and adjust the nearly-empty values up or down dependent on your consumption pattern. RFID tags will cover you for the items you use all of at once and will automatically update inventory when you put your shopping away. You could even design one that used barcodes now and not even bother with RFID. Sound too complex? Not really. I once worked on the design of a system for an automated factory that held a stock of over 2000 different components in smart bins, each bin having a similar scale built in, and when the weight of the bin fell to a particular level (equivalent to three working day's worth of that component by weight) the system automatically ordered more. The back end was a single-CPU UNIX server that ran a simple database (PostgreSQL IIRC). That was about fifteen years ago, so you could probably run the same code on a Raspberry Pi today.

  10. ItsNotMe

    Re: The internet of fridges

    There isn't a snowball's chance in Hell I would ever connect anything in my home, other than a computer, to the Internet.

  11. John Deeb

    Re: The internet of fridges

    Bulleyes and some follow-up comments. The weight based shelves would only work if every item in the fridge is RFID enabled and not thrown at the shelves and containers in a chaotic way but preferable in a neat sequence. Just like programmers would fill their virtual fridge in a fricking demo! In real messy life the fridge will forever remain in a partially confused state.

    "Sensitivity stripes" would be a problem on items where the packaging is already too much part of the cost and recycling woes. And as you already wrote, fridges of people not working on these projects - with less predictable and organized live - are often filled with many fresh, self-made, rather undefined and other unpackaged items. So then we need to have two administrations where there was only one before.

    But with large scale applications, like storage rooms for massive food preparations, high volumes, predictable items, this could be actually useful. And as someone else already wrote here, it's already being done. But at consumer level it's in the "hoover car" and "jet pack" category for sure!

  12. Richard 12 Silver badge

    Re: The internet of fridges

    No RFID is completely and totally stupid for this.

    The only things you need for this are much, much cheaper and are already used in some food dispensers and also the pick'n'place machines that made the PCBs in the computing equipment you're using to read this.

    ♳ Every shelf has an array of weight sensors.

    ♴ The fridge has an array of relatively high resolution cameras watching the shelves from several angles.

    ♵ Tracked foodstuff item packaging has a 2D barcode printed on it.

    ♶ The fridge then uses the cameras and 2D barcodes to identify the foodstuff, use-by date and 'full' and 'empty' weights of each item.

    ♷ The array of weight sensors then allows the fridge to figure out whether a given container is nearly empty, and the historical database indicates when a given type of item has gone completely.

    In theory the existing 1D barcodes that are already on almost everything give nearly enough information - they identify rough product groups (not specific products as UPCs are expensive), which is probably good enough for most purposes as "500ml Muller yogurt" is usually enough, even if you don't know the flavour.

    They don't include the use-by dates though.

    (Excessively ornate bulletpoints included because the whole idea is excessively ornate)

  13. Mike Dimmick

    UPCs are incredibly cheap

    Membership of your national GS1 subsidiary costs a couple of hundred to a couples of thousand dollars depending on your company turnover. GS1 UK charge £107 joining fee and £117 annual membership if your turnover is under £500k, which entitled you to codes for 1,000 distinct products. There is no per-product fee. You just have to include the barcode in the label you were going to print anyway. It literally costs nothing beyond ensuring that the printed label is in spec.

    For turnover of £1bn or higher, the joining fee is £327 and annual fee is £2,602, which gets you a prefix valid for 100,000 product codes.

    A Global Trade Item Number (UPC is a subset) describes one product. Not a family. In the milk example, skimmed milk will have a different code from semi-skimmed. A 2pt container will have a different code from 1pt. Organic a different code from regular, from value. Order the same code and you'll get the same back.

    RFID tags contain the GTIN as one of the data components, so you don't make any saving compared to a paper barcode - you still have to be a member of GS1 if you want to sell your products at any retailer. If you just want to sell your products in-house, there's a range of GTIN codes reserved for private use.

    If you want fewer than 1,000 codes, you can go to a reseller who will register your product under one of their prefixes. They can be a lot more expensive per code. You still only pay once to register the product, every use of that code is free.

  14. Mage Silver badge

    Re: The internet of fridges

    Actually I don't even want my computer connected DIRECTLY to the Internet ever again ...

  15. Deltics

    Re: The internet of fridges

    You just extended the problem domain further....

    If the fridge works it's magic by knowing what items are on which shelves then it must also now be able to accomodate the situation where someone removes an item from one shelf and then carelessly replaces that item on a DIFFERENT shelf.

    "Honey, where did you put the yoghurt?"

    - "In the fridge"

    "Yes, sweetness of my life, but WHERE in the fridge?"

