This is a simple project, but one I hope you will find useful. Recent upgrades of 2 of my PC’s with bang-up-to-date motherboards, have demonstrated a need for USB ‘A’ socket headers, either to fit on a standard PC Component plate, or a spare blanking panel on the front of the PC. I’ve tried sourcing 4-port versions of these and can’t find anything acceptable – hence this mini-project. The circuit is simple and the PCB matches in its’ simplicity. Below are views of the schematic & PCB, whilst the actual Eagle project files (WinRAR) are here.
|The rules for USB are simple, 4 screened lines with the screen terminated ONLY at the Host. (That’s your PC) Pin 1 on each pin-header is connected to the screen (shield) of each USB socket in turn, I’ve marked this as ‘HS’ (Header Shield) – this is better seen on the PCB – mainly because the daft Eagle library component supplied for the USB socket has no NET connection on the schematic component. The lower-right corner of the PCB (marked as a dark rectangle) should be carefully cut away after etching, to give the standard clearance for any socket on the motherboard. On my original, although I’ve designed the PCB to accept a 0.1 inch 5-way pin-header, I soldered the ends of the connecting cable to 4 sets of Cambion pin-headers on the board, on the basis that there are quite enough mechanical connections already – the choice is yours. For the connecting cable I used high-quality 4-core, individually-screened audio cable, outside diameter 4.5mm, simply because I had it to hand. I know that D- and D+ should ideally be a twisted pair, but we are talking about a very short run, from the socket to the motherboard, so it shouldn’t make any difference. (BTW I’ve used this cable on 15 metre (Long Run) USB extensions for equipment including a camera, and I’ve had no problems with it.) If you have a lighter cable, then use that as the 4.5mm diameter is slightly unwieldy. On my mother-board the connectors supplied for case-mounted USB ports are 0.1 inch 5-way double-row pin-headers, with pin 9 missing. I purchased 2 X 0.1 inch 5-way, double-row sockets for the 4 USB ports – You should verify that your connectors are the same before buying the sockets. The sockets used were intended to be mounted onto a PCB, but I simply soldered the leads of the connecting cables to the socket pins after sliding on some heat-shrink sleeving, then sliding the sleeving over the connection before warming it up with my soldering iron.|
|The Mounting Plate I’ll make a rash generalisation here, and say that everyone will have a drawer full of blank mounting plates, ’saved’ after fitting cards into every PC they’ve ever had. I do also, but I tend to use these for shim material in my metalwork shop, and in fact it’s probably better to start with a plate that already has some holes in it. In my case a good choice was an old sound-card plate, and I show this here together with the USB PCB, before I hacked the plate. I took out the intervening material (which was quite soft steel) with a small mill in my hand-held rotary tool, and finished off with a file, to give a good fit for the 4 USB socket fronts. I also made a small bracket from aluminium angle for the lower PCB fixing. On my prototype PCB (see right) I had made it so that just a small portion of the socket fronts overhung the board – I subsequently had to elongate the bracket fixing holes in the PCB because of the shortness of the top fixing bracket. I suggest trimming off a touch more of the PCB leading edge, and you won’t have the same trouble.|
|Notice that I’ve not drawn foil between the shield connections of each USB socket. Whether these should be commoned, and where they should be connected to the PC Chassis is your choice. On my new Motherboard there is a 10-pin header for each pair of USB sockets, with pin 9 missing altogether, and pin 10 marked as ‘NC’ in the GIGABYTE handbook. This is what I expected, so in my example I commoned each of the shield pads on the PCB and bridged to the topmost PCB bracket on the backplate with a 3mm solder tag. The shield of each cable is in this case Not Connected at the motherboard end, and should be insulated so as not to earth itself. Your arrangement may be different, and that’s why I’ve made the PCB as it is. I drilled holes towards the rear of the USB sockets and used cable-ties as strain relief.|