The title is a bit bombastic but in my opinion it fits the trend I noticed here and which I think needs to be discussed.

To me it seems that many users here do not understand that some other users may have different design constraints than they do. Comments to this question made me start analyzing the problem. OP here complains that he can't find a two-pin phototransistor and one of our users claims that they are available at Digikey and believes that if OP can't get parts from Digikey, the question may be too localized.

Well, OK, that's one way to look at it. On the other hand, I believe that such attitude is simply bad engineering practice. In my opinion, one of the main objectives of an engineer is to make a working product with available resources, if that is possible.

Another interesting example of this trend are comments to this question. Again users can't accept that OP can't just buy a better part.

Yet another similar comment thread can be seen in this question where again some users can't understand that sometimes you just have to use datasheetless parts if you want to be competitive.

I have an example to post too:

Once I was recommended on this site to use 10 µF ceramic capacitors at input of voltage regulators. And where do we go to get them? Digikey of course! They're a big huge distributor and they have millions of articles in stock. The capacitors I linked look interesting and not too expensive so I'd probably buy 50 or maybe even a 100 of them and be stocked for a while. That's $14 for a 100 pieces.

So let's take a look at Digikey's website for my country. In the middle o the screen, the second center picture from top proudly proclaims that the transport price from US to Serbia is fixed at $120. Well my $14 order just became $134 order and each capacitor now costs me $1.34 and that's before customs and forwarding fees. For $1.34, I could buy an entire simple voltage regulator here and more. If I take local administration into account, the single capacitor would be more like $2.5 to $3. For $2 I could get a PCB with a full-wave rectifier bridge, needed passive components and a voltage regulator. This disqualifies the capacitor even at optimistic price of $1.34 a piece as an economical solution to the problem.

Of course, the solution to this example would be to look for another distributor, but my idea in this post isn't to solve this particular problem but to start a discussion about the trend I've noticed.

What I instead believe is that we should try to form some sort of a guideline when it is acceptable to recommend a solution of selecting a new part and when we should believe OP that a better part can't be found.

So any thoughts about this?

  • 4
    \$\begingroup\$ I was going to answer this but I realized it would be more time effective to hire a consultant to write my post. \$\endgroup\$
    – Kortuk
    Jun 22, 2012 at 12:21
  • \$\begingroup\$ @Kortuk♦ Ploease let us know when you've hired one and when the expected project deadline is. :) \$\endgroup\$
    – AndrejaKo
    Jun 22, 2012 at 12:22
  • 1
    \$\begingroup\$ I just realized how much better the answer would be and you can get a consultant for nothing on freelancers.com so if it goes over budget I will just closed this as too localized. \$\endgroup\$
    – Kortuk
    Jun 22, 2012 at 13:00
  • \$\begingroup\$ @Kortuk♦ What a great idea. \$\endgroup\$
    – AndrejaKo
    Jun 22, 2012 at 13:52
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    \$\begingroup\$ sorry, have not had a time to write an answer yet, thought you might get a giggle out of this. \$\endgroup\$
    – Kortuk
    Jun 22, 2012 at 18:51
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    \$\begingroup\$ @Kortuk♦ Well I did. :) Take your time. Hopefully this question won't be closed by the time you have your answer ready. \$\endgroup\$
    – AndrejaKo
    Jun 22, 2012 at 18:57
  • \$\begingroup\$ I find your Digikey example a bit exaggerated. Surely you can find a local distributor with reasonable prices shipping to Serbia. \$\endgroup\$ Dec 16, 2017 at 20:35
  • 1
    \$\begingroup\$ @Dmitry Grigoryev Well, I do not. Because what local distributors have is not what Digikey has. Therefore, for me, answers such as "It's on Digikey" are not very useful. The whole point of the post was to show that if something is very easily obtainable in one part of the world, it does not automatically mean that it's available in another part of the world. Furthermore, finding the local distributors takes very long time, since they aren't actually very well known, and finding ones that are reliable takes even more time, meaning that many like to work directly with foreign distributors. \$\endgroup\$
    – AndrejaKo
    Dec 16, 2017 at 20:54

7 Answers 7


I know this is a personal issue and it looks like all the "damn lazy Americans" just want to buy premium parts from Digikey, but hear me out.

