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Project Connectors

Posted Apr 09 2013 2:48am
The world of  microminiature rectangular connector  has gotten a whole lot bigger, or smaller, depending on your prospective.

I need a connector for a new project that I am planning. The connector must be as small as possible as there is very little space on a 1 x 1.2 inch PCB.

On the PCB there will be; a stereo audio connector (for CW Keying), a push button switch, a crystal, and a 4 (or 5) pin connector which will occupy the majority of the space. The rest of the space will be used for; the Voltage Regulator and Decoupling Caps, 2N3904 RF Oscillator and Trimmer, PIC FSK Modulator, Status LED, Power Connector, and Antenna Connection. 
Most of the resistors will be of size 0603, and cap's will be 0804 mils, most traces will be 8/8 mils.
Why not make the PCB larger you ask?     Well, . . . I just like to make things as small as I can - just because I think I can.

The two connectors that I am considering using for this project are; the "Mini" or the "Micro" USB connectors. These are the smallest connectors that I have found. I know this will violate the "standards", by using them in this way, but it is my personal project and I will just have to not plug them into a standard USB fixture or cable.

In researching these connectors, I have learned a lot about the USB standards, and what that means for use with our smart phones and personal devices. A couple of things that I have learned are:
We have China to thank for requiring the "standard" "Micro" charger and data transfer connectors on our new cell phones (and personal devices), they said make the charger standard or do not try to sell it in China (Why couldn't we have done that?). And yes, the standard is the new smaller "Micro" connector and not the "Mini" connector that is currently found on our "slightly" older personal devices.
The first (and much larger) standard USB "A" and "B" connectors use four wires; +5 Volts, Gnd, +Data and -Data. The large flat "A" connector is normal found on the side of computers, and the smaller almost square "B" connector is normally used on peripherals. The connector establish the "Master/Slave" communication protocol.
Adapters cables with one large "A" connector are available for connection to a second small "Mini" and "Micro" connectors. These smaller connectors have five (5) pins for connection, the first four (4) are the same as the larger USB "A" and "B" connectors, on some hardware the fifth pin is shorted to ground to indicate which device is to be, "Master" or "Slave" ( I don't remember the details of which is which). Also, the standard requires that only one data connector is allowed on any new personal device (Note, a second connector is allowed, but it can only be used for additional power). UPDATE: the new pin was added at position number 4, old pin 4 became pin five, see the wikipedia
The designators for these "Mini" and "Micro" connectors are "AB" and "B". The "AB" connector is rectangular and accepts both the "AB" and "B" male plugs, The "B" connector accepts the "B" plug and has corner notches as to reject the "AB" male plug.
The current China Standard is the "Micro" connector (below) for all new personal devices. It is similar to the "Mini" connector (above), but about 1/2 the size (unlike the included drawings would imply).
The good news is; because the USB connector is not only for data transfer, it also used for device battery "charging", so we now have a "auto and home" charging standard for personal devices - we are no longer condemned to multiple charger-cord hell. Now we have one charging cord plug standard for all new personal devices. I have been told that many new cars now have USB charging connectors as standard equipment.
What does this mean for my project; "Mini" cables and Connectors are available in surplus and new stock, and because they are no longer new, and now a deprecated standard,  . . .  so now - I am going to use them in my projects of  connector solution  !

This HomeBrew project (and similar follow-on projects) will be used as an Transmit Exciter for the QRP HF PA as planned in a previous post.

I will provide more details as my Home Brew Project continues.
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