    - "Oh for pity's sake, I can't remember.... ask the damned fridge"

    And, better yet, when the said item has in fact been depleted, do we require now that the consumer replace the empty packaging back in the fridge so that the appliance can be apprised of the food item depletion incident and can thus inform the consumer (who of course already depleted it) ?

    Otherwise, how does the fridge tell the difference between "We've used up all the milk" and "Janet/Bob left the damned fridge out on the worktop again, the lazy cow/git" ?

    Or even "We've run out of peanut butter" and "Some idiot put the peanut butter in the pantry instead of the fridge".

    No, sorry. Weight based shelves or any other "solution" to any problem int he domain that you think you might have come up with simply create MORE PROBLEMS.

  16. big_D Silver badge

    Re: The internet of fridges

    It's a gnome, not a cay. They will be replaced by artistic gnomes in the future, who draw a quick picture of the fridge, before he takes a swig of milk and turns off the light.

    I always look at the fridge when I make the shopping list, before I drive to the supermarket...

  17. big_D Silver badge

    Re: The internet of fridges

    @bullseyed we work with RFID and a disposable tag on a carcass for traceability is 'too expensive' for the supply chain, because they can't be made for less than 10c.Even if the price of every item on the shelf in the supermarket went up by a couple of cents to cover the RFID chip, just for the 2 people who have bought a smart fridge, the public would revolt. For 99% of people, this is an irrelevant 'first world' problem that they don't need a solution to.

    If I buy a new device, it needs to save energy, not use more energy to give me useless information.

  18. graham_

    Re: The internet of fridges

    "when the said item has in fact been depleted, do we require now that the consumer replace the empty packaging back in the fridge"

    That's what everyone in my house does, maybe smart fridges should start on tackling these bigger issues

  19. Handler

    Re: The internet of fridges

    How do you account for leftovers or the residue from take-away dinners?

  20. hplasm Silver badge

    Re: The internet of fridges

    " will find a lever at the top of the fridge which can be operated manually instead of by the door to switch off the light."

    Only when the door is open...

  21. John H Woods Silver badge

    Devil's advocate says...

    ... containers don't need to be smart if it scans in and out and the shelves have weight sensors. If it knows that you have taken a 1pt carton out, it got 595g lighter, and when you put it back in it only gets 205g heavier again, then it knows you've used 390ml milk and that you have 178ml left.

    But I think it's more likely that your supermarket could tell you than that your fridge could: "Hey, John, you used to buy 2pts milk a day and one box of Cap'n Crunch a week but you haven't bought much milk recently, do you need more?"

    This approach is still fallible, of course: "No thank you, Tesco, now that my sons are teenagers I just have milk piped from the local dairy. And when we run out of cereal I have to call Eddie Stobarts"

  22. Anonymous Custard Silver badge

    Re: Devil's advocate says...

    Judging by the interior of our fridge after Herself has emptied our local Tescos, having weighing shelves wouldn't work. It tends to get so much stuff in there, often stacked up, that it looks like a chilled but edible variant of Tetris.

    Plus if you can only put stuff on allocated spaces inside the thing, then it'll also need standardisation of packaging shapes/materials (for uniform weight from brand to brand) which is a whole other ballgame.

    There is of course the slightly easier options of a "to buy" list stuck on the door of the thing that gets filled in as things are used up (or getting close to being used up) which then becomes part of the shopping list, or of course just looking in the damn thing and quickly inventorying it before going shopping.

    But of course neither of them are innovative, sexy or high-tech (unless you stick a tablet onto the door to act as the list), they just quietly work (most of the time)...

  23. TRT Silver badge

    Re: Devil's advocate says...

    I keep leftovers in my fridge...

  24. Anonymous Coward
    Anonymous Coward

    Re: Devil's advocate says...

    Unexpected item in refrigeration area!

  25. I ain't Spartacus Gold badge

    Re: Devil's advocate says...

    Unexpected item in refrigeration area!

    Soon followed by, "share and enjoy!"

    Then very rapidly followed by, "die bastard fridge die!!!" [sound of hammering]

  26. Danny 4

    Re: Devil's advocate says...

    @John H Woods

    That was my initial thought. But if you picked up two objects simultaneously - or rather put them back simultaneously on the same shelf... (It would know what was taken from the fridge and therefore already knows the previous weights.)

    The scanning sounds like a lot of faff. Though I'd be up for one if, across the door threshold, the scanner was the laser mist from Alien. It would also keep the nasties inside the fridge (or the other way around - keep them out?)

    Otherwise, I agree: a solution to a non-existent problem.

  27. TheOtherHobbes

    Re: Devil's advocate says...

    You don't need weight sensors or Magic Milk Measuring Things.

    You just need some shelf-life/usage stats and a timed reminder - which are easy enough to organise with an RFID reader.

    If you were really clever you could count the number of times the carton was in/out of the fridge, and use that as part of the usage estimate.

