Phone Chargers

I'm willing to bet that very few manufacturers even calculate MTBF on these things. They're so inexpensive that I think your best bet is to shop by features (e.g., single, dual, or quad output), look at user reviews, and then just cross your fingers.

This adapter is one I have that actually gets carried around in my backpack:

But if you search amazon for "USB adapter" you'll get a plethora of results. I think the Apple "cube"-type adapter --

---Joel

What sort of USB connector do you want it to have; A-receptacle, miniA plug, miniB, microAB, microB?

I have accumulated several different varieties and found the "A receptacle" to be the most useful (for me) -- add an appropriate cable to connect to the device in question and it just works...

As for MTBF... consider the market that is being addressed (cell phones being essentially *disposable*) and the size involved.

Having said that, the only such "wall wart" that I have encountered defective was an Apple FireWire "charger" (and the defect was essentially mechanical -- having to do with the "fold out" AC plug not making contact, internally).

Be advised that some of these devices appear to have some smarts/logic in them. E.g., some Motogorilla products wouldn't "recognize" generic 5V USB power sources (perhaps the device talks to the charger?)

I have a DSP board I want to include in a product. It's power source is either 5-12DC on a standard power socket, or via it's mini-USB i/f. I suppose ideally I want a wallwart that has a mains lead in:-( The alternative is to put a mains socket inside the enclosure (it already has a mains cable for the other stuff in the box, a power-amp), or buy some hideously expensive PSU.

I'd get, I dunno, 10 of maybe 5 different adapters in the $1-$3 range on eBay and then send them out to beta test customers specifically asking for feedback on whether or not the adapters die. :-)

Uber-generic ones are about $1 shipped:

Although I guess I'm assuming your DSP board is pretty inexpensive here. If you're selling some fancy, multi-hundred or thousand dollar board, then I'd definitely spring for those nicer adapters with the slide-on AC connectors with the kid for Euro plugs, U.S. plugs, the honkin'-huge UK plugs, etc. Maybe something like:

As for the quality of an given adapter, I would suggest asking on bulletin boards for, e.g., Sparkfun or AVRFreaks -- a lot of the people who hang out there have some low-volume production products around, little microcontroller boards or robot controllers or whatever, and might have found some specifc adapters that are rubbish.

---Joel

.com/onetribe- Occult Talk Show

Check out a video games store such as GameStop. they sell USB wallwarts for about 10$ each in the US. I do recognize you're across the pond but I guess there is a similar store over there. My kid has one with a female USB on it and can use whatever style cable to adapt to his gizmos. Regards, al

Do some research on chargers compatibility with your particular phone/camera/iPod. Some brands (like Apple) are pretty finicky about which adapters they'll charge from. It has to do with their particular implementation of the USB standard (or some proprietary offshoot of it).

I am rapidly coming to the conclusion I will have to pay around $20 for a mains switching PSU module, eg;

"Dirk Bruere at NeoPax" kirjoitti viestissä: snipped-for-privacy@mid.individual.net...

Friwo datasheet says 200 000 hours at max load 25C ambient.

List of mobile phone charger manufacturers: Friwo

-ek

Thanks.

The older Motorola mini-USB and micro-USB phones look for a 200k resistor to ground on the sense pin. If they can't find this and can't negotiate successfully with a host computer to get permission to draw power - they don't.

Apple devices used to look for particular voltages on the D+ and D- pins of the USB socket. These were set with a pair of resistors on each pin.

Newer micro-USB phones follow the recently revised USB standard and look for a short between D+ and D-. If they detect this they assume they are connected to a charger. Otherwise they try and negotiate with a host computer for permission to take power.

The mini-USB connector is obsolete, so if you have a choice it would be better to use micro-USB in your product.

John

eg;

Try contacting Powerpax UK

John

What makes you think mini-USB connectors are obsolete?

Are DB-9 connectors obsolete too?

Yes, they were replaced with DE-9 connectors. :)

News to me too. I'd like a cite for that. We just replaced one because the vendors are constantly obsoleting various P/Ns, but there are always others.

use the

rs.

Here it is:

It turns out that they are only partially obsolete! The mini-A and mini-AB connectors have not been allowed in new USB designs since May

However, in the specific case of battery chargers, the only connectors that are permitted are standard-A receptacle or a micro-B captive cable. See section 4.1 of the USB Battery Charging Specification v1.1 which is at

John

Fair enough -- when one says "mini-USB connector" I think it's safe to say the vast majority of people are thinking "mini-B" -- mini-A and mini-AB have never been particularly common. (Especially mini-A ... mini-AB does show up on a fair number of higher-end cell phones, whereas mini-A seemed confined to a few things like digital cameras with PICTBridge printing support.)

The other thing to keep in mind is that, despite what the USB Implementers Forum guys might like, their standard has met with the kind of wild success that means that the "real" standards are now much more driven by market forces than any formal decree on their part. I mean, companies like Dell and Apple and Microsoft will definitely pay attention, but for every product they build there's some no-name company in Asia building 100 USB-connected products who'll just use whatever connector happens to be most popular and/or cheapest.

...and that's where the market forces are going against them. Their statement came out in over three years ago now, and I think it'll be several more years before battery chargers with micro-B connectors are more prevalent than those with mini-B connectors -- those companies in China cranking out thousands of them per day aren't too concerned with the official USB IF decrees. :-)

---Joel

Thanks. I printed the above out today but by the time the printer decided to work I was busy with other fires. The boss isn't going to like hitting the product, yet again. Since we own both ends of the cable, unless Mini-B connectors go away completely, there isn't much worry. ;-)

eg;

Thanks - that's obviously where Maplin get theirs from.