I'm finishing up a design right now that involves our board interfacing with a piece of consumer electronics. We pull several connectors off their board, plug them into our board, and send jumpers back to the original. Plus there are various peripherals that get connected up. Our typical customer is a bit of a DIY, but by no means can we assume they have any electronics knowledge.

For the most part, each plug has a different pin count, so those are easy. But I have 4 different plugs with 4 pins and not much I can (or care to) do about that fact.

Do I just document well and assume they can read and follow directions? Or should I fool-proof it to some degree? The easiest and cheapest thing (besides documenting) is to color code the connectors. The ones we spec'd are available in white (cheap), black, red or blue (for a few cents more). But this doesn't stop them from physically plugging it in the wrong spot. Do we assume they're really stupid and spec differrent physical connectors? The only problem I have with that is - to me anyway - it looks funny. Big connector here, little one here, ohh, look this one's got wings! It just somehow looks, I don't know, messy. Finally, I can go expensive and get Molex or Tyco components that can be specified with different keying. But that takes us from a $0.02 JST to a $0.50 part and that isn't going to really go over well with the higher-ups.

I should note: This product has international appeal, so I can't guarantee the customer can read English well, and we don't have the budget (at least initially) to provide technical docs in multiple languages.

What would you do?

 

• Color coding and very good graphic illustrations can go a long way, especially when you cross the language line. Take a look at IKEA instruction sheets. Keying won't guarantee that someone won't try it force it to fit. Unlike "intelligence", there is no limits on "stupid ".

Ken

 

1) Nothing is foolproof. Fools are way too creative.
2) For any population of events, there will be a bell curve ranging from, "Piece of cake" to, "Where's the fire extinguisher". The best you can do is decide how much of that bell curve you are willing to eat the costs for and try to be clear where the limit is with your customers.

 

Similar to #12 my reply was always nothing is foolproof because fools are ingenious people.

Seriously? When you design something that interfaces with something else you also create adequate easy to follow work instructions. If the language barriers could be a problem you include easy to follow illustrations. Since you have not provided any illustration or pictures this is as good as it gets. Additionally in product design when I designed test stands with multiple connectors for interfaces I made sure each connector could only mate with the correct corresponding connector. So when a test stand with eight multi pin connectors was interfaced it could only connect one way.

 

I go for making it foolproof so that only the proper connectors will mate.

 

If there is no chance of serious injury, then I would go with the color coded connectors.

What would happen if the wrong connections were made? Ground a voltage line? Burn out a few resistors and ICs? Or nothing since only signals (with very little current) are being sent on the connections?

 

Here's a picture of the board as I have it right now.


I labelled the connectors A through J, and you'll notice a red letter X. I'll explain X first. We were going to have some expansion holes for the more avid tinkers, but today the decision to make them proper connectors was made, and that led me to posting here because those are going to be 2 four-pin connectors. That means A, J and X1/X2 are all 4-pin. Here's the breakdown:

A, J, X1/X2 - 4 pin
B - 5 pin
C, H - 9 pin
D , I - 12 pin
E - 6 pin
F, G - 2 pin

We can safely ignore the 5 and 6 pins because they are unique. Also the two 9 pins are safe because of physical properties of the board (they simply can't be plugged in to the wrong one due to cable length). I coded D red and I white because they can be mixed up.... sort of. D's cable could be plugged into I, but I's cable can't reach D... so it is fairly safe too. F and G are easily mixed up and catastrophic if reversed, so I've made them different sizes.

So really, my quandary comes down to the four 4 pins. You can see I made A and J different sizes but now that X1/2 are spec'd as 4's...

I guess its either specing yet another pitch connector (which really adds to the costs because you lose the economies of scale on things like crimp terminals) or I switch one to being something silly like a 7 pin.

Life really is simpler if I assume they can follow instructions But I guess I agree, I can't count on that. So its either expense and headaches now... or later.

 

If there is no chance of serious injury, then I would go with the color coded connectors.

What would happen if the wrong connections were made? Ground a voltage line? Burn out a few resistors and ICs? Or nothing since only signals (with very little current) are being sent on the connections?

Good question. If the 12-pins managed to get mixed up, that would be hospital bad. But I'm pretty sure they can't achieve that without scissors. I mean... they could plug D's plug into I and then power it up without finishing the connections, but SURELY they'd realize they can't get I's plug into D before they went and connected power, right? People can't possibly be dumber than that, can they? Lol. Mixing up F and G would damage the mcu in certain circumstances, so I made sure those were safe. A and J I'm not sure because it depends on what's on the other end for protection, but I wouldn't want to chance it. X1/2... it is in my design control, so thanks for bringing it up because I can make it safe if it isn't already. So maybe that's the ticket? Keep A and J on different pitches, and make X1/X2 inert if they are swapped either with themselves or with J. I think that's possible.