    You could even - here's a thing - include the use-by date in the RFID tag.

    It won't be perfect, but it will be cheap. And good enough for things like bread and milk.

  28. Isn't it obvious?

    Re: Devil's advocate says...

    I think we're far more likely to see ubiquitous RFID tags on everything that has a sell-by or use-by date. In 5-10 years (thinking the average expected lifespan of in-service fridges) I can easily imagine RFID tags being cheap enough to stick on anything from a carton of eggs to a container of yogurt. And if they're cheap enough for that, then they _will_ be on everything, because of the stock-keeping hassles it will reduce for wholesalers/retailers.

    So then it's just a matter of your fridge inventorying everything that goes in with an RFID tag. _That_ technology is already cheap enough. Obviously it won't be able to keep track of your fresh vegies, but it can track anything packaged. And assuming you don't put empty packages/containers back in, it can tell you (for instance) you're out of butter. (It won't tell you that there's only enough left for one slice of toast tomorrow morning - at least not at first.)

    And who knows, maybe someone bright can figure out a way to use resonance or path timing or who knows what other emergent phenomenon to get a liquid level off a container with an externally-applied RFID tag at a known position. There's loads of people way smarter than I am; I'd be daft to say it can't be done.

  29. Lost in Cyberspace

    Re: Devil's advocate says...

    I can see Tesco, ASDA, Sainsburys et al enforcing it so suppliers won't have a choice.

    My library changed from barcodes to RFID sometime in the last decade (since I last took out a book), so I'm sure groceries will go that way at some point.

    Now, forget about fridges for a sec - if every door in my house had RFID sensors, and every item was chipped up, I would save hours every week looking for stuff.

  30. Steven Roper

    Re: Devil's advocate says...

    "And assuming you don't put empty packages/containers back in"

    And you show me one bachelor's fridge that doesn't have at least two or three empty milk cartons, ketchup bottles, jam jars, butter tubs, or what-have-you...

  31. Intractable Potsherd

    Re: Devil's advocate says... @ Lost in Cyberspace

    "Now, forget about fridges for a sec - if every door in my house had RFID sensors, and every item was chipped up, I would save hours every week looking for stuff."

    This is something that could be the breakthrough for this stuff. Forget about bunging all this stuff on the internet - just keep it within the home so that it works for the individual. I'd be quite happy for a system like this, preferably with an ability to assess the height above the floor of the last movement, so I can at last prove that it wasn't me that moved it*!

    * Whatever the "it" is that can't be found.


    Re: Devil's advocate says...

    Most of the stuff I buy would not have an RFID tag for the same reason it doesn't have a barcode now.

    I also have the Tetris problem as well as the leftovers problem. Most of what's in my fridge are combinations of items that were not sold with bar codes.

  33. Martin-73 Silver badge

    Re: Devil's advocate says...

    Modify the song maybe? "Go stick a pig in your fridge" ?

  34. AutomationGeek

    Re: Devil's advocate says...

    Walmart in the USA already insist in every supplier using RFID. Their savings come from simpler product tracking.

    The consumer's savings come from a hassle-free life, less waste, reduced risk from eating out-of-date food, etc.

    I for one welcome our new Internet-connected Fridge overlords...

  35. kiwimuso

    Re: Devil's advocate says...

    @Steven Roper

    And how is it going to handle stuff which is so past it's 'Use By' date (assuming it even had one) that the contents have now turned to a nasty shade of grey/green. Milk still weighs much the same despite having turned mostly solid!

    Joke Alert, as the whole idea is a joke.

    I have a far better solution to the problem. I use my eyes and brain - what's left of it after reading this drivel.

    Sounds like a techos wet dream - except as an ex-techo, it doesn't even begin to register on my radar as a must have!

  36. malle-herbert Silver badge

    Well... let's see...

    A "smart" fridge could use some kind of system with multiple camera's

    that will do image recognition to identify objects placed in the fridge.

    Objects that have a barcode can be automatically scanned and the

    expiration date could be scanned as well.

    For liquids you could use sensors that detect the weight of the container

    so that when you take it out of the fridge and put it back in, the difference

    in weight can be calculated.

    (This could also work for non-liquids in some kind of a container...)

    For other foodstuffs the fridge could simply aks the user what it is and

    what it's expiration date is through some kind of touch screen interface.

    (Displaying the item on the screen and asking the user for a desciption...)

    And of course the system could learn from all of this by adding the unknown

    foodstuffs to a database so you don't have to do it again and again...

  37. I ain't Spartacus Gold badge

    Re: Well... let's see...

    What when I take several items out at once when cooking (as I try to be efficient when I'm organised), and then put them back in together? Which item lost how much weight?