I don't have any problem with specific questions about specific parts, but it's really frustrating to have the OP say "Nice answer, but I can't use it because I actually have this other (significant) constraint that I forgot to mention."

Here's the thing - a lot of these questions don't have enough information to give an answer that would benefit the OP or even the community in general. This leads to a lot of people trying to guess what the real question is, and are trying to make a bunch of assumptions. There are problems with this setup:

  • We don't know if the OP has actually purchased a part, or is just planning on buying the part they mention. If they haven't bought a less desirable part, then perhaps they would find it useful to know that there may be better alternatives.
  • We don't know why the OP has chosen the part. Did they choose that TL084 because it was what they used in college, or because that's all they could find?
  • We don't always know where the OP is asking their question. Is their selection limited because they are in a foreign country or because they don't know where to look or what to look for?
  • We don't know whether or not their selection is limited. For example, you could probably get manufacturing quantities and prices on the vast majority of parts almost anywhere, but we don't know if the OP only has access to local hobby stores.

So now on to the problem that this causes - multiple answers for the same question, where users will pick the correct answer based on where they are located or what resources they have available, a.k.a. localization. This is probably the inevitable result of questions with a shopping component. I don't think we should get rid of these types of questions, but perhaps we should require more information up front. There isn't really an easy answer to this problem, which is probably why these types of questions are forbidden on other StackExchange sites.

If I want to help the poster, should I withhold my opinions because I don't know where the poster lives? Should I withhold my answers if I don't know what parts are available at the electronics stores in Belgrade?

For your op-amp example, I might recommend using an op-amp with a better offset voltage rating than the originally suggested TL084. If I compare the increased cost of the better op-amp to an offset compensation scheme that would be needed with the TL084, then I can find a cheaper solution with better performance. For manufacturing, no trimming of the input stage would be a huge plus, and I can even win in total price when I buy them as singles.

This answer would be completely inapplicable to your situation, if you can't get a decent/similar selection of op-amps. The cost of a trim pot could be significantly less than the cost of acquiring a better amplifier, in terms of travel costs or shipping/handling costs.

  • 1
    \$\begingroup\$ I have to say I get the most flags by users getting in arguments about question that in reality were poorly defined in the first place. \$\endgroup\$
    – Kortuk
    Jun 23, 2012 at 13:45

When it is acceptable to recommend a new part?

Unless the OP specifically states that they cannot change the parts used in the design, it is always acceptable to suggest any solution - including a new part - that will solve their problem.

When the OP explicitly states that they have to use a specific part, any answer that suggests a different part isn't ideal, but it's not a bad answer, especially since we're building a knowledge base for all engineers to visit in the future. IT may be that the "ideal" solution of switching a part doesn't solve the OP's problem, but it may make them more carefully consider their requirements, and it will help out future users with a very similar problem but who do not have that constraint.

The OP doesn't have to accept that answer, and can leave a comment indicating the poor fit for their particular application.

There is no need to flag, delete, or complain about answers that might be useful for future searchers.

So far your examples seem to show that the system of voting and comments is working. All except the altium footprint question have accepted answers, and the altium question won't be magically answered if we tell people they can't suggest a particular course of action, so solving this problem won't affect whether that question is resolved or not.

Generally, I'm opposed to restricting what types of answers can be provided unless the answer shows clear abuse of the system or misleads the OP. Engineering includes the ability to look critically at the requirements and question their necessity at times in order to improve the possible solution set. Restricting the answerers will only lead to fewer people willing to spend their time answering questions.