I'm glad I posted! You guys are making me think.

 

I decided not to be a pansy, and asserted my domina... err... polite opinion with the boss.

What I ended up doing was making SURE about the 12-pin by making one a different pitch, same as I did with the 2-pins. To resolve my quad 4-pin issue, I convinced them that those that want the features are fully capable of soldering so I've given them 0.100" pitch holes to work with (these people we're not concerned about killing because once they bust out the soldering iron, they're on their own). That dropped it down to one more 4-pin, so I just made it a 5-pin with one blanked. I then went ahead and made that a different pitch from the existing 5-pin.

So now, there should be no way for anyone to plug anything in backwards or swapped with the wrong cable. We now have two different pitches, which means a loss of economies w.r.t purchasing, but I figure it only sets us back a few cents per unit.... maybe 15c max. I told them 15c was worth not having to explain to a judge why I'm wearing an "I'm with Stupid" shirt in court.

Here's a picture of the board. Excuse the redacting... I'm not at liberty.

Thanks again for the help! I needed a sounding board.

 

There are numerous "right" answers and many of them can also be one of the many "wrong" answers on something like this.

Ideally, you would do a cost/benefit analysis taking everything into account, including the risk of someone managing to swap Cable A with Cable B and the consequences of doing so and then the cost of making it (nearly) impossible for them to swap Cable A with Cable B by using physically incompatible connectors. You look at how well clear instructions with stand-alone non-language illustrations reduce the risk.

Ideally these tradeoffs are presented to the appropriate level of management who then make the decision and things move forward.

In reality, of course, you can only make rough and quick estimates of most of these things and then a decision has to be made -- and the consequences of that decision lived with -- and often the "appropriate level of management" lacks the experience/skill/knowledge/balls to make a good decision and so someone that does not have the proper authority either has to make the decision -- at the risk of having painted a bullseye on their back if and when something goes wrong -- or just sticking their head in the sand and doing whatever the "powers that be" eventually sign off on and hoping that that gives them enough cover if and when something goes wrong.

It sounds to my like you have acted responsibly.

 

Hello,

As always, never underestimate the inventiveness of real fools.

Bertus

 

We frequently have to work within a requirement for all dissimilar connectors. For MIL-circulars all we need to change are the keying options, but for others I sometimes add extra unused pins so three 4-pins turn into a 4, 5, and 6. Also, depending on the connector line you might be able to swap a 4x1 for a 2x2 arrangement.

ak

 

Many Newbies lack what most conciser common sense, as a kid learning to fix electronics and mechanical items was a result of breaking them by misuse. Your post and choice of adjectives is a prime example of one of the many reasons their are so few electronic component suppliers that I would recommend to the budding maker/enthusiast; maybe your in the wrong business. Cute survey; you really don't have the slightest clue how to obtain relevant data or ideas. Good luck with your venture; I hate to think of the way you handle tech support.

 

WTF kind of response was that? lol. I'm not sure what you "conciser" your role to be in this world, but you certainly have no business talking down to me. What was your point, exactly? To take very little information, make sweeping presumptions in your brain and suggest you know ANYTHING at all about me, "my venture", etc?

Not that I really care, but what exactly was it about my "choice of adjectives" that provided you such worldly insights? And what does that have to do with "Component suppliers"? All-in-all... what are you on? If you've got a point, beside random Internet insults... feel free to have a lucid moment and join the conversation for real.

 

I'm on one cup of coffee; think you may of had a bit too much.... Like I said good luck with that; my role in the world is not being a D-bag with a superiority complex. If your inquiry for feedback on a common problem was phrased intelligently I would have responded with an intelligent solution. I'm not going to clarify myself further, get into a pissing match or get into any sort of measuring contest with you for various reasons.

 

@Vinny Lacorazza : Let's keep things civil. (Yes, we are watching.)

 

Weird.

Anywhoooo.... thanks for the assistance on this thread folks, with one very glaring exception lol. As I said, I really just needed a sounding board. I've got it sorted. Hey, and I did that without D-bag's "intelligent solution". Score one for the "kid learning to fix electronics and mechanical items [through] breaking them by misuse"!

 

@s_mack : Let's keep things civil, which often means letting things slide. (Yes, it's hard and, no, none of us is perfect at it -- least of all me).

 

I hear you. Water off a duck's back.