puzzle: how many capacitors are in the SMD box? - Page 1
Forum section: electronics / general

author: FrankBuss
author_rank: Unknown
timestamp: September 06, 2014, 04:13:57 pm
content: Got a very nice new cam, just testing:Answer fast without counting! So far anyone I asked underestimated the number of capacitors (0603 size, 100 nF).

author: Precipice
author_rank: Frequent Contributor
timestamp: September 06, 2014, 04:32:10 pm
content: Maybe 800, or 'slightly fewer than you need'?(I've finally got annoyed enough about buying duplicate reels of parts to do a bit of an inventory. Just over 1000 reels of resistors so far, no wonder the house feels more like a stockroom. Next up, capacitors, That's going to be tedious, capacitor reel labels are ambiguous and unpredictable. Yay, a 30-digit part code. Thanks. )Anyway, I much prefer sample books to those little tubs, less chance of rogue parts and spillages

author: Artlav
author_rank: Frequent Contributor
timestamp: September 06, 2014, 05:25:45 pm
content: One short of what it was when full.

author: c4757p
author_rank: Super Contributor
timestamp: September 06, 2014, 05:45:13 pm
content: I'll guess 800-1000, if that's not too wide of a range.Quote from: Artlav on September 06, 2014, 05:25:45 pm

author: TheBorg
author_rank: Frequent Contributor
timestamp: September 06, 2014, 05:53:02 pm
content: I'd venture to guess 1500.

author: zapta
author_rank: Super Contributor
timestamp: September 06, 2014, 06:03:04 pm
content: 4000.20 L x 20 W x 10H

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 06, 2014, 06:38:06 pm
content: Seems low. I could try to calculate the tilt between visual plane and plane of the box top, and get a better estimate for the height. Or I could look up packaging like that and see what the standard sizes are (1000?).Looks like a terrible way to store chip caps anywayTim

author: mariush
author_rank: Super Contributor
timestamp: September 06, 2014, 07:05:00 pm
content: It's complicated because the capacitors don't seem to be stacked neatly. there's lots of air between them, so it's pointless to try to determine the number based on volume and size of individual caps.If I were go guess, I'd go with multiples of various quantities that are commonly available to order.... visually there don't seem to be more that a few layers stacked so 100 seems too low, 250 would be possible, 500 would still be ok and 1000 is too much. The decrease value by 1 and maybe remove 20-50 that were probably used.

author: gibbled
author_rank: Regular Contributor
timestamp: September 07, 2014, 03:39:46 am
content: 2000.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: September 07, 2014, 03:50:43 am
content: was going to say 800 but it's taken.So 700

author: miguelvp
author_rank: Super Contributor
timestamp: September 07, 2014, 04:01:39 am
content: 500 - 1

author: wagon
author_rank: Frequent Contributor
timestamp: September 07, 2014, 04:43:00 am
content: 42

author: rs20
author_rank: Super Contributor
timestamp: September 07, 2014, 04:53:21 am
content: Quote from: mariush on September 06, 2014, 07:05:00 pmThe packing ratio is pretty much guaranteed to be between 0.5 and 1; so far from being pointless, the unknown packing ratio is probably the most tightly bounded value.

author: FrankBuss
author_rank: Unknown
timestamp: September 07, 2014, 05:10:13 am
content: Interesting estimates. To be honest, I don't know the exact numberIf someone wants to count it:Initially it was a reel of 1,000 capacitors, some got lost when I unreeled it (it is pointless to search them on the carpet) and since then I used a few dozen for populating prototypes of my C64 MIDI interface.

author: zapta
author_rank: Super Contributor
timestamp: September 07, 2014, 06:29:58 am
content: If one of them has the wrong value of 1 Farad (yes, 1F). How would you identify it with minimum number of measurements (DMM, ECR, etc)?

author: peter.mitchell
author_rank: Super Contributor
timestamp: September 07, 2014, 07:07:53 am
content: Quote from: zapta on September 07, 2014, 06:29:58 amit would have broken the box.

author: zapta
author_rank: Super Contributor
timestamp: September 07, 2014, 07:29:04 am
content: Quote from: peter.mitchell on September 07, 2014, 07:07:53 amSame size weight and appearance, just different capacity.

author: tautech
author_rank: Super Contributor
timestamp: September 07, 2014, 07:34:25 am
content: Quote from: zapta on September 07, 2014, 07:29:04 amEasy.http://www.advancedevices.com/Smart_Tweezers_LCR_Meter.htmSure they cost as much as a cheap DSO, but you will use them much, much, much more often.

author: miguelvp
author_rank: Super Contributor
timestamp: September 07, 2014, 07:46:15 am
content: VisiQuest says 843