  • \$\begingroup\$ My consultant money was well spent. Great answer. I would only add that the reason users use digikey is because it is one of the larger suppliers here and if they have a part it is mostly assumed there is someone similar where you live, especially if they have thousands of options. Thanks for the great answer. \$\endgroup\$
    – Kortuk
    Jun 28, 2012 at 16:08
  • \$\begingroup\$ And users do often seem to forget that unlike a normal forum the post will help many more people the the asker. If you help 15 people it is worth it and for most of them relatively accessible parts can be assumed. \$\endgroup\$
    – Kortuk
    Jun 28, 2012 at 16:12

I would like to encourage everyone to stay playful. For instance, I work for a big company that produces yet-unheard-of top-notch products and during development, we get our parts as samples or from distributors; when choosing them, purchasing politics often play a bigger role than cost.


the majority of my most entertaining and educating hacking happens at home when I play with rules like obliging myself to the design constraint of using parts that I exclusively de-solder from junk boards found in my cardboard boxes.

Top secret info: My work involves safety circuits that need to behave in certain ways once a part fails, and another part fails. This stuff is not mass-market (not economical for IC manufacturers), and sometimes, the only solution involves 2N3904/2N3906 transistors with some additional passive components. Guess why they didn't fire me during the bad economy in 2008/2009? (Hint: Some discrete-component magic next to high-end FPGAs!)


When answering any design question, the most important thing I keep in mind is my priority of design constraints. Often my primary constraint is

  • BOM cost
  • NRE cost
  • calendar time
  • battery life
  • code complexity
  • system reliability

The same question can have vastly different answers given different design constraints. I often see answers or comments that totally disregard the questioners design constraints. For example, recommending a low BOM cost microcontroller when the question is clearly a one-off hobbyist or learning project. On the flipside, many questions will ask "How do I do X" without any context about the scope of the project, or what they are trying to optimize for.

Is there a way we can encourage more discussion of design constraints? Making good design tradeoffs is at the core of engineering!

  • 1
    \$\begingroup\$ Knowing the design constraints is important, but you can't always trust the OP to tell you the real constraints. When someone says they can't get a part, it usually means they haven't looked around properly. People asking questions often get hung up on particular solutions when they should be only telling us their true requirements. And no, I need to use a 555 timer, 2N2222A transistor, or 741 opamp aren't likely true requirements. Drilling down to get the real requirements is also part of engineering. \$\endgroup\$ Jun 22, 2012 at 14:51
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    \$\begingroup\$ Your observation, while valid, is really a different topic from what this question is about. \$\endgroup\$ Jun 22, 2012 at 14:56

To me, the dialog:

Q: "How do I do X?" A: "Do Y."

is about as useful as

Q: "How do I get to X?" A: "I wouldn't start from here."

And yet, that seem to be a popular type of answer.

Look, it will frequently happen that someone asks a question, but we require more information before answering. It's surprisingly difficult to ask a question so perfectly that it requires no clarification at all.

Writing a question is a little bit like writing software. You think you've covered every eventuality that will matter, but something always comes to bite you. Sometimes the problem is that the answerer suggests a part you can't get. Sometimes they suggest you do something entirely different.

I think this problem is part of a more general case.

I'm not sure what I'm talking about. I'm very tired and haven't slept. Maybe there was some sense in this answer.