    What about left-overs. I regualarly cook for more people than are present, in order to freeze leftover portions, so I have (actually edible) ready-meals available to me.

    How much in any fridge is staples, to be instantly replaced and how much is what's available or on offer? Not including parties. My fridge should always contain eggs, milk, limes, fruit juice, various condiments, yoghurt and cheese. Anything else depends on what I could find, or who's coming round for dinner.

    What about using multiple suppliers? I have a greengrocer at the end of my road. I try to buy all my veg from them, unless laziness kicks in and I'm in Sainsbury's anyway.

    What's the point of filling out only a third of my shop? Only about 30-40% of any shop goes in the fridge. The rest is cupboards, bathrooms, laundry cupboard.

    How much is this bloody fridge going to cost? And how long before it breaks down? It's got multiple cameras, multiple weight sensors. What happens when the bulb goes in the fridge, and no-one can be arsed to replace it, so the cameras can't see anything? I'm prepared to believe that the cameras will survive cold and condensation - but not the weighing shelves getting stuff plonked on them every couple of hours, and water dripped on them. And I'd worry for the touchscreen on the door too.

    In my opinion the answer is twofold. Online shopping is good. Have a tablet, wander round kitchen, look in fridge, freezer and cupboards, see what's missing, pick from list of favourites on website, order.

    But I still prefer to go to the shop. So for me, shopping list app on smartphone. When you use the last but one of something, take phone from pocket, add to list. After you've typed the first few letters, it auto-completes if it's something you've used before.

    The internet of fridges is still way too complicated.

  38. jonathanb Silver badge

    Re: Well... let's see...

    There is also the fact that if I'm going on holiday, I run down my stocks of perishable stuff before I go, and leave the fridge mostly empty, so I don't return to a fridge full of rotting food.

  39. Anonymous Coward
    Anonymous Coward

    Re: Well... let's see...

    For some reason my wife does the opposite so when we get back we have to throw all the spoiled food away

  40. Rosie Davies


    The article is pretty much sport one in considering the most baroque solution to the problem possible. The problem is that you have run out of something and need to replenish. Given that you are likely to be holding the thing as you run out of it a cheap-as-chips (sic) RFID tag that you can bonk against a reader in your kitchen (or cave for the more discerning Luddite) registering the item in the {phone|tablet|whatever} hosted shopping list would probably do the job. It would certainly save me from forgetting to add rarely purchased and essential items to the shopping list.


  41. Salts

    Re: RFID

    I was thinking along the same lines, but then thought all items have barcodes and barcode apps are available for smart phones and I could start scanning today, I think the problem for me is, I can't be arsed :-)

  42. Anonymous Coward
    Anonymous Coward

    Am I the only one who gets this?

    The milk carton only needs an RFID tag to say "I am here". Much like the barcode stickers with a wire loop in them, which already exist! When the carton has been removed from the fridge for more than, say, 10 minutes then we can assume it's not coming back and needs replacing.

    That's as smart as it needs to be.

  43. RISC OS

    Re: Am I the only one who gets this?

    Yeah... if you need a s hopping list telling you to buy stuff you still have

  44. I ain't Spartacus Gold badge

    Re: Am I the only one who gets this?


    I'm guessing you don't have kids. The milk doesn't go back into the fridge until someone sees it on the counter, and shoves it back in. Or in fact guests. Where the milk may be on the table by the tea and coffee stuff for 10 minutes.

    The same is definitely true for cheese, pickle, ketchup, fruit juice.

    Some sort of scanner by the bin and recycling might work though?

  45. Paul Hovnanian Silver badge

    Electronic Nose

    "The milk. That carton you bought 8 weeks ago. It really needs to be thrown out. Now."

  46. Anonymous Custard Silver badge

    Re: Electronic Nose

    You'd probably find if you opened the door it would walk/crawl/ooze out quite happily on its own and go lurk in a dark corner and scare the spiders...

  47. TRT Silver badge

    Re: Electronic Nose

    if $ageofmilk >> 3 weeks {




  48. Anonymous Coward
    Anonymous Coward

    Sorry, had to downvote you.

    You used the bitwise right-shift operator where you should have had a greater-than comparison operator. You can't expect to get away with that on a site like El Reg!

  49. Captain DaFt

    Re: Electronic Nose

    "You'd probably find if you opened the door it would walk/crawl/ooze out quite happily on its own and go lurk in a dark corner and scare the spiders..."

    Or start lurking way in the back of the fridge... and every time you open the door you hear it hunting for revenge, "Here, kitty kitty!"

  50. Steven Roper

    Re: Electronic Nose

    Or even worse, you discover it's formed an enlightened civilisation and started demanding political representation and civil liberties. I've had some growths in my fridge that have evolved to the point of attaining telepathic Gestalt superconsciousness...


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