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 07, 2014, 08:08:19 am
content: Quote from: peter.mitchell on September 07, 2014, 07:07:53 amNah, it's ceramic. It's 1F at 0.00V, dropping to <0.1uF at 0.01V.Tim

author: Cside
author_rank: Regular Contributor
timestamp: September 07, 2014, 08:38:48 am
content: Quote from: zapta on September 07, 2014, 06:29:58 am1. make 2 equal rows of caps in parrallel,2. measure capacitance of each row.3. Discard the row with the lower capacitance4. if remaining row has more than 1 cap,- Split remaining row into 2 equal rows, go back to step 2 and repeat.else- remaining cap is your 1FComplexity is n.log(n)

author: rs20
author_rank: Super Contributor
timestamp: September 07, 2014, 09:19:09 am
content: Quote from: Cside on September 07, 2014, 08:38:48 amI think you mean log(n) -- 1000 caps takes 10 iterations, not 10000.I suspect you can do even better by getting more than one bit of information per test...

author: FrankBuss
author_rank: Unknown
timestamp: September 07, 2014, 11:24:28 am
content: Quote from: miguelvp on September 07, 2014, 07:46:15 amInteresting. Does the program count it on its own, or do you have to train it first or do some complicated setup? Looks like an expensive program.

author: miguelvp
author_rank: Super Contributor
timestamp: September 07, 2014, 06:36:06 pm
content: Quote from: FrankBuss on September 07, 2014, 11:24:28 amI bought it years ago for work related things in image processing and it wasn't cheap and it's no longer supported or on sale by accusoft (it's a pity since it's very flexible) you program it by dragging and dropping glyphs and connecting them. Yes you have to tell it what to look for but setting it up is fairly easy.I made it look for rectangles within the image.It can deal with all kinds of data, it can do 3d reconstruction from slices and tons of other things. Can really work on any dimension so it applies to audio or anything.It all came from a program called khoros that was used in research and you can still find it around for Unix flavor OS. Also in khoros you can build your own glyphs in C, the commercial version VisiQuest was windows only and they offered the extra programmable features as an SDKbut a high price so I didn't purchase that part of it.The VisiQuest license is node lock to the computer's cpu id or maybe the ethernet mac address so I'm stuck to leave that system running XP.

author: FrankBuss
author_rank: Unknown
timestamp: September 07, 2014, 06:57:03 pm
content: Nice. I guess it visually marks all detected rectangles, so that you can verify the function? I searched for such an app but couldn't find one. Would be a cool program for smart phones. It should be possible to write one with OpenCV, but maybe not as good as VisiQuest.

author: Jorpy
author_rank: Contributor
timestamp: September 07, 2014, 07:18:53 pm
content: If enough people took a guess we could apply gaussian distribution and find the magic number that way O0The average of the current guesees is 1181.5 though..

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 07, 2014, 07:41:59 pm
content: http://en.wikipedia.org/wiki/Wisdom_of_the_crowdFor the sample size, that average probably isn't too bad.It's noteworthy that it gets worse if the crowd is able to see past guesses or trends!Tim

author: hlokk
author_rank: Contributor
timestamp: September 08, 2014, 08:36:15 am
content: My guess was 600-700 which I was pretty pleased with when I saw the results considering it was just a visual estimation and the height was unknown. (Didn't use the assumption that there were originally 1000 either).Quote from: FrankBuss on September 07, 2014, 06:57:03 pmI remember programming something that would do this back in my uni days. If you wanted to do it from scratch there's a few different ways you could do it, such as shape detection (hough detection and all). However, for that image I would be more inclined to do a hue mask so you get just the centres (it may work for the ends if you divide by 2 but they're touching more so). Then you do some noise reduction (like grow/erode or blur and cut), then you convert to an item number count (basically you run through the image and for each pixel see what its contiguously connected to and count the number of unique "pools"). Can be fun stuff.... if you're into that kinda thing :p Show someone a picture of Lena or a Mandrill and you'll know if they've done much image processingAnyways, the answer to the "how do you spot the large capacitor" in the least number of measurements is a variation off the "sack of fake gold" problem.What you do is arrange a number of capacitors in groups (parallel to add) then arrange the groups in series. Each group in the series has say 10 times the number of the previous, or as we're electronicsy, why not in factors of two for binary. Then the idea is you measure the capacitance and the large one will reveal itself in just one measurement by which significant bit the discrepancy is in. Although then you need further measurements to then narrow down exactly which one. Plus being a few orders of magnitude difference I'm not sure it would quite work as well as the original fake gold coin problem (which had coin weight/unit load as heavier than the difference times the number of bags you take coins from).Although if its really a 1F cap in a 1nF bunch or whatever then I'd say a more practical way would be to charge them all to a high voltage, then see which one sparks from the huge discharge. You'll know when you touch itAlthough if you chucked the caps on some thermal paper, the high farad cap would burn the paper leaving a telltale markI guess you could charge them slowly and the 1F would be not very charged, but that's significantly less fun. If you put them in a line, then charged them, then discharged them (so essentially only the 1F cap was charged) you could find the cap by measuring the voltage from the end to end (get the total) then end to middle and see which half had the voltage drop and then half that again and so on. So about 10 measurements. (pretty much as Cside said)But the modern solution is to send them to India and have someone test them for you for a few dollars

author: dannyf
author_rank: Super Contributor
timestamp: September 08, 2014, 11:06:23 am
content: You can estimate by weighing them.