  • 3
    \$\begingroup\$ "Do Y" without explaining why (no pun intended) is useless. When I read "I wouldn't start from here" I expect to read in the next sentence why not. And then I would have no problem moving on to "Y". I might refer to "X" a few times: "You see, this works, if you had chosen for X you would have had this or that problem." \$\endgroup\$
    – stevenvh
    Jun 24, 2012 at 7:22
  • \$\begingroup\$ Sometimes telling people to do something different from what they asked about is a valid answer. All too often, people come here pre-supposing a particular solution that popped into their heads or for religious reasons. How would you answer "I am stuck by the side of the road with a flat tire. How do I change the tire with this soup ladle? That is the only tool in my car." \$\endgroup\$ Jun 24, 2012 at 16:25
  • 1
    \$\begingroup\$ So how would you change a tire if you would only have a soup ladle? \$\endgroup\$
    – m.Alin
    Jun 24, 2012 at 19:11
  • 4
    \$\begingroup\$ @OlinLathrop - Straw man argument. Practically nobody comes with that sort of problem. A better analogy would be "I have the wrong sized tyre wrench. Or my type wrench is too short to get enough leverage". Anyway, I bet MacGyver could do it. \$\endgroup\$ Jun 24, 2012 at 22:46
  • \$\begingroup\$ @m.Alin: The answer is obviously to stop wasting time trying to do it with the soup ladle since that won't be successfull. Instead of wasting 2 hours futzing with the soup ladle and getting nowhere, you can spend it doing a number of other things which may lead to success, like calling someone, walking to a gas staion, flagging down a motorist, sending a smoke signal, etc. The point is, the correct answer is Don't do A as you asked, do B, C, or D instead". \$\endgroup\$ Jun 25, 2012 at 12:42
  • 7
    \$\begingroup\$ I think that this here is a classical false analogy. To disqualify the (rare) questions where the original idea is indeed impossible, I placed the if that is possible part in the third paragraph. A much better analogy here would be user asking how to change the tire using the jack and the wrench from the cars toolkit being told that he needs a pneumatic powered wrench to remove the screws and a power lifter to lift the car, since using the jack and the hand-operated wrench would to too inefficient and that any serious repair shop would never use hand tools for job such as this one. \$\endgroup\$
    – AndrejaKo
    Jun 25, 2012 at 17:18
  • 3
    \$\begingroup\$ @AndrejaKo The real issue for me here is that both Olin's situation and your situation often occur and people often take it as the other situation. \$\endgroup\$
    – Kortuk
    Jun 27, 2012 at 14:27

I think that this all comes down to the biggest dilemma with Q&A sites and especially Stack Exchange sites: The original post/question does not show extensive research and/or is not complete.



  • Like W5V0 said in his answer, if the OP forgets to mention things, we are forced to make assumptions. If the OP must use a specific part, its their job to specify that in their post, and our job to respect that by not offering alternatives to a given constraint. If something isn't specified, however, answers have every right to suggest other parts/methods, especially if it is more cost effective or time efficient.

To put this in the context of buying parts from Serbia:

  • Research: If the OP only ever looked at Digikey, saw the ridiculous prices, and then came straight to this site for help, that does not show enough research. If he looked around, like Olin mentioned, maybe he would've seen these other sites that offer affordable prices, and perhaps not needed to make the post (but... see below)
  • Completeness: If they were locked into using one part (not because they didn't research, but for some uncontrollable circumstance), then they should say so. If the OP makes this clause, we must respect that. Bashing their constraints isn't constructive.

To summarize my thoughts:

  • I think above all else, an "engineering solution" is one that solves a problem with high priority to cost and time efficiency.

  • It is the original poster's responsibility to do thorough research, and to state their question completely.

  • If an "answer" provides an engineering solution to a problem, and stays within the problem's constraints listed, then it is completely valid.

  • \$\begingroup\$ No, we should not automatically believe when someone says they must use a particular part without a good reason. We have every right, in fact it's good engineering, to question assumptions and requirements. Half of engineering is getting the requirements right, and people that come here asking about a solution often don't know enough to think out the true requirements correctly. So we should not take a OP's requirement at face value. We can either ignore it or try to drill down to the true requirements, whatever we have time and inclination for. \$\endgroup\$ Jun 29, 2012 at 17:12
  • \$\begingroup\$ @OlinLathrop I agree with you. That's why comments exist on these sites, to get clarification on things, to question/confirm the OP's constraints. My thoughts are with regard to a final answer to the OP, which should not make assumptions, or at the very least, note what assumptions are being made. \$\endgroup\$
    – kevlar1818
    Jun 29, 2012 at 17:22

When someone says they "can't get" a part it's most likely uninformed whining and/or laziness. Sometimes it seems this is said to force the answer to be particular part because that's what they want the answer to be for some silly religious reason they know they'd get laughed out of town for if they were honest.

