Black box – What is going on here?

Blackbox
Ok, Makers – help a teacher out – what the heck is this? Fredrick writes – I am a middle school science teacher in Oakland, CA. Several years ago, I encountered a lesson plan describing a “Black Box” activity. The person who provided the descritption of the box wasn’t able to get the plans for building the box. For the past three years I have sent several request to engineers, researchers, and science teachers asking for a possible understanding of the hidden mechanism of the Black Box. I have included a copy of the plans and a description of the item. I would be in your debt for any assistance you may be able to render. Not only would you be doing a great service for myself and my students (about 150 of them), but also the many teachers (and their students) I collaborate with throughout the bay area.

Post up in the comments, if anyone can figure this out we’ll send you out some MAKE goodies…

108 thoughts on “Black box – What is going on here?

  1. The two most simple answers, both hinge on one premise: the box is pre-filled with a number of black and white balls.

    The balls being dropped in either weigh different amounts and activate a sorting mechanism based on weight (the slight time delay mentioned would seem to support this theory), or the balls are sorted on color via a “simple” photosensor. The electronics for the latter could be easily powered for days with a 9 volt battery. Either solution could be built with low to moderate complexity.

    MY question to you: Why is this unit so intriguing? Is there some education value that I’m missing, or is just a curiosity? Why would you want to duplicate it?

  2. This is actually a magic trick that is popular with performers for children; unfortunately I am drawing a blank on the name of it. There are similar tricks to this one but I have seen this particular one once up close. I, however, wasn’t permitted by the performer to inspect it closely. From my own foray into performing magic I know of similar tricks (non-electronic)that use either different weight balls or slightly different size balls and of some electronic ones as well. As BrK mentioned, the tricks are typically preload with balls and the addition of each new ball in the top triggers a release mechanism. I will try to remember the name of this trick so I can try and find better info on its particular workings or if you like I can suggest a few solutions based on my experiences.

  3. A mechanical system would most likely differentiate by size, weight, or magnetism. Without more information it is also possible it has a preset order. The mechanics may have a windup or electric motor to drive it.

    If it is electric, it may need no internal seperating system. Someone could tell it remotely what to drop.

  4. I agree its definitely a magic trick. It’s funny when people come up with explanations for tricks they are always way more complicated than the trick turns out to be. And when you learn the secret you can’t believe you didn’t think of it. This one could be related to the ball return on pay billard tables, you know the cue ball always comes back out but the others don’t (the cue ball is slightly bigger). But it sounds like a simpler mechanism could also explain it. It sounds like the operator alternated black then white, the story doesn’t say if he ever put two of the same colour back to back. So the mechanism wouldn’t have to distinguish colour. it would just have to be preloaded with a white ball at hole 1. The first ball being black would bump the ball from hole 1 and stop at whole two, the next ball is white and would bump the black ball from 2 and stop at 3 etc. Of course you still have to design the mechanism but that simplifies it a bit.

  5. Another explanation. These boxes are often used to stimulate creative thinking. The story reminds me when I was in 3rd grade (over thirty years ago) and the teacher smiled as we all begged to know how the box worked. The following: http://www.accessexcellence.org/AE/ATG/data/released/0332-RevaBethRussell/index.html
    although a different “flavor” of contraption, suggests that your box, too, may involve an element of sleight of hand.
    Interestingly no plans are ever available and no one is ever allowed to see in the box during these demonstrations.

  6. I’ve seen a similar demonstration using water. Pour water into the box and you would sometimes get out red, yellow, or blue. The trick was the funnel went into a 90 degree angle and the user would secretly rotate the funnel so it would pour into one of three different funnels filled with paint.

    BrK – This is one of those “nature of science” types of demonstrations. Students have to make inferences and perhaps test their hypothesis by building or sketching their ideas. Usually they are never shown the correct answer since in science we can never just open up the box and look.

  7. I am not sure about the alternating holes but the (commonly red) spongeballs that magicians use could be easily hidden and swapped for a ball of the opposite color when inserting into the box. This would have to be a sleight and would probably be visually sensitive to viewer angle.

