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I'm trying to decide which connector I should use for a USB peripheral I'm designing. Is there a guide for choosing one?

The device is a portable electronic scoreboard that's 16"x10"x1". It will be outside, possibly in wet conditions. It will not draw power from the USB. The only thing the USB will be used for is slow terminal serial data back and forth.

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personally apposite. thanks for the question. – antony.trupe Jan 12 '12 at 4:09
up vote 17 down vote accepted

Mini-USB is a disaster waiting to happen (in my opinion and experience).
Insertion-removal lifetime is low - one of the major factors addressed with micro-USB was an increase in cycle life.

If I was doing what you describe I would choose USB-B (ie full size) as the working choice for development and only change it if there were major reasons to. I had just this choice a few years ago and went with USB-B. The product didn't eventuate but I anticipate using it in a similar role in future.

Micro-USB is superior to Mini in many aspects. Current capacity is down in most cases but some manufacturers make (or claim) higher current versions.

Micro-USB is THE new international cellphone charging standard connector. Doesn't affect you application directly but does mean that NOT being Micro-USB compatible will prevent a few random plugins.

Regardless of what you choose, if it can get wet it should be capped in a manner that effectively gives it a formal IPxx rating that suits your need.

Mechanically, USB-B is very robust and resistant to everyday use. I have not yet seen a damaged Micro-USB connector, but they fail the-soldier proof test and probably also the hurried person in the dark test. Even USB-B would benefit from a connection guide that increases the do-it-in-the-dark connection success rate.

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Sounds good. Full size it is! – Bob Baddeley Jan 11 '12 at 21:52
I don't know where I have read it but it was quite recent that Mini-USB is near obsolete and it's rarely used in new devices - and if it's consumer's choice - Micro USB is the way to go (also a major pain in the back to solder by hand (at least the one I ordered)) – Mihailo Jan 12 '12 at 10:27

Full-Size USB B
Full-Size USB B
Full-Size USB B
Full-Size USB B
Full-Size USB B
Full-Size USB B
Full-Size USB B
Full-Size USB B
Full-Size USB B

The full-sized USB B connector is far more reliable then mini or micro B connectors.

It's also much more mechanically robust.

Really, the only valid reasons for using the Mini or Micro connectors are space-related. If you have the space for a full-sized conector, use it!

If your device is going to be used in really wet environments, Bulgin makes some very nice IP68 rated (hermetic) USB connectors.

enter image description here

Datasheet, product page.

Digikey carries them, which is nice. They're slightly expensive (well, about $25 for a mating pair), but very well made.

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I agree - for something this size then there is no reason to use delicate and fiddly connectors. I'd definitely go for a hermetically sealed one if it's for use outside in the rain. – Oli Glaser Jan 11 '12 at 18:28
+1 for USB needing some help for outdoor/side environments. – kenny Jan 11 '12 at 23:57

I'd like to point out one thing that was overlooked in other answers and that is the target audience.

We already know that mini and micro B plugs are small and therefore in some situations they are also more difficult to connect. For example if the device is going to be put in a corner somewhere and not be moved much, full size B would be easier to connect blind, that is to say without moving the device so that the receptacle can be seen (as is the case with printers for example).

Some people also may have problems using smaller USB plugs. I know lots of people who can plug a full size USB cable without even looking but must get their glasses to use mini or micro sized connector. If you don't need the space, why risk having your user curse you for putting a smaller connector in place of larger?

Another point of interest would be the design of common cables too. Full size B cables are often easier to obtain in greater length than mini or micro cables and since device is going to be outside, that could be a bonus point.

Another point that needs to be considered for a device is the flexibility of the cable itself and the mass of the device. In some cases, if the mass of the device is such that a rigid cable may move the device, it may be a good idea to use smaller connector because they often use less rigid cables.

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This is much up to what you want your product to be like. All of them will be able to pass your data equally fine, but as you know there are mechanical differences.

USB B is going to provide the strongest connection for you as far as it is difficult to accidentally pull out. However, this might also be an issue for you as someone tripping over a cable might pull the whole thing down instead of just having the cable pull out.

Mini B generally is able to hold in place better then micro B, but this depends a lot of the actual cable and plug being used.

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USB B. You aren't pressed for space. Mini B isn't used much; micro B is much more common of the two smaller versions.

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"Mini B isn't used much"... Probably 50% of the consumer electronics that I buy still have mini B – Kellenjb Jan 11 '12 at 17:31
"Mini B isn't used much" -- huh?! My GPS has Mini B. I have an audio recorder with Mini B. All of the DSP development boards I use at work either have B or Mini B. – Jason S Jan 11 '12 at 17:31
@Jason S Micro B has been mandatory for use in mobile phones sold in Europe (and China too, if I remember correctly) and I'd say that millions of those phones make a big impact. – AndrejaKo Jan 11 '12 at 17:52

Even better, you could do away with the USB connection all together and use something like a Bluetooth Serial Modem or an XBee. This has the added benefit of not needing to be in super close proximity, and there is no USB port to make waterproof.

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