I know for a fact that parts are readily available in Serbia, which you used as example. I have most of my products manufactured in Serbia (Data Tehnik in Novi Sad), and they can get anything I specify. DigiKey is one of the worst distributors for shipping to out of the way places. Mouser, for example, is much better, and then there are always local distributors. Djula at Data Tehnik can sometimes get equivalent parts from his local distributors I don't have access to for less than my distributors. It works both ways, but on the whole it is about even.

So unless you're at a antarctic research hut in the middle of winter or on the international space station, don't give me line of crap about how you can't get a part. And I don't want to hear how DigiKey charges a leg and three fingers to send a package to your town. Maybe that's true of DigiKey, but there is a wide world of other suppliers out there. DigiKey is known for being difficult in this area, so don't use them. I just don't believe there isn't a way.

  • 5
    \$\begingroup\$ Actually I just used that as an illustration (as I pointed out), since in first the question I linked, Digikey was mentioned as an authoritative source of what is considered available and what isn't and I explicitly stated that yes, I'm aware that there are other distributors and yes, that would be the potential solution to the problem showed. Still this doesn't the main point: What should be done when user asks for a way to "engineer away" a problem and is instead shown how to solve the problem by replacing a part (I do agree that in some situations that is the only answer). \$\endgroup\$
    – AndrejaKo
    Jun 22, 2012 at 14:17
  • 1
    \$\begingroup\$ @AndrejaKo: Again, my point is that the part that easily solves the problem is available. You are aware that there are better distributors than DigiKey, so your example is completely irrelevant. I simply don't believe that in most cases a part really is unavailable. \$\endgroup\$ Jun 22, 2012 at 14:47
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    \$\begingroup\$ @Olin, Your assembly shop can find parts at prices comparable to Digikey. Does that mean for certain those local distributors will do business with hobbyists on the same terms? \$\endgroup\$
    – The Photon
    Jun 22, 2012 at 16:24
  • 1
    \$\begingroup\$ @ThePhoton: What is this fixation on DigiKey? No I wouldn't want them getting things for DigiKey prices, that would be too expensive. When they get things from the US for us it's usually Mouser, and they have their local sources too. I don't know anything about the local sources, but sometimes our quantities are small too. I expect singles will cost more, just like they do all over the world. \$\endgroup\$ Jun 22, 2012 at 16:42
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    \$\begingroup\$ -1: inflammatory language. I'll undo my downvote if you remove the "whining" "laziness" and "don't give me that line of crap" stuff and replace it with more professional language. \$\endgroup\$
    – ajs410
    Jun 22, 2012 at 18:42
  • 8
    \$\begingroup\$ @OlinLathrop, Digikey, Mouser, even Jameco, whatever. My point is that a distributor (not an American distributor but a local distributor) in Serbia/Turkey/wherever might not be as friendly to hobbyists as the sources we have in the USA. Just because your manufacturer can use some local distros (with prices similar to what we get from our local distros) doesn't mean they're available or will sell on reasonable terms to hobbyists. \$\endgroup\$
    – The Photon
    Jun 22, 2012 at 19:02
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    \$\begingroup\$ If you remember some time ago, distributors like Digikey and Mouser were not nearly as hobby-friendly as they are now. They had high minimum orders, poor shipping terms, etc. Hobbyists had to shop at places like Jameco or Radio Shack and pay 2x, 5x, 10x as much. Not living in a "remote" part of the world, I don't know that the local distros there aren't still like the big guys were here once upon a time. \$\endgroup\$
    – The Photon
    Jun 22, 2012 at 19:05
  • 7
    \$\begingroup\$ There are times when you want to make the project now, with whatever components you possess, instead of having to wait a couple of days for an order to be delivered. Often you end up paying more for the transport than for that few components you needed. \$\endgroup\$
    – m.Alin
    Jun 22, 2012 at 20:51
  • 11
    \$\begingroup\$ Take a chill pill. And don't tell me you cant get them where you live. \$\endgroup\$ Jun 23, 2012 at 22:11

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