    Even better, I suppose you could also use a type of color changing paint on balls in such a way that when heated (by your hand) they would turn one color, and when inserted in the box top dry ice would cool the ball and thus change the color. By having both balls that are white and black when warm the box would produce opposites every time. Obviously dry ice would be necessary because it doesn’t simply melt. This method could also be combined with some simple mechanical incremental sorting device (ask a manufacturing engineer) to put the balls in the correct chutes 1-2-3-1-2-3-…. I suppose the only hole here is finding a pigment that is white when cool.

  8. A possible anwer to the “what’s the value” thing: Just to find the most simple way to build the functionality inside such a black box. Simplicity and ideas, this is what “making things” should be about. You can allways do things with brute force (ie put a computer inside the box). But that’s no fun… It’s like solving plain geometry problems using numerical computation on a supercomputer. And what’s the value of wasting time solving a geometry problem? You exercise your brain. It looks like this became a waste of time for many of us. But not for a teacher, and this is a great thing.

  9. Brian enigma had it right–

    The flip-flop can not only be configured to direct the balls to three exits, but a fourth flip flop (before the others) can also be used to trap a ball by blocking a switch-back until the next ball is dropped to toggle the flip-flop in the opposite direction.

    I made a crude drawing in pdf format– any way to post it?

  10. Brian enigma had it right–

    The flip-flop can not only be configured to direct the balls to three exits, but a fourth flip flop (before the others) can also be used to trap a ball by blocking a switch-back until the next ball is dropped to toggle the flip-flop in the opposite direction.

    I made a crude drawing in pdf format– any way to post it?

  11. Brian enigma had it right–

    The flip-flop can not only be configured to direct the balls to three exits, but a fourth flip flop (before the others) can also be used to trap a ball by blocking a switch-back until the next ball is dropped to toggle the flip-flop in the opposite direction.

    I made a crude drawing in pdf format– any way to post it?

  12. Well, I am going to assume that we aren’t being tested ourselves…

    Here is a link to a report that covers the topic and uses that very same graphic of the box and text.

    Research Report

    Hopefully I’m not ruining the fun.

  13. Well, I am going to assume that we aren’t being tested ourselves…

    Here is a link to a report that covers the topic and uses that very same graphic of the box and text.

    Research Report

    Hopefully I’m not ruining the fun.

  14. Well, I am going to assume that we aren’t being tested ourselves…

    Here is a link to a report that covers the topic and uses that very same graphic of the box and text.

    Research Report

    Hopefully I’m not ruining the fun.

  15. Damn, somone should really fix the comment posting system here. I don’t post on many stories because of all the problems.

    Some interesting points, the more that I think about it, the more likely it is that this is a simple mechanican mechanism.

    I doubt it’s the color-changing paints, although I personally have played with some magic trick ideas using those paints. Here in my office, I have 3 boxes of sample kits from Alsa paints with some of their color-changing products. It’s cool stuff, but hard to get a reliable outcome every time, which is a key component to any magic trick. You want the audience to be able to inspect the balls, for example.

  16. The “dependency” of white balls producing black balls is an illusion. All you need is to preload a sequence of balls to come out and make sure you select “at random” the inverted sequence to go in. To remember the sequence you could just thing of a 4-digit hex number and have a black ball=binary0 and white = binary1.

    Careful about leaping to conclusions about causal relationships!

  17. The way I think I would do it would be to use a light sensor. That would tell me if the ball was white or black. Then you can have an electronic switch controlling the hole gates based on the light sensor. If you pre-load both colors of ball and put logic on the switch to release the gate for the opposite color ball, you get the alternating effect. You just have to make sure that the ball you just put in will fall into the previous ball’s spot and to never put more than one of the same color ball in a row, unless the ball holder has space for more than one.

  18. I have to agree with BrK on questioning what the educational value on this is, other than making a kid think about how he would manage it. However, if the kid doesn’t have some electronics or mechanical knowledge already, you’re kind of wasting his time and shouldn’t go for the black box approach.
    I didn’t think about the weight of the ball, I guess that would work just as well as a light sensor if the black and white balls both had specific weights that were different from each other.
    However, with the black box approach, there’s just too much that can be faked as far as causal effects. I’d recommend making the front side of it glass so you can see into it and you can talk to the kids about each operation that’s going on inside.

  19. This reminds me of the April Fools joke Scientific American published many years ago, a fake article about archeologists who found dug up rudimentary logic gates from an ancient aboriginal culture.

