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Author Topic: IF you have a dollar tree, you might wanna check it  (Read 1701 times)
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I found some 60 inch USB A to USB mini A cords in 2 of my local dollar trees perfect for arduino and most other electronic boards. Its the first time I have found a decent price on a USB cord locally. Anyway I got 5 total
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What do you have that will accept a mini-A?
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maybe I am wrong about the type, its the one that fits my phone, 2 arduino's, logic analyser, the standard small one
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 I went to the DT today after reading this post. I did not find the USB cord that I wanted but, I did find a 12v to USB converter for cigaret lighter hole it cost around a $1.

 Here comes the hack, I took it apart and found mc34063A chip inside! It is a switching power supply with a 1.5A rating, and a 40V input tolerance! I am going to test it with a motorcycle and a minimal Arduino to see if it works. I took pictures but, I still need to transfer them.

http://html.alldatasheet.com/html-pdf/92977/STMICROELECTRONICS/MC3463/1620/1/MC3463.html
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An A to mini A cable shouldn't exist (unless the full-size is female, as an adapter): mini A is for USB OTG in host mode.  Same for micro A.

I've just been doing some research on this because I want to use my phone as a host, and I'm looking into using a Linux SBC that has an OTG connector.

The mini and micro connectors have an extra "ID" pin that's grounded for A, and open for B, to tell the device whether it's supposed to be in host mode.  The A connectors are also supposed to have white plastic inside the connector, instead of black, and a different shape to the overmolding.  This appears to be routinely violated by the makers of the cheapies.  I also discovered that most of the ebay sellers have no $*&%ing clue what they're selling: they regularly mix up A and B and/or mini and micro. Some of them even mix up male and female in their descriptions.

Has anyone found a reliable source (preferably domestic U.S., for my needs) of OTG cables that doesn't charge a fortune?

Be careful if you go to Dollar Tree: I thought I'd found an A-to-mini cable there once, but it turned out to be non-standard when I got it home.
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The mini and micro connectors have an extra "ID" pin that's grounded for A, and open for B, to tell the device whether it's supposed to be in host mode.

My reading of the Wikipedia USB suggests that A and B are form factors, not having anything to do with host mode. Maybe there's a convention for host using A and non-host using B?

Supposedly, at least for some devices, the introduction of the Universal Charging Standard was supposed to eliminate a lot of this cable crap. Well, if mfrs. followed it, it would, but there's always someone <COUGH>Apple<COUGH> who just has to have a proprietary connector. I saw something just recently about how Apple has futzed again with their dock -- either locking out, or making it much harder (because someone will eventually crack it) 3rd party non-licensed devices.
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Heheh.. I was at a different dollar chain, but happened to see and grab one of those USB car adapters also, but haven't cracked it open yet.

In looking at the specsheet for the chip, it mentions current limiting.. This is particularly interesting as it would make it useful as a power LED driver.. Though I can't seem to see how to set the current limit.. But it was also only a quick look at the sheet..

Worth the buck, methinks!

(update)

Apparently it's actually common application for the chip, being used to drive power LED's.
I will see if it works and report back, if reasonably feasible...
« Last Edit: July 04, 2012, 01:24:48 pm by focalist » Logged

When the testing is complete there will be... cake.

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...found mc34063A chip inside! It is a switching power supply with a 1.5A rating, and a 40V input tolerance!

http://html.alldatasheet.com/html-pdf/92977/STMICROELECTRONICS/MC3463/1620/1/MC3463.html

 Update, I removed the female USB connections and the bits that connected to the cigarette lighter and soldered on wires in their places. I tested it with a good adjustable power supply going to the input and no load on the output although, I think the circuit has a small load resistor on it.

 Results = 7v to 25v input = 5.01v output. Not bad at all. smiley  Input < 7v makes output below 5v and somewhat unpredictable.
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...found mc34063A chip inside! It is a switching power supply with a 1.5A rating, and a 40V input tolerance!

http://html.alldatasheet.com/html-pdf/92977/STMICROELECTRONICS/MC3463/1620/1/MC3463.html

 Update, I removed the female USB connections and the bits that connected to the cigarette lighter and soldered on wires in their places. I tested it with a good adjustable power supply going to the input and no load on the output although, I think the circuit has a small load resistor on it.

 Results = 7v to 25v input = 5.01v output. Not bad at all. smiley  Input < 7v makes output below 5v and somewhat unpredictable.

That's how those circuits generally work... (keep trying to reword this and it keeps coming out sounding like a pretentious ass, which is not what I'm going for)
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  I didn't know what the minimum voltage requirement would be, so that was part of my test. Feel free to comment or add ideas, it is all welcome.  smiley
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A dollar tree is clearly not what I thought it was.
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A dollar tree is clearly not what I thought it was.
The Dollar Tree is a USA chain of stores that sells various merchandise for $1.  Mostly it is various seconds, closeouts, etc. though I suspect they may contract with various far eastern factories for their own merchandise.  There are competitor stores that sell for $0.99, etc.  I expect things bought there to fall apart in 6 months or so, but they can be useful places to harvest tools or gizmos.  But hey, if it falls apart after 6 months, it probably paid for itself.
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My reading of the Wikipedia USB suggests that A and B are form factors, not having anything to do with host mode. Maybe there's a convention for host using A and non-host using B?
It's more than a convention: it's a standard, like RS-232.  I.e., lots of people use the name without actually conforming to the specs.  smiley-mad

The Wikipedia article is incomplete: it looks like they got part of their info (like the tables of plugs and sockets) from something written after the Mini-A was deprecated.

I had to read several sources to get a complete picture.  The google search I used was something along the lines of "usb otg connector mini micro".

I should've bookmarked the best links, but I wasn't thinking about passing them on. Sorry.

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Quote
It's more than a convention: it's a standard, like RS-232. 

so theres 100 of them that no one pays attention to anymore? I honestly thought the USB plug "standards" went away way back when I saw my first 640x480 digital camera with a mini A back in the 90's

after checking yes these are A to mini A connectors just like what you need for your arduino, sony PSP, my phone and one of my (old) camera's
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My UNO has a B connector which from the Arduino site Hardware page looks standard.
My Teensy has the tiny USB plug I've come to associate with MP3 players, cameras, etc.

I don't see what the big problem about connectors is besides "it's not idiot-proofed".

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