    The article described these logic gates as boxes with 2-4 ropes protruding from holes, and an internal mechanism of pulleys. The different types of mechanisms representing basic logic functions — AND, OR, XOR, NOT, etc. When a rope or two was pulled (representing a logic “one”) on the ‘input’ side, the protruding ‘output’ rope(s) on the other side would pull or not pull depending on the logic. Combining multiple units could produce basic computing elements — basic math, counter, etc. Even though the article was fake, the concepts were accurate.

    I think I was 14 at the time, and got so excited that I showed my science teacher, who pointed out that it was a joke.

    Getting to my point… For everyone who is wondering what the educational value of this black box is, consider this: when I was a young teen and first read that Scientific American article, it captured my imagination as I worked out how the various components worked, contributing to my creative engineering skills. That was 20 years ago, and it no doubt play a small fundamental role in my successful software engineering career.

    Don’t underestimate mental exercises like this.

  20. BrK I think already has a pretty good explenation, however I doubt that it is weight it’s more likely to be colour. 30cm*50cm can house a lot of balls because the mechanism shouldn’t be really big. I believe it just looks at the colour of the ball puts it in the right storeage place then takes one from the other colour’s storage and puts that out the right hole. The release mechanism is just a simple repeat program I’de say. I believe this could be done with a simple Lego Robotics Kit.

  21. BrK I think already has a pretty good explenation, however I doubt that it is weight it’s more likely to be colour. 30cm*50cm can house a lot of balls because the mechanism shouldn’t be really big. I believe it just looks at the colour of the ball puts it in the right storeage place then takes one from the other colour’s storage and puts that out the right hole. The release mechanism is just a simple repeat program I’de say. I believe this could be done with a simple Lego Robotics Kit.

  22. BrK I think already has a pretty good explenation, however I doubt that it is weight it’s more likely to be colour. 30cm*50cm can house a lot of balls because the mechanism shouldn’t be really big. I believe it just looks at the colour of the ball puts it in the right storeage place then takes one from the other colour’s storage and puts that out the right hole. The release mechanism is just a simple repeat program I’de say. I believe this could be done with a simple Lego Robotics Kit.

  23. BrK I think already has a pretty good explenation, however I doubt that it is weight it’s more likely to be colour. 30cm*50cm can house a lot of balls because the mechanism shouldn’t be really big. I believe it just looks at the colour of the ball puts it in the right storeage place then takes one from the other colour’s storage and puts that out the right hole. The release mechanism is just a simple repeat program I’de say. I believe this could be done with a simple Lego Robotics Kit.

  24. Don’t want to be rude, but as far as brainteasers/educational, this is in the So What category.

    Now here’s one of my black box faves, which I actually built (left it natural wood color though): a featureless box (about 6″ X 4″ X 2″, more or less, not a critical factor) with an off-center peak on top, (although that’s not critical it is a clue to the shape of the guts inside, I should have built it completely cubical), a couple of AA cells plug in to a jack (or AAA cells, not a critical factor), with the batteries plugged in it makes small electric motor noises, if you put it on the table it “shuffles” (best I can describe it) along in one direction, faster if there’s slack in the battery wires, slower if it has to drag them; if you put it on low friction surfaces it just sits there, if you hold it in your hand there is no discernable force except normal gravity. If you reverse the batteries…. it still travels in the same direction. ‘Splain what’s in the guts of the box. Eschew complicated ideas, it’s pretty simple.

  25. OK, several people have hinted at this – I’ll just add my two cents worth.

    The white and black balls need to be only slightly different in size. When put into the box, they both pass over a hole that is only large enough for the white balls to fall into. Thus, white is sorted from black (just like the coin mechanism in a soda machine). As the balls pass through their respective paths, they hit a microswitch with a wire trip, and that “releases” one ball of the opposite color for delivery. Again, think of a soda machine. Finally, the down ramp has mechanical gates, with one open at a time. As a ball passes through the open one, it hits a switch that closes the current gate and opens the next gate.

  26. I think, as Madra pointed out, we are being tested here as this was used as a thought exercise in another report.

    A couple things to point out:

    1) Such boxes exist for magic show performances and have for a very long time (ie. pre-electronics). For many tricks, such as these, the answers are typically ridiculously simple. Most Makers should know that, unless you are Rube Goldberg, the simplest answer is usually the best answer. From experience I can tell you that a couple dollars worth of wood dowel, some elmer’s glue and a sandwich (I get hungry you know…) can achieve a similar effect.

    2)This “Black Box” is an excellent teaching tool. On its own the “box” can do little more than inspire wonder and curiosity in its viewers (which I might add is key component in science, technology and the whole idea of making things yourself). However, when presented by a creative teacher it can be used to demonstrate numerous lessons, limited only by the teachers imagination. This box can be used to get students thinking “outside the box” and about what is inside. Plus it’s just cool to watch… have you ever tried to keep a bunch of kids occupied for more than a few minutes?

  27. After reading all the comments, it looks like this has already been hinted at, but here is a design I managed to throw together in paint (I know it’s bad… meh). The premise is that when a ball gets dropped in it gets trapped and at the same time releases a different ball of another color. Then it’s a simple matter of a few flip-flops to make the 1,2,3,1,2,3 sequence. The problem with this design is it requires you to alternate the color of ball you drop into the box (I.E. you can’t put in the same color twice in a row).

    Here is the design: linky!

    Red 1’s are flip-flops, the blue 2 is a sort of sea-saw type lever, the green 3’s are gates that can be opened by pulling them down (with a spring or elastic band to pull them closed when there is no longer anything holding them open), and the purple 4’s are just pulleys or wheels. (There is another lever/switch at the bottom that I forgot to mark, but it’s pretty obvious).

    When a ball is dropped in, it will pass by a preliminary flip-flop that will drop it down the opposite shut that the previous ball took. At the bottom is a lever that when flipped will open the gate to the previous balls holding area, at the same time closing the gate preventing the ball you just dropped in from escaping. The ball that was just released will drop by a series of more flip flops that will direct it to either hole number 1, 2, or 3. The first hole has a lever over it that is tied to the first flip-flop in the sequence, so when a ball drops out of the first hole the first flip-flop will reset (otherwise the sequence would be 1-3-2-3-1-3-2-3-exc.).

  28. As makers, I think we have a tendency to accept the premise that this is a device that actually processes the inputs as described, and come up with an electronic sensor/actuator solution. Of course we know now that this is just a thought experiment, and no such box existed, but if I were to quickly make one of these to test kids, however, I would probably take a simpler route and either release the balls via remote controlled servos based on what I saw go in, or cut a hole in the table and bottom of the box and place a person underneath to feed the balls out.

  29. Here is another design (also previously mentioned) that will allow you to drop in the same color ball twice in a row, but one color would need to be bigger.

    Here is the design: linky!

    In this picture the green 3 isn’t a ramp, but 2 wooden dowels (or metal rods, whatever) that are spaced apart just far enough to let one color drop trough, but hold the other.
    Number 5 represents 2 wheals with a notch cut out of them that the colored balls can fit in. When a string attached to a lever (marked # 2) is pulled, the wheel rotates just enough to drop a single ball down to the ramp below. In this way only one ball is released at a time.

    When you drop a ball in the top it will go in one of two directions depending on it’s size, if it’s larger it will go to the right, trigger a lever that will release one of the balls held in the ramp to the left, and fall into the holding ramp on the right. The rest of the mechanism is exactly the same as the design I posted previously. If the ball is smaller it will fall trough the dowels/rods and go to the left, hit a switch releasing one of the balls on the right, and fall into the holding ramp on the left.

  30. It is possible, and not even that difficult to do.

    1) The balls are heavy.

    2) One colour (say, black) is magnetic.

    3) A steel bar on one side of the entrance trough pulls the black balls to the side, and into a (slightly) uphill hole, while the white balls fall into another hole. From there, the mechanisms are the same.

    4) Each ball rides down to its hopper on a conveyor, which turns a disc below the opposite colour’s hopper, releasing a single ball.
    5) The conveyor also turns a disc with a single hole that rotates over tubes leading to the three different exits.

    6) Balls from either hopper drop onto that disk, then go through each exit in turn.

    Essentially, it is a double gumball mechanism, powered by the weight of the dropped ball. The only hitch would be how much energy would be needed to turn the mechanisms and overcome friction. I guess a hollow steel ball filled with lead would help, and/or a goodly drop onto the conveyor. As well, making the conveyor longer, thus lowering the gear ratios needed to rotate the disks, would increase efficiency.

    Thnik about it!
    DeadlyDad

  31. Sorry. I realized something after (of course) I posted. The black balls aren’t magnetic, just have a steel shell. The steel rail is. The White balls are just lead. Both are coated with enamel or whatever.

  32. Could always just make a robot, with a light sensor to detect white vs black, and a bin of white balls and a bin of black balls, and drop it into the right one. Then, pop out an opposite-colored ball, and put it on the next sequential chute. Though, I like Hungry_Myst’s plan better.

  33. gzuckier said:

    if you put it on the table it “shuffles” (best I can describe it) along in one direction […] ‘Splain what’s in the guts of the box. Eschew complicated ideas, it’s pretty simple.

    May it be just a motor with an “unbalanced weight” like in cellphones ?

  34. Jesus. Could makezine’s warez suck more? Three minutes of wheelspinning after each post attempt, but, of course, it turns out it was posting each time whether or not I stopped the loading.

    Well, pretend I was making a hilarious joke about birds and three different slots for little marbles to fall out of.

  35. Hello all,

    I would like to first thank all you who have taken the time to respond to my request for help. For a few years I have posted on educational sites and gotten no responses. Now, I have over 50. Subscribing to make was definitely a great investment (especially since I not the most mechanically inclined of teachers).

    No, this was not a prank to test the mental or mechanical acuity of those who subscribe to make. I actually would like to make such a box for students. Some have asked “Why is this unit so intriguing”. Of course there are other, much less sophisticated activities involving Black Box activities. Unfortunately, many of my students are bored by these activities. It’s kind of hard to hook a group of kids to excitement and wonder of science when you are using so very low-tech equipment (to be honest, is boring to teach much less be inspiring). Our children are surrounded by a highly sophisticated and technological rich environment, except when they are in a classroom. I just want an activity we can start off the year that really captures their attention (for middle schools a majority of the battle is keeping their attention).

    I thank you again for all your help. I have much to digest and see if I can build this in the next two weeks. Now I have to find a good supplier of materials to build this box. If anyone has free time and a workshop (in the bay area), I would be willing to pay for dinner for some guidance and workspace.

    Frederick

  36. Hello all,

    I would like to first thank all you who have taken the time to respond to my request for help. For a few years I have posted on educational sites and gotten no responses. Now, I have over 50. Subscribing to make was definitely a great investment (especially since I not the most mechanically inclined of teachers).

    No, this was not a prank to test the mental or mechanical acuity of those who subscribe to make. I actually would like to make such a box for students. Some have asked “Why is this unit so intriguing”. Of course there are other, much less sophisticated activities involving Black Box activities. Unfortunately, many of my students are bored by these activities. It’s kind of hard to hook a group of kids to excitement and wonder of science when you are using so very low-tech equipment (to be honest, is boring to teach much less be inspiring). Our children are surrounded by a highly sophisticated and technological rich environment, except when they are in a classroom. I just want an activity we can start off the year that really captures their attention (for middle schools a majority of the battle is keeping their attention).

    I thank you again for all your help. I have much to digest and see if I can build this in the next two weeks. Now I have to find a good supplier of materials to build this box. If anyone has free time and a workshop (in the bay area), I would be willing to pay for dinner for some guidance and workspace.

    Frederick

  37. Hello all,

    I would like to first thank all you who have taken the time to respond to my request for help. For a few years I have posted on educational sites and gotten no responses. Now, I have over 50. Subscribing to make was definitely a great investment (especially since I not the most mechanically inclined of teachers).

    No, this was not a prank to test the mental or mechanical acuity of those who subscribe to make. I actually would like to make such a box for students. Some have asked “Why is this unit so intriguing”. Of course there are other, much less sophisticated activities involving Black Box activities. Unfortunately, many of my students are bored by these activities. It’s kind of hard to hook a group of kids to excitement and wonder of science when you are using so very low-tech equipment (to be honest, is boring to teach much less be inspiring). Our children are surrounded by a highly sophisticated and technological rich environment, except when they are in a classroom. I just want an activity we can start off the year that really captures their attention (for middle schools a majority of the battle is keeping their attention).

    I thank you again for all your help. I have much to digest and see if I can build this in the next two weeks. Now I have to find a good supplier of materials to build this box. If anyone has free time and a workshop (in the bay area), I would be willing to pay for dinner for some guidance and workspace.

    